title: Moon

text: The Moon is the second-densest satellite in the Solar System, after Io. However, the inner core of the Moon is small, with a radius of about or less, around 20% of the radius of the Moon. Its composition is not well understood, but is probably metallic iron alloyed with a small amount of sulfur and nickel; analyses of the Moon's time-variable rotation suggest that it is at least partly molten. The pressure at the lunar core is estimated to be .


title: Moon

text: The Moon has an external magnetic field of less than 0.2 nanoteslas, or less than one hundred thousandth that of Earth. The Moon does not currently have a global dipolar magnetic field and only has crustal magnetization likely acquired early in its history when a dynamo was still operating. However, early in its history, 4 billion years ago, its magnetic field strength was likely close to that of Earth today. This early dynamo field apparently expired by about one billion years ago, after the lunar core had completely crystallized. Theoretically, some of the remnant magnetization may originate from transient magnetic fields generated during large impacts through the expansion of plasma clouds. These clouds are generated during large impacts in an ambient magnetic field. This is supported by the location of the largest crustal magnetizations situated near the antipodes of the giant impact basins.


title: Moon

text: On average the Moon's surface gravity is (; ), about half of the surface gravity of Mars and about a sixth of Earth's. The Moon's gravitational field is not uniform. The details of the gravitational field have been measured through tracking the Doppler shift of radio signals emitted by orbiting spacecraft. The main lunar gravity features are mascons, large positive gravitational anomalies associated with some of the giant impact basins, partly caused by the dense mare basaltic lava flows that fill those basins. The anomalies greatly influence the orbit of spacecraft about the Moon. There are some puzzles: lava flows by themselves cannot explain all of the gravitational signature, and some mascons exist that are not linked to mare volcanism.


title: Moon

text: The Moon has an atmosphere so tenuous as to be nearly vacuum, with a total mass of less than . The surface pressure of this small mass is around 3 × 10 atm (0.3 nPa); it varies with the lunar day. Its sources include outgassing and sputtering, a product of the bombardment of lunar soil by solar wind ions. Elements that have been detected include sodium and potassium, produced by sputtering (also found in the atmospheres of Mercury and Io); helium-4 and neon from the solar wind; and argon-40, radon-222, and polonium-210, outgassed after their creation by radioactive decay within the crust and mantle. The absence of such neutral species (atoms or molecules) as oxygen, nitrogen, carbon, hydrogen and magnesium, which are present in the regolith, is not understood. Water vapor has been detected by "Chandrayaan-1" and found to vary with latitude, with a maximum at ~60–70 degrees; it is possibly generated from the sublimation of water ice in the regolith. These gases either return into the regolith because of the Moon's gravity or are lost to space, either through solar radiation pressure or, if they are ionized, by being swept away by the solar wind's magnetic field.


title: Moon

text: Studies of Moon magma samples retrieved by the Apollo missions demonstrate that the Moon had once possessed a relatively thick atmosphere for a period of 70 million years between 3 and 4 billion years ago. This atmosphere, sourced from gases ejected from lunar volcanic eruptions, was twice the thickness of that of present-day Mars. The ancient lunar atmosphere was eventually stripped away by solar winds and dissipated into space.


title: Moon

text: A permanent Moon dust cloud exists around the Moon, generated by small particles from comets. Estimates are 5 tons of comet particles strike the Moon's surface every 24 hours, resulting in the ejection of dust particles. The dust stays above the Moon approximately 10 minutes, taking 5 minutes to rise, and 5 minutes to fall. On average, 120 kilograms of dust are present above the Moon, rising up to 100 kilometers above the surface. Dust counts made by LADEE's Lunar Dust EXperiment (LDEX) found particle counts peaked during the Geminid, Quadrantid, Northern Taurid, and Omicron Centaurid meteor showers, when the Earth, and Moon pass through comet debris. The lunar dust cloud is asymmetric, being more dense near the boundary between the Moon's dayside and nightside.


title: Moon

text: Ionizing radiation from cosmic rays, the Sun and the resulting neutron radiation produce radiation levels on average of 1,369 microsieverts per day, which is about 2-3 times more than on the International Space Station at about 400 km above Earth in orbit, 5-10 times more than during a trans-Atlantic flight, 200 times more than on Earth's surface. For further comparison radiation on a flight to Mars is about 1.84 millisieverts per day and on Mars 0.64 millisieverts per day.


title: Moon

text: The Moon's axial tilt with respect to the ecliptic is only 1.5427°, much less than the 23.44° of Earth. Because of this small tilt, the Moon's solar illumination varies much less with season than on Earth and it allows for the existence of some peaks of eternal light at the Moon's north pole, at the rim of the crater Peary.


title: Moon

text: The surface is exposed to drastic temperature differences ranging from to depending on the solar irradiance.


title: Moon

text: Because of the lack of atmosphere, temperatures of different areas vary particularly upon whether they are in sunlight or shadow, making topographical details play a decisive role on local surface temperatures.


title: Moon

text: Parts of many craters, particularly the bottoms of many polar craters, are permanently shadowed, these "craters of eternal darkness" have extremely low temperatures. The "Lunar Reconnaissance Orbiter" measured the lowest summer temperatures in craters at the southern pole at and just close to the winter solstice in the north polar crater Hermite. This is the coldest temperature in the Solar System ever measured by a spacecraft, colder even than the surface of Pluto.


title: Moon

text: Blanketed on top of the Moon's crust is a highly comminuted (broken into ever smaller particles) and impact gardened mostly gray surface layer called regolith, formed by impact processes. The finer regolith, the lunar soil of silicon dioxide glass, has a texture resembling snow and a scent resembling spent gunpowder. The regolith of older surfaces is generally thicker than for younger surfaces: it varies in thickness from in the highlands and in the maria. Beneath the finely comminuted regolith layer is the "megaregolith", a layer of highly fractured bedrock many kilometers thick.


title: Moon

text: These extreme conditions for example are considered making it unlikely for spacecrafts to harbor bacterial spores at the Moon longer than just one lunar orbit.


title: Moon

text: The topography of the Moon has been measured with laser altimetry and stereo image analysis. Its most extensive topographic feature is the giant far-side South Pole–Aitken basin, some in diameter, the largest crater on the Moon and the second-largest confirmed impact crater in the Solar System. At deep, its floor is the lowest point on the surface of the Moon. The highest elevations of the Moon's surface are located directly to the northeast, which might have been thickened by the oblique formation impact of the South Pole–Aitken basin. Other large impact basins such as Imbrium, Serenitatis, Crisium, Smythii, and Orientale possess regionally low elevations and elevated rims. The far side of the lunar surface is on average about higher than that of the near side.


title: Moon

text: The discovery of fault scarp cliffs suggest that the Moon has shrunk by about 90 metres (300 ft) within the past billion years. Similar shrinkage features exist on Mercury. Mare Frigoris, a basin near the north pole long assumed to be geologically dead, has cracked and shifted. Since the Moon doesn't have tectonic plates, its tectonic activity is slow and cracks develop as it loses heat.


title: Moon

text: The main features visible from Earth by the naked eye are dark and relatively featureless lunar plains called "maria" (singular "mare"; Latin for "seas", as they were once believed to be filled with water) are vast solidified pools of ancient basaltic lava. Although similar to terrestrial basalts, lunar basalts have more iron and no minerals altered by water. The majority of these lava deposits erupted or flowed into the depressions associated with impact basins. Several geologic provinces containing shield volcanoes and volcanic domes are found within the near side "maria".


title: Moon

text: Almost all maria are on the near side of the Moon, and cover 31% of the surface of the near side compared with 2% of the far side. This is likely due to a concentration of heat-producing elements under the crust on the near side, which would have caused the underlying mantle to heat up, partially melt, rise to the surface and erupt. Most of the Moon's mare basalts erupted during the Imbrian period, 3.3–3.7 billion years ago, though some being as young as 1.2 billion years and as old as 4.2 billion years.


title: Moon

text: In 2006, a study of Ina, a tiny depression in Lacus Felicitatis, found jagged, relatively dust-free features that, because of the lack of erosion by infalling debris, appeared to be only 2 million years old. Moonquakes and releases of gas indicate continued lunar activity. Evidence of recent lunar volcanism has been identified at 70 irregular mare patches, some less than 50 million years old. This raises the possibility of a much warmer lunar mantle than previously believed, at least on the near side where the deep crust is substantially warmer because of the greater concentration of radioactive elements. Evidence has been found for 2–10 million years old basaltic volcanism within the crater Lowell, inside the Orientale basin. Some combination of an initially hotter mantle and local enrichment of heat-producing elements in the mantle could be responsible for prolonged activities on the far side in the Orientale basin.


title: Moon

text: The lighter-colored regions of the Moon are called "terrae", or more commonly "highlands", because they are higher than most maria. They have been radiometrically dated to having formed 4.4 billion years ago, and may represent plagioclase cumulates of the lunar magma ocean. In contrast to Earth, no major lunar mountains are believed to have formed as a result of tectonic events.


title: Moon

text: The concentration of maria on the near side likely reflects the substantially thicker crust of the highlands of the Far Side, which may have formed in a slow-velocity impact of a second moon of Earth a few tens of millions of years after the Moon's formation. Alternatively, it may be a consequence of asymmetrical tidal heating when the Moon was much closer to the Earth.


title: Moon

text: A major geologic process that has affected the Moon's surface is impact cratering, with craters formed when asteroids and comets collide with the lunar surface. There are estimated to be roughly 300,000 craters wider than on the Moon's near side. The lunar geologic timescale is based on the most prominent impact events, including Nectaris, Imbrium, and Orientale; structures characterized by multiple rings of uplifted material, between hundreds and thousands of kilometers in diameter and associated with a broad apron of ejecta deposits that form a regional stratigraphic horizon. The lack of an atmosphere, weather, and recent geological processes mean that many of these craters are well-preserved. Although only a few multi-ring basins have been definitively dated, they are useful for assigning relative ages. Because impact craters accumulate at a nearly constant rate, counting the number of craters per unit area can be used to estimate the age of the surface. The radiometric ages of impact-melted rocks collected during the Apollo missions cluster between 3.8 and 4.1 billion years old: this has been used to propose a Late Heavy Bombardment period of increased impacts.


title: Moon

text: High-resolution images from the Lunar Reconnaissance Orbiter in the 2010s show a contemporary crater-production rate significantly higher than was previously estimated. A secondary cratering process caused by distal ejecta is thought to churn the top two centimeters of regolith on a timescale of 81,000 years. This rate is 100 times faster than the rate computed from models based solely on direct micrometeorite impacts.


title: Moon

text: Lunar swirls are enigmatic features found across the Moon's surface. They are characterized by a high albedo, appear optically immature (i.e. the optical characteristics of a relatively young regolith), and often have a sinuous shape. Their shape is often accentuated by low albedo regions that wind between the bright swirls. They are located in places with enhanced surface magnetic fields and many are located at the antipodal point of major impacts. Well known swirls include the Reiner Gamma feature and Mare Ingenii. They are hypothesized to be areas that have been partially shielded from the solar wind, resulting in slower space weathering.


title: Moon

text: Liquid water cannot persist on the lunar surface. When exposed to solar radiation, water quickly decomposes through a process known as photodissociation and is lost to space. However, since the 1960s, scientists have hypothesized that water ice may be deposited by impacting comets or possibly produced by the reaction of oxygen-rich lunar rocks, and hydrogen from solar wind, leaving traces of water which could possibly persist in cold, permanently shadowed craters at either pole on the Moon. Computer simulations suggest that up to of the surface may be in permanent shadow. The presence of usable quantities of water on the Moon is an important factor in rendering lunar habitation as a cost-effective plan; the alternative of transporting water from Earth would be prohibitively expensive.


title: Moon

text: In years since, signatures of water have been found to exist on the lunar surface. In 1994, the bistatic radar experiment located on the "Clementine" spacecraft, indicated the existence of small, frozen pockets of water close to the surface. However, later radar observations by Arecibo, suggest these findings may rather be rocks ejected from young impact craters. In 1998, the neutron spectrometer on the "Lunar Prospector" spacecraft showed that high concentrations of hydrogen are present in the first meter of depth in the regolith near the polar regions. Volcanic lava beads, brought back to Earth aboard Apollo 15, showed small amounts of water in their interior.


title: Moon

text: The 2008 "Chandrayaan-1" spacecraft has since confirmed the existence of surface water ice, using the on-board Moon Mineralogy Mapper. The spectrometer observed absorption lines common to hydroxyl, in reflected sunlight, providing evidence of large quantities of water ice, on the lunar surface. The spacecraft showed that concentrations may possibly be as high as 1,000 ppm. Using the mapper's reflectance spectra, indirect lighting of areas in shadow confirmed water ice within 20° latitude of both poles in 2018. In 2009, "LCROSS" sent a impactor into a permanently shadowed polar crater, and detected at least of water in a plume of ejected material. Another examination of the LCROSS data showed the amount of detected water to be closer to .


title: Moon

text: In May 2011, 615–1410 ppm water in melt inclusions in lunar sample 74220 was reported, the famous high-titanium "orange glass soil" of volcanic origin collected during the Apollo 17 mission in 1972. The inclusions were formed during explosive eruptions on the Moon approximately 3.7 billion years ago. This concentration is comparable with that of magma in Earth's upper mantle. Although of considerable selenological interest, this insight does not mean that water is easily available since the sample originated many kilometers below the surface, and the inclusions are so difficult to access that it took 39 years to find them with a state-of-the-art ion microprobe instrument.


title: Moon

text: Analysis of the findings of the Moon Mineralogy Mapper (M3) revealed in August 2018 for the first time "definitive evidence" for water-ice on the lunar surface. The data revealed the distinct reflective signatures of water-ice, as opposed to dust and other reflective substances. The ice deposits were found on the North and South poles, although it is more abundant in the South, where water is trapped in permanently shadowed craters and crevices, allowing it to persist as ice on the surface since they are shielded from the sun.


title: Moon

text: In October 2020, astronomers reported detecting molecular water on the sunlit surface of the Moon by several independent spacecraft, including the Stratospheric Observatory for Infrared Astronomy (SOFIA).


title: Moon

text: The Earth and the Moon form the Earth-Moon satellite system with a shared center of mass, or barycenter. This barycenter stays located at all times (about a quarter of Earth's radius) beneath the Earth's surface, making the Moon seemingly orbit the Earth.


title: Moon

text: The Lunar distance, or the semi-major axis of the geocentric lunar orbit, is approximately 400,000 km, which is a quarter of a million miles or 1.28 light-seconds, and a unit of measure in astronomy. This is not to be confused with the instantaneous Earth–Moon distance, or distance to the Moon, the momentanous distance from the center of Earth to the center of the Moon.


title: Moon

text: The Moon makes a complete orbit around Earth with respect to the fixed stars, its sidereal period, about once every 27.3 days. However, because the Earth-Moon system moves at the same time in its orbit around the Sun, it takes slightly longer, 29.5 days;, to return at the same lunar phase, completing a full cycle, as seen from Earth. This synodic period or synodic month is commonly known as the lunar month and is equal to the length of the solar day on the Moon.


title: Moon

text: Due to tidal locking, the Moon has a 1:1 spin–orbit resonance. This rotation–orbit ratio makes the Moon's orbital periods around Earth equal to its corresponding rotation periods. This is the reason for only one side of the Moon, its so-called near side, being visible from Earth. That said, while the movement of the Moon is in resonance, it still is not without nuances such as libration, resulting in slightly changing perspectives, making over time and location on Earth about 59% of the Moon's surface visible from Earth.


title: Moon

text: Unlike most satellites of other planets, the Moon's orbital plane is closer to the ecliptic plane than to the planet's equatorial plane. The Moon's orbit is subtly perturbed by the Sun and Earth in many small, complex and interacting ways. For example, the plane of the Moon's orbit gradually rotates once every 18.61years, which affects other aspects of lunar motion. These follow-on effects are mathematically described by Cassini's laws.


title: Moon

text: The gravitational attraction that Earth and the Moon (as well as the Sun) exert on each other manifests in a slightly greater attraction on the sides of closest to each other, resulting in tidal forces. Ocean tides are the most widely experienced result of this, but tidal forces considerably affect also other mechanics of Earth, as well as the Moon and their system.


title: Moon

text: The lunar solid crust experiences tides of around amplitude over 27 days, with three components: a fixed one due to Earth, because they are in synchronous rotation, a variable tide due to orbital eccentricity and inclination, and a small varying component from the Sun. The Earth-induced variable component arises from changing distance and libration, a result of the Moon's orbital eccentricity and inclination (if the Moon's orbit were perfectly circular and un-inclined, there would only be solar tides). According to recent research, scientists suggest that the Moon's influence on the Earth may contribute to maintaining Earth's magnetic field.


title: Moon

text: The cumulative effects of stress built up by these tidal forces produces moonquakes. Moonquakes are much less common and weaker than are earthquakes, although moonquakes can last for up to an hour – significantly longer than terrestrial quakes – because of scattering of the seismic vibrations in the dry fragmented upper crust. The existence of moonquakes was an unexpected discovery from seismometers placed on the Moon by Apollo astronauts from 1969 through 1972.


title: Moon

text: The most commonly known effect of tidal forces are elevated sea levels called ocean tides. While the Moon exerts most of the tidal forces, the Sun also exerts tidal forces and therefore contributes to the tides as much as 40% of the Moon's tidal force; producing in interplay the spring and neap tides.


title: Moon

text: The tides are two bulges in the Earth's oceans, one on the side facing the Moon and the other on the side opposite. As the Earth rotates on its axis, one of the ocean bulges (high tide) is held in place "under" the Moon, while another such tide is opposite. As a result, there are two high tides, and two low tides in about 24 hours. Since the Moon is orbiting the Earth in the same direction of the Earth's rotation, the high tides occur about every 12 hours and 25 minutes; the 25 minutes is due to the Moon's time to orbit the Earth.


title: Moon

text: If the Earth were a water world (one with no continents) it would produce a tide of only one meter, and that tide would be very predictable, but the ocean tides are greatly modified by other effects:


title: Moon

text: As a result, the timing of the tides at most points on the Earth is a product of observations that are explained, incidentally, by theory.


title: Moon

text: Delays in the tidal peaks of both ocean and solid-body tides cause torque in opposition to the Earth's rotation. This "drains" angular momentum and rotational kinetic energy from Earth's rotation, slowing the Earth's rotation. That angular momentum, lost from the Earth, is transferred to the Moon in a process known as tidal acceleration, which lifts the Moon into a higher orbit while lowering orbital speed around the Earth.


title: Moon

text: Thus the distance between Earth and Moon is increasing, and the Earth's rotation is slowing in reaction. Measurements from laser reflectors left during the Apollo missions (lunar ranging experiments) have found that the Moon's distance increases by per year (roughly the rate at which human fingernails grow).


title: Moon

text: Atomic clocks show that Earth's day lengthens by about 17 microseconds every year, slowly increasing the rate at which UTC is adjusted by leap seconds.


title: Moon

text: This tidal drag makes the rotation of Earth and the orbital period of the Moon very slowly match. This matching first results in tidally locking the lighter body of the orbital system, as already the case with the Moon. Eventually, after 50 billion years, also the Earth would be made to always face the Moon with the same side, though the Sun will become a red giant engulfing the Earth-Moon system long before the latter occurs.


title: Moon

text: The Moon's highest altitude at culmination varies by its lunar phase, or more correctly its orbital position, and time of the year, or more correctly the position of the Earth's axis. The full moon is highest in the sky during winter and lowest during summer (for each hemisphere respectively), with its altitude changing towards dark moon to the opposite.


title: Moon

text: At the North and South Poles the Moon is 24 hours above the horizon for two weeks every tropical month (about 27.3 days), comparable to the polar day of the tropical year. Zooplankton in the Arctic use moonlight when the Sun is below the horizon for months on end.


title: Moon

text: The apparent orientation of the Moon depends on its position in the sky and the hemisphere of the Earth from which it is being viewed. In the northern hemisphere it is seen upside down compared to the view in the southern hemisphere. Sometimes the "horns" of a crescent moon appear to be pointing more upwards than sideways. This phenomenon is called a wet moon and occurs more frequently in the tropics.


title: Moon

text: The distance between the Moon and Earth varies from around to at perigee (closest) and apogee (farthest), respectively, making the Moon's apparent size fluctuate. On sverage the Moon's angular diameter is about 0.52° (on average) in the sky, roughly the same apparent size as the Sun (see ). Additionally when close to the horizon a purely psychological effect, known as the Moon illusion, makes the Moon appear larger.


title: Moon

text: Despite the Moon's tidal locking, the effect of libration makes about 59% of the Moon's surface visible from Earth over the course of one month.


title: Moon

text: The tidally locked synchronous rotation of the Moon as it orbits the Earth results in it always keeping nearly the same face turned towards the planet. The side of the Moon that faces Earth is called the near side, and the opposite the far side. The far side is often inaccurately called the "dark side", but it is in fact illuminated as often as the near side: once every 29.5 Earth days. During dark moon to new moon, the near side is dark.


title: Moon

text: The Moon originally rotated at a faster rate, but early in its history its rotation slowed and became tidally locked in this orientation as a result of frictional effects associated with tidal deformations caused by Earth. With time, the energy of rotation of the Moon on its axis was dissipated as heat, until there was no rotation of the Moon relative to Earth. In 2016, planetary scientists using data collected on the 1998-99 NASA "Lunar Prospector" mission, found two hydrogen-rich areas (most likely former water ice) on opposite sides of the Moon. It is speculated that these patches were the poles of the Moon billions of years ago before it was tidally locked to Earth.


title: Moon

text: Half of the Moon's surface is always illuminated by the Sun (except during a lunar eclipse). Earth also reflects light onto the Moon, observable at times as Earthlight when it is again reflected back to Earth from areas of the near side of the Moon that are not illuminated by the Sun.


title: Moon

text: With the different positions of the Moon, different areas of it are illuminated by the Sun. This illumination of different lunar areas, as viewed from Earth, produces the different lunar phases during the synodic month. A phase is equal to the area of the visible lunar sphere that is illuminated by the Sun. This area or "degree of illumination" is given by formula_1, where formula_2 is the elongation (i.e., the angle between Moon, the observer on Earth, and the Sun).


title: Moon

text: On 14 November 2016, the Moon was at full phase closer to Earth than it had been since 1948. It was 14% closer and larger than its farthest position in apogee. This closest point coincided within an hour of a full moon, and it was 30% more luminous than when at its greatest distance because of its increased apparent diameter, which made it a particularly notable example of a "supermoon".


title: Moon

text: At lower levels, the human perception of reduced brightness as a percentage is provided by the following formula:


title: Moon

text: When the actual reduction is 1.00 / 1.30, or about 0.770, the perceived reduction is about 0.877, or 1.00 / 1.14. This gives a maximum perceived increase of 14% between apogee and perigee moons of the same phase.


title: Moon

text: The Moon has an exceptionally low albedo, giving it a reflectance that is slightly brighter than that of worn asphalt. Despite this, it is the brightest object in the sky after the Sun. This is due partly to the brightness enhancement of the opposition surge; the Moon at quarter phase is only one-tenth as bright, rather than half as bright, as at full moon. Additionally, color constancy in the visual system recalibrates the relations between the colors of an object and its surroundings, and because the surrounding sky is comparatively dark, the sunlit Moon is perceived as a bright object. The edges of the full moon seem as bright as the center, without limb darkening, because of the reflective properties of lunar soil, which retroreflects light more towards the Sun than in other directions. The Moon's color depends on the light the Moon reflects, which in turn depends on the Moon's surface and its features, having for example large darker regions. In general the lunar surface reflects a brown-tinged gray light.


title: Moon

text: Viewed from Earth the air filters the reflected light, at times giving it a red color depending on the angle of the Moon in the sky and thickness of the atmosphere, or a blue tinge depending on the particles in the air, as in cases of volcanic particles. The terms blood moon and blue moon do not necessarily refer to circumstances of red or blue moonlight, but are rather particular cultural references such as particular full moons of a year.


title: Moon

text: There has been historical controversy over whether observed features on the Moon's surface change over time. Today, many of these claims are thought to be illusory, resulting from observation under different lighting conditions, poor astronomical seeing, or inadequate drawings. However, outgassing does occasionally occur and could be responsible for a minor percentage of the reported lunar transient phenomena. Recently, it has been suggested that a roughly diameter region of the lunar surface was modified by a gas release event about a million years ago.


title: Moon

text: Eclipses only occur when the Sun, Earth, and Moon are all in a straight line (termed "syzygy"). Solar eclipses occur at new moon, when the Moon is between the Sun and Earth. In contrast, lunar eclipses occur at full moon, when Earth is between the Sun and Moon. The apparent size of the Moon is roughly the same as that of the Sun, with both being viewed at close to one-half a degree wide. The Sun is much larger than the Moon but it is the vastly greater distance that gives it the same apparent size as the much closer and much smaller Moon from the perspective of Earth. The variations in apparent size, due to the non-circular orbits, are nearly the same as well, though occurring in different cycles. This makes possible both total (with the Moon appearing larger than the Sun) and annular (with the Moon appearing smaller than the Sun) solar eclipses. In a total eclipse, the Moon completely covers the disc of the Sun and the solar corona becomes visible to the naked eye. Because the distance between the Moon and Earth is very slowly increasing over time, the angular diameter of the Moon is decreasing. As it evolves toward becoming a red giant, the size of the Sun, and its apparent diameter in the sky, are slowly increasing. The combination of these two changes means that hundreds of millions of years ago, the Moon would always completely cover the Sun on solar eclipses, and no annular eclipses were possible. Likewise, hundreds of millions of years in the future, the Moon will no longer cover the Sun completely, and total solar eclipses will not occur.


title: Moon

text: Because the Moon's orbit around Earth is inclined by about 5.145° (5° 9') to the orbit of Earth around the Sun, eclipses do not occur at every full and new moon. For an eclipse to occur, the Moon must be near the intersection of the two orbital planes. The periodicity and recurrence of eclipses of the Sun by the Moon, and of the Moon by Earth, is described by the saros, which has a period of approximately 18 years.


title: Moon

text: Because the Moon continuously blocks the view of a half-degree-wide circular area of the sky, the related phenomenon of occultation occurs when a bright star or planet passes behind the Moon and is occulted: hidden from view. In this way, a solar eclipse is an occultation of the Sun. Because the Moon is comparatively close to Earth, occultations of individual stars are not visible everywhere on the planet, nor at the same time. Because of the precession of the lunar orbit, each year different stars are occulted.


title: Moon

text: It is believed by some that 20–30,000 year old tally sticks, were used to observe the phases of the Moon, keeping time using the waxing and waning of the Moon's phases.


title: Moon

text: One of the earliest-discovered possible depictions of the Moon is a 5000-year-old rock carving "Orthostat 47" at Knowth, Ireland.


title: Moon

text: The ancient Greek philosopher Anaxagoras () reasoned that the Sun and Moon were both giant spherical rocks, and that the latter reflected the light of the former. Elsewhere in the to , Babylonian astronomers had recorded the 18-year Saros cycle of lunar eclipses, and Indian astronomers had described the Moon's monthly elongation. The Chinese astronomer Shi Shen gave instructions for predicting solar and lunar eclipses.


title: Moon

text: In Aristotle's (384–322 BC) description of the universe, the Moon marked the boundary between the spheres of the mutable elements (earth, water, air and fire), and the imperishable stars of aether, an influential philosophy that would dominate for centuries. Archimedes (287–212 BC) designed a planetarium that could calculate the motions of the Moon and other objects in the Solar System. In the , Seleucus of Seleucia correctly theorized that tides were due to the attraction of the Moon, and that their height depends on the Moon's position relative to the Sun. In the same century, Aristarchus computed the size and distance of the Moon from Earth, obtaining a value of about twenty times the radius of Earth for the distance.


title: Moon

text: Although the Chinese of the Han Dynasty believed the Moon to be energy equated to "qi", their 'radiating influence' theory recognized that the light of the Moon was merely a reflection of the Sun, and Jing Fang (78–37 BC) noted the sphericity of the Moon. Ptolemy (90–168 AD) greatly improved on the numbers of Aristarchus, calculating the values of a mean distance of 59 times Earth's radius and a diameter of 0.292 Earth diameters were close to the correct values of about 60 and 0.273 respectively. In the 2nd century AD, Lucian wrote the novel "A True Story", in which the heroes travel to the Moon and meet its inhabitants. In 499 AD, the Indian astronomer Aryabhata mentioned in his "Aryabhatiya" that reflected sunlight is the cause of the shining of the Moon. The astronomer and physicist Alhazen (965–1039) found that sunlight was not reflected from the Moon like a mirror, but that light was emitted from every part of the Moon's sunlit surface in all directions. Shen Kuo (1031–1095) of the Song dynasty created an allegory equating the waxing and waning of the Moon to a round ball of reflective silver that, when doused with white powder and viewed from the side, would appear to be a crescent.


title: Moon

text: During the Middle Ages, before the invention of the telescope, the Moon was increasingly recognised as a sphere, though many believed that it was "perfectly smooth".


title: Moon

text: In 1609, Galileo Galilei used an early telescope to make drawings of the Moon for his book , and deduced that it was not smooth but had mountains and craters. Thomas Harriot had made, but not published such drawings a few months earlier.


title: Moon

text: Telescopic mapping of the Moon followed: later in the 17th century, the efforts of Giovanni Battista Riccioli and Francesco Maria Grimaldi led to the system of naming of lunar features in use today. The more exact 1834–1836 of Wilhelm Beer and Johann Heinrich Mädler, and their associated 1837 book , the first trigonometrically accurate study of lunar features, included the heights of more than a thousand mountains, and introduced the study of the Moon at accuracies possible in earthly geography. Lunar craters, first noted by Galileo, were thought to be volcanic until the 1870s proposal of Richard Proctor that they were formed by collisions. This view gained support in 1892 from the experimentation of geologist Grove Karl Gilbert, and from comparative studies from 1920 to the 1940s, leading to the development of lunar stratigraphy, which by the 1950s was becoming a new and growing branch of astrogeology.


title: Moon

text: After World War II the first launch systems were developed and by the end of the 1950s they reached capabilities that allowed the Soviet Union and the United States to launch spacecrafts into space. The Cold War fueled a closely followed development of launch systems by the two states, resulting in the so-called Space Race and its later phase the Moon Race, accelerating efforts and interest in exploration of the Moon.


title: Moon

text: After the first spaceflight of Sputnik 1 in 1957 during International Geophysical Year the spacecrafts of the Soviet Union's "Luna" program were the first to accomplish a number of goals. Following three unnamed failed missions in 1958, the first human-made object "Luna 1" escaped Earth's gravity and passed near the Moon in 1959. Later that year the first human-made object "Luna 2" reached the Moon's surface by intentionally impacting. By the end of the year "Luna 3" reached as the first human-made object the normally occluded far side of the Moon, taking the first photographs of it.


title: Moon

text: The first spacecraft to perform a successful lunar soft landing was "Luna 9" and the first vehicle to orbit the Moon was "Luna 10", both in 1966.


title: Moon

text: Following President John F. Kennedy's 1961 commitment to a manned Moon landing before the end of the decade, the United States, under NASA leadership, launched a series of uncrewed probes to develop an understanding of the lunar surface in preparation for human missions: the Jet Propulsion Laboratory's Ranger program, the Lunar Orbiter program and the Surveyor program. The crewed Apollo program was developed in parallel; after a series of uncrewed and crewed tests of the Apollo spacecraft in Earth orbit, and spurred on by a potential Soviet lunar human landing, in 1968 Apollo 8 made the first human mission to lunar orbit. The subsequent landing of the first humans on the Moon in 1969 is seen by many as the culmination of the Space Race.


title: Moon

text: Neil Armstrong became the first person to walk on the Moon as the commander of the American mission Apollo 11 by first setting foot on the Moon at 02:56 UTC on 21 July 1969. An estimated 500 million people worldwide watched the transmission by the Apollo TV camera, the largest television audience for a live broadcast at that time. The Apollo missions 11 to 17 (except Apollo 13, which aborted its planned lunar landing) removed of lunar rock and soil in 2,196 separate samples.


title: Moon

text: Scientific instrument packages were installed on the lunar surface during all the Apollo landings. Long-lived instrument stations, including heat flow probes, seismometers, and magnetometers, were installed at the Apollo 12, 14, 15, 16, and 17 landing sites. Direct transmission of data to Earth concluded in late 1977 because of budgetary considerations, but as the stations' lunar laser ranging corner-cube retroreflector arrays are passive instruments, they are still being used.


title: Moon

text: Apollo 17 in 1972 remains the last crewed mission to the Moon. Explorer 49 in 1973 was the last dedicated U.S. probe to the Moon until the 1990s.


title: Moon

text: The Soviet Union continued sending robotic missions to the Moon until 1976, deploying in 1970 with Luna 17 the first remote controlled rover Lunokhod 1 on an extraterrestrial surface, and collecting and returning 0.3 kg of rock and soil samples with three "Luna" sample return missions ("Luna 16" in 1970, "Luna 20" in 1972, and "Luna 24" in 1976).


title: Moon

text: A near lunar quietude of fourteen years followed the last Soviet mission to the Moon of 1976. Astronautics had shifted its focus towards the exploration of the inner (e.g. Venera program) and outer (e.g. Pioneer 10, 1972) Solar System planets, but also towards Earth orbit, developing and continuously operating, beside communication satellites, Earth observation satellites (e.g. Landsat program, 1972) space telescopes and particularly space stations (e.g. Salyut program, 1971).


title: Moon

text: The until 1979 negotiated Moon treaty, with its ratification in 1984 by its few signatories was about the only major activity regarding the Moon until 1990.


title: Moon

text: In 1990 "Hiten"-"Hagoromo", the first dedicated lunar mission since 1976, reached the Moon. Sent by Japan, it became the first mission that was not a Soviet Union or U.S. mission to the Moon.


title: Moon

text: In 1994, the U.S. dedicated a mission to fly a spacecraft ("Clementine") to the Moon again for the first time since 1973. This mission obtained the first near-global topographic map of the Moon, and the first global multispectral images of the lunar surface. In 1998 this was followed by the "Lunar Prospector" mission, whose instruments indicated the presence of excess hydrogen at the lunar poles, which is likely to have been caused by the presence of water ice in the upper few meters of the regolith within permanently shadowed craters.


title: Moon

text: The next years saw a row of first missions to the Moon by a new group of states actively exploring the Moon.


title: Moon

text: Between 2004 and 2006 the first spacecraft by the European Space Agency (ESA) ("SMART-1") reached the Moon, recording the first detailed survey of chemical elements on the lunar surface.


title: Moon

text: The Chinese Lunar Exploration Program began with "Chang'e 1" between 2007 and 2009, obtaining a full image map of the Moon.


title: Moon

text: India reached the Moon in 2008 for the first time with its "Chandrayaan-1", creating a high-resolution chemical, mineralogical and photo-geological map of the lunar surface, and confirming the presence of water molecules in lunar soil.


title: Moon

text: The U.S. launched the "Lunar Reconnaissance Orbiter" (LRO) and the "LCROSS" impactor on 18 June 2009. "LCROSS" completed its mission by making a planned and widely observed impact in the crater Cabeus on 9 October 2009, whereas "LRO" is currently in operation, obtaining precise lunar altimetry and high-resolution imagery.


title: Moon

text: China continued its lunar program in 2010 with "Chang'e 2", mapping the surface at a higher resolution over an eight-month period, and in 2013 with "Chang'e 3", a lunar lander along with a lunar rover named "Yutu" (Chinese: 玉兔; literally "Jade Rabbit"). This was the first lunar rover mission since "Lunokhod 2" in 1973 and the first lunar soft landing since "Luna 24" in 1976.


title: Moon

text: Another Chinese rover mission, "Chang'e 4", achieved the first landing on the Moon's far side in early 2019.


title: Moon

text: In 2020, China carried out its first robotic sample return mission ("Chang'e 5"), bringing back 1,731 grams of lunar material to Earth.


title: Moon

text: With the signing of the U.S.-led Artemis Accords in 2020, the Artemis program aims to return in the astronauts to the Moon in the 2020s. The Accords have been joined by a growing number of countries. The introduction of the Artemis Accords has fueled a renewed discussion about the international framework and cooperation of lunar activity, building on the Moon Treaty and the ESA-led Moon Village concept. The U.S. developed plans for returning to the Moon beginning in 2004, which resulted in several programs. The Artemis program has advanced the farthest, and includes plans to send the first woman to the Moon as well as build an international lunar space station called Lunar Gateway.


title: Moon

text: Upcoming lunar missions include the Artemis program missions and Russia's first lunar mission, "Luna-Glob": an uncrewed lander with a set of seismometers, and an orbiter based on its failed Martian "Fobos-Grunt" mission.


title: Moon

text: In 2021, China announced a plan with Russia to develop and construct an International Lunar Research Station in the 2030s. In 2006, India and other countries expressed a hope to send people to the Moon by 2020.


title: Moon

text: Humans have been active around and on the Moon for more than half a century, having send a wide range of missions to the Moon, having stayed robotically and with people, leaving many traces and having set up temporary moonbases.


title: Moon

text: Lunar orbit has seen uninterrupted presence of orbiters since 2006, performing mainly lunar observation, but also providing relayed communication for missions on the lunar surface. Lunar orbits and orbits around Earth–Moon Lagrange points, have been gaining attention for being used to establish a near-lunar infrastructure, and with it enable increasing human activity in this so-called cislunar space as well as on the Moon's surface. Particularly missions at the far side of the Moon or the lunar north and south polar regions have been and will be in need for oebitees with special orbits, such as the Queqiao relay satellite or the planed first extraterrestrial space station, the Lunar Gateway.


title: Moon

text: While the Moon has the lowest planetary protection target-categorization, its degradation as a pristine body and scientific place has been discussed. If there is astronomy performed from the Moon, it will need to be free from any physical and radio pollution. While the Moon has no significant atmosphere, traffic and impacts on the Moon causes clouds of dust that can spread far and possibly contaminate the original state of the Moon and its special scientific content. Scholar Alice Gorman asserts that, although the Moon is inhospitable, it is not dead, and that sustainable human activity would require treating the Moon's ecology as a co-participant.


title: Moon

text: The so-called "Tardigrade affair" of the 2019 crashed Beresheet lander and its carrying of tardigrades has been discussed as an example for lacking measures and lacking international regulation for planetary protection.


title: Moon

text: Space debris beyond Earth around the Moon has been considered as a future challenge with increasing numbers of missions to the Moon, particularly as a danger for such missions. As such lunar waste management has been raised as an issue which future lunar missions, particularly on the surface, need to tackle.<ref name="NASA/ADS"></ref>


title: Moon

text: Beside the remains of human activity on the Moon, there have been some intended permanent installations like the "Moon Museum" art piece, Apollo 11 goodwill messages, six lunar plaques, the "Fallen Astronaut" memorial, and other artifacts.


title: Moon

text: Longterm missions continuing to be active are some orbiters such as the 2009-launched Lunar Reconnaissance Orbiter surveilling the Moon for future missions, as well as some Landers such as the 2013-launched Chang'e 3 with its Lunar Ultraviolet Telescope still operational.


title: Moon

text: Five retroreflectors have been installed on the Moon since the 1970s and since used for accurate measurements of the physical librations through laser ranging to the Moon.


title: Moon

text: There are several missions by different agencies and companies planned to establish a longterm human presence on the Moon, with the Lunar Gateway as the currently most advanced project as part of the Artemis program.


title: Moon

text: For many years, the Moon has been recognized as an excellent site for telescopes. It is relatively nearby; astronomical seeing is not a concern; certain craters near the poles are permanently dark and cold, and thus especially useful for infrared telescopes; and radio telescopes on the far side would be shielded from the radio chatter of Earth. The lunar soil, although it poses a problem for any moving parts of telescopes, can be mixed with carbon nanotubes and epoxies and employed in the construction of mirrors up to 50 meters in diameter. A lunar zenith telescope can be made cheaply with an ionic liquid.


title: Moon

text: In April 1972, the Apollo 16 mission recorded various astronomical photos and spectra in ultraviolet with the Far Ultraviolet Camera/Spectrograph.


title: Moon

text: The Moon has been also a sight of Earth observation, particularly culturally as in the imagery called Earthrise.


title: Moon

text: The only instances of humans living on the Moon have taken place in an Apollo Lunar Module for several days at a time (for example, during the Apollo 17 mission). One challenge to astronauts during their stay on the surface is that lunar dust sticks to their suits and is carried into their quarters. Astronauts could taste and smell the dust, calling it the "Apollo aroma". This fine lunar dust can cause health issues.


title: Moon

text: In 2019 at least one plant seed sprouted in an experiment on the Chang'e 4 lander. It was carried from Earth along with other small life in its "Lunar Micro Ecosystem".


title: Moon

text: Although "Luna" landers scattered pennants of the Soviet Union on the Moon, and U.S. flags were symbolically planted at their landing sites by the Apollo astronauts, no nation claims ownership of any part of the Moon's surface. Likewise no private ownership of parts of the Moon, or as a whole, is considered credible.


title: Moon

text: The 1967 Outer Space Treaty defines the Moon and all outer space as the "province of all mankind". It restricts the use of the Moon to peaceful purposes, explicitly banning military installations and weapons of mass destruction. A majority of countries are parties of this treaty.


title: Moon

text: The 1979 Moon Agreement was created to elaborate, and restrict the exploitation of the Moon's resources by any single nation, leaving it to a yet unspecified international regulatory regime. As of January 2020, it has been signed and ratified by 18 nations, none of which have human spaceflight capabilities.


title: Moon

text: Since 2020 countries have joined the U.S. in their Artemis Accords, which are challenging the treaty. The U.S. has furthermore emphasized in an presidential executive order ("Encouraging International Support for the Recovery and Use of Space Resources.") that "the United States does not view outer space as a 'global commons and calls the Moon Agreement "a failed attempt at constraining free enterprise."


title: Moon

text: With Australia signing and ratifying both the Moon Treaty in 1986 as well as the Artemis Accords in 2020, there has been a discussion if they can be harmonized. In this light an "Implementation Agreement" for the Moon Treaty has been advocated for, as a way to compensate for the shortcomings of the Moon Treaty and to harmonize it with other laws, allowing it to be more widely accepted.


title: Moon

text: In the face of such increasing commercial and national interest, particularly prospecting territories, U.S. lawmakers have introduced in late 2020 specific regulation for the conservation of historic landing sites and interest groups have argued for making such sites World Heritage Sites and zones of scientific value protected zones, all of which add to the legal availability and territorialization of the Moon.


title: Moon

text: In 2021 the "Declaration of the Rights of the Moon" was created by a group of "lawyers, space archaeologists and concerned citizens", drawing on precedents in the Rights of Nature movement and the concept of legal personality for non-human entities in space.


title: Moon

text: In light of future development on the Moon some international and multi-space agency organizations have been created:


title: Moon

text: Since pre-historic times people have taken note of the Moon's phases, its waxing and waning, and used it to keep record of time. Tally sticks, notched bones dating as far back as 20–30,000 years ago, are believed by some to mark the phases of the Moon. The counting of the days between the Moon's phases gave eventually rise to generalized time periods of the full lunar cycle as months, and possibly of its phases as weeks.


title: Moon

text: The words for the month in a range of different languages carry this relation between the period of the month and the Moon etymologically. The English "month" as well as "moon", and its cognates in other Indo-European languages (e.g. the Latin and Ancient Greek ("meis") or (mēn), meaning "month") stem from the Proto-Indo-European (PIE) root of "moon", *"méhnōt", derived from the PIE verbal root *"meh"-, "to measure", "indicat[ing] a functional conception of the Moon, i.e. marker of the month" (cf. the English words "measure" and "menstrual"). To give another example from a different language family, the Chinese language uses the same word () for "moon" as well as for "month", which furthermore can be found in the symbols for the word "week" ().


title: Moon

text: This lunar timekeeping gave rise to the historically dominant, but varied, lunisolar calendars. The 7th-century Islamic calendar is an example of a purely lunar calendar, where months are traditionally determined by the visual sighting of the hilal, or earliest crescent moon, over the horizon.


title: Moon

text: Of particular significance has been the occasion of full moon, highlighted and celebrated in a range of calenders and cultures. Around autumnal equinox, the Full Moon is called the Harvest Moon and is celebrated with festivities such as the Harvest Moon Festival of the Chinese Lunar Calendar, its second most important celebration after Chinese New Year.


title: Moon

text: Furthermore, association of time with the Moon can also be found in religion, such as the ancient Egyptian temporal and lunar deity Khonsu.


title: Moon

text: Since prehistoric and ancient times humans have depicted and interpreted the Moon, particularly for astrology and religion, as lunar deity.


title: Moon

text: For the representation of the Moon, especially its lunar phases, the crescent symbol (🌙) has been particularly used by many cultures. In writing systems such as Chinese the crescent has developed into the symbol , the word for Moon, and in ancient Egyptian it was the symbol , which is spelled like the ancient Egyptian lunar deity "Iah", meaning Moon.


title: Moon

text: Iconographically the crescent was used in Mesopotamia as the primary symbol of Nanna/Sîn, the ancient Sumerian lunar deity, who was the father of Innana/Ishtar, the goddess of the planet Venus (symbolized as the eight pointed Star of Ishtar), and Utu/Shamash, the god of the Sun (symbolized as a disc, optionally with eight rays), all three often depicted next to each other. Nanna was later known as Sîn, and was particularly associated with magic and sorcery.


title: Moon

text: The crescent was further used as an element of lunar deities wearing headgears or crowns in an arrangement reminiscent of horns, as in the case of the ancient Greek Selene or the ancient Egyptian Khonsu. Selene is associated with Artemis and paralleled by the Roman Luna, which both are occasionally depicted driving a chariot, like the Hindu lunar deity Chandra. The different or sharing aspects of deities within pantheons has been observed in many cultures, especially by later or contemporary culture, particularly forming triple deities. The Moon in Roman mythology for example has been associated with Juno and Diana, while Luna being identified as their byname and as part of a triplet ("diva triformis") with Diana and Proserpina, Hecate being identified as their binding manifestation as "trimorphos".


title: Moon

text: The star and crescent (☪) arrangement goes back to the Bronze Age, representing either the Sun and Moon, or the Moon and planet Venus, in combination. It came to represent the goddess Artemis or Hecate, and via the patronage of Hecate came to be used as a symbol of Byzantium, possibly influencing the development of the Ottoman flag, specifically the combination of the Turkish crescent with a star.


title: Moon

text: Since then the heraldric use of the star and crescent proliferated becoming a popular symbol for Islam (as the "hilal" of the Islamic calendar) and for a range of nations.


title: Moon

text: In Roman Catholic Marian veneration, the Virgin Mary (Queen of Heaven) has been depicted since the late middle ages on a crescent and adorned with stars. In Islam Muhammad is particularly attributed with the Moon through the so-called splitting of the Moon () miracle.


title: Moon

text: The contrast between the brighter highlands and the darker maria have been seen by different cultures forming abstract shapes, which are among others the Man in the Moon or the Moon Rabbit (e.g. the Chinese Tu'er Ye or in Indigenous American mythologies, as with the aspect of the Mayan Moon goddess).


title: Moon

text: The perception of the Moon in modern times has been informed by telescope enabled modern astronomy and later by spaceflight enabled actual human activity at the Moon, particularly the culturally impactful lunar landings. These new insights inspired cultural references, connecting romantic reflections about the Moon and speculative fiction such as science-fiction dealing with the Moon.


title: Moon

text: Contemporarily the Moon has been seen as a place for economic expansion into space, with missions prospecting for lunar resources. This has been accompanied with renewed public and critical reflection on humanity's cultural and legal relation to the celestial body, especially regarding colonialism, as in the 1970 poem "Whitey on the Moon". In this light the Moon's nature has been invoked, particularly for lunar conservation and as a common.


title: Moon

text: The lunar effect is a purported unproven correlation between specific stages of the roughly 29.5-day lunar cycle and behavior and physiological changes in living beings on Earth, including humans. The Moon has long been associated with insanity and irrationality; the words "lunacy" and "lunatic" are derived from the Latin name for the Moon, "Luna". Philosophers Aristotle and Pliny the Elder argued that the full moon induced insanity in susceptible individuals, believing that the brain, which is mostly water, must be affected by the Moon and its power over the tides, but the Moon's gravity is too slight to affect any single person. Even today, people who believe in a lunar effect claim that admissions to psychiatric hospitals, traffic accidents, homicides or suicides increase during a full moon, but dozens of studies invalidate these claims.


title: Borderline personality disorder

text: Borderline personality disorder (BPD), also known as emotionally unstable personality disorder (EUPD), is a personality disorder characterized by a long-term pattern of unstable interpersonal relationships, distorted sense of self, and strong emotional reactions. Those affected often engage in self-harm and other dangerous behaviors, often due to their difficulty with returning their emotional level to a healthy or normal baseline. They may also struggle with a feeling of emptiness, fear of abandonment, and detachment from reality. Symptoms of BPD may be triggered by events considered normal to others. BPD typically begins by early adulthood and occurs across a variety of situations. Substance use disorders, depression, and eating disorders are commonly associated with BPD. Some 8 to 10% of people affected by the disorder may die by suicide. The disorder is often stigmatized in both the media and the psychiatric field and as a result is often underdiagnosed.


title: Borderline personality disorder

text: The causes of BPD are unclear but seem to involve genetic, neurological, environmental, and social factors. It occurs about five times more often in a person who has an affected close relative. Adverse life events appear to also play a role. The underlying mechanism appears to involve the frontolimbic network of neurons. BPD is recognized by the American "Diagnostic and Statistical Manual of Mental Disorders" (DSM) as a personality disorder, along with nine other such disorders. The condition must be differentiated from an identity problem or substance use disorders, among other possibilities.


title: Borderline personality disorder

text: BPD is typically treated with psychotherapy, such as cognitive behavioral therapy (CBT) or dialectical behavior therapy (DBT). DBT may reduce the risk of suicide in the disorder. Therapy for BPD can occur one-on-one or in a group. While medications cannot cure BPD, they may be used to help with the associated symptoms. Quetiapine and SSRI antidepressants remain widely prescribed for the condition, though there is no evidence regarding the efficacy of the latter class of drugs. Severe cases of the disorder may require hospital care.


title: Borderline personality disorder

text: About 1.6% of people have BPD in a given year, with some estimates as high as 6%. Women are diagnosed about three times as often as men. The disorder appears to become less common among older people. Up to half of those with BPD improve over a ten-year period. Those affected typically use a high amount of healthcare resources. There is an ongoing debate about the naming of the disorder, especially the suitability of the word "borderline".


title: Borderline personality disorder

text: BPD is characterized by nine signs and symptoms. To be diagnosed, a person must meet at least five of the following:


title: Borderline personality disorder

text: Overall, the most distinguishing symptoms of BPD are pervasive patterns of instability in interpersonal relationships and self-image, alternating between extremes of idealization and devaluation of others, along with varying moods and difficulty regulating strong emotional reactions. Dangerous or impulsive behavior is also correlated with the disorder.


title: Borderline personality disorder

text: Other symptoms may include feeling unsure of one's identity, morals, and values; having paranoid thoughts when feeling stressed; depersonalization; and, in moderate to severe cases, stress-induced breaks with reality or psychotic episodes. Individuals with BPD often have comorbid conditions, such as depressive and bipolar disorders, substance use disorders, eating disorders, post-traumatic stress disorder, and attention-deficit/hyperactivity disorder.


title: Borderline personality disorder

text: People with BPD may feel emotions with greater ease and depth and for a longer time than others do. A core characteristic of BPD is affective instability, which generally manifests as unusually intense emotional responses to environmental triggers, with a slower return to a baseline emotional state. According to Marsha Linehan, the sensitivity, intensity, and duration with which people with BPD feel emotions have both positive and negative effects. People with BPD are often exceptionally enthusiastic, idealistic, joyful, and loving, but may feel overwhelmed by negative emotions (anxiety, depression, guilt/shame, worry, anger, etc.), experiencing intense grief instead of sadness, shame and humiliation instead of mild embarrassment, rage instead of annoyance, and panic instead of nervousness. Studies have shown that borderline patients experience chronic and significant emotional suffering and mental agony.


title: Borderline personality disorder

text: People with BPD are also especially sensitive to feelings of rejection, criticism, isolation, and perceived failure. Before learning other coping mechanisms, their efforts to manage or escape from their very negative emotions may lead to emotional isolation, self-injury or suicidal behavior. They are often aware of the intensity of their negative emotional reactions and, since they cannot regulate them, shut them down entirely since awareness would only cause further distress. This can be harmful since negative emotions alert people to the presence of a problematic situation and move them to address it.


title: Borderline personality disorder

text: While emotional dysregulation is a key feature of BPD, Fitzpatrick, et al. (2022) argue that the dysregulation itself may not be unique to BPD and be shared by other disorders, such as generalized anxiety disorder. However, their study did suggest that those with BPD may have a harder time disengaging from their negative emotions, using distraction to manage their emotions, and returning to a baseline emotional state.


title: Borderline personality disorder

text: While people with BPD feel euphoria (ephemeral or occasional intense joy), they are especially prone to dysphoria (a profound state of unease or dissatisfaction), depression, and/or feelings of mental and emotional distress. Zanarini et al. recognized four categories of dysphoria typical of this condition: extreme emotions, destructiveness or self-destructiveness, feeling fragmented or lacking identity, and feelings of victimization. Within these categories, a BPD diagnosis is strongly associated with a combination of three specific states: feeling betrayed, feeling out of control, and "feeling like hurting myself". Since there is great variety in the types of dysphoria people with BPD experience, the amplitude of the distress is a helpful indicator.


title: Borderline personality disorder

text: In addition to intense emotions, people with BPD experience emotional "lability" (changeability, or fluctuation). Although that term suggests rapid changes between depression and elation, mood swings in people with BPD more frequently involve anxiety, with fluctuations between anger and anxiety and between depression and anxiety.


title: Borderline personality disorder

text: People with BPD can be very sensitive to the way others treat them, by feeling intense joy and gratitude at perceived expressions of kindness, and intense sadness or anger at perceived criticism or hurtfulness. People with BPD often engage in idealization and devaluation of others, alternating between high positive regard for people and great disappointment in them. Their feelings about others often shift from admiration or love to anger or dislike after a disappointment, a threat of losing someone, or a perceived loss of esteem in the eyes of someone they value. This phenomenon is sometimes called splitting. Combined with mood disturbances, idealization and devaluation can undermine relationships with family, friends, and co-workers.


title: Borderline personality disorder

text: While strongly desiring intimacy, people with BPD tend toward insecure, avoidant or ambivalent, or fearfully preoccupied attachment patterns in relationships, and often view the world as dangerous and malevolent.


title: Borderline personality disorder

text: People with BPD are prone to feeling angry at members of their family and alienated from them. On their part, family members often feel angry and helpless at how their BPD family members relate to them. Parents of adults with BPD are often both over-involved and under-involved in family interactions. In romantic relationships, BPD is linked to increased levels of chronic stress and conflict, decreased satisfaction of romantic partners, domestic abuse, and unwanted pregnancy. However, these links may apply to personality disorders in general.


title: Borderline personality disorder

text: Impulsive behavior is common, including substance use disorders (e.g., alcohol use disorder), eating in excess, unprotected sex or indiscriminate sex with multiple partners, reckless spending, and reckless driving. Impulsive behavior may also include leaving jobs or relationships, running away, and self-injury. People with BPD might do this because it gives them the feeling of immediate relief from their emotional pain, but in the long term may feel shame and guilt over consequences of this behavior. A cycle often begins in which people with BPD feel emotional pain, engage in impulsive behavior to relieve that pain, feel shame and guilt over their actions, feel emotional pain from the shame and guilt, and then experience stronger urges to engage in impulsive behavior to relieve the new pain. As time goes on, impulsive behavior may become an automatic response to emotional pain.


title: Borderline personality disorder

text: Self-harming or suicidal behavior is one of the core diagnostic criteria in the DSM-5. Self-harm occurs in 50 to 80% of people with BPD. The most frequent method of self-harm is cutting. Bruising, burning, head banging or biting are also common with BPD. People with BPD may feel emotional relief after engaging in self-harm.


title: Borderline personality disorder

text: The estimation of lifetime risk of suicide among people with BPD varied—depending on method of investigation—between 3% and 10%. There is evidence that men diagnosed with BPD are approximately twice as likely to die by suicide as women diagnosed with BPD. There is also evidence that a considerable percentage of men who die by suicide may have undiagnosed BPD.


title: Borderline personality disorder

text: The reported reasons for self-harm differ from the reasons for suicide attempts. Nearly 70% of people with BPD self-harm without trying to end their lives. Reasons for self-harm include expressing anger, self-punishment, generating normal feelings (often in response to dissociation), and distracting oneself from emotional pain or difficult circumstances. In contrast, suicide attempts typically reflect a belief that others will be better off following the suicide. Suicide and self-harm are responses to feeling negative emotions. Sexual abuse can be a particular trigger for suicidal behavior in adolescents with BPD tendencies.


title: Borderline personality disorder

text: People with BPD tend to have trouble seeing their identity clearly. In particular, they tend to have difficulty knowing what they value, believe, prefer, and enjoy. They are often unsure about their long-term goals for relationships and jobs. This can cause people with BPD to feel "empty" and "lost". Self-image can also change rapidly from healthy to unhealthy. People with BPD may base their identity on others, leading to chameleon-like changes in identity.


title: Borderline personality disorder

text: The often intense emotions people with BPD experience may make it difficult for them to concentrate. They may also tend to dissociate, which can be thought of as an intense form of "zoning out". Others can sometimes tell when someone with BPD is dissociating because their facial or vocal expressions may become flat or expressionless, or they may appear distracted and "numb" to emotional stimuli.


title: Borderline personality disorder

text: Dissociation most often occurs in response to a painful event (or something that triggers the memory of a painful event). It involves the mind automatically redirecting attention away from the current event or situation or blocking it out entirely. This is done presumably to protect against - based on similar or related past experiences - what the mind perceives and forecasts as arousing intense negative emotions and unwanted behavioral impulses that the present emotive event might trigger. The mind's habit of suppressing and avoiding intensely painful emotions may provide some temporary feelings of relief, but dissociation can also lead to unhealthy coping mechanisms, while simultaneously causing the side-effect of blocking out or blunting positive emotions, thereby reducing the access of people with BPD to the valuable information those emotions provide: information that helps to guide effective, healthy decision-making in daily life.


title: Borderline personality disorder

text: Though BPD is primarily seen as a disorder of emotional regulation, psychotic symptoms are fairly common, with an estimated 21–54% prevalence in clinical BPD populations. These symptoms are sometimes referred to as "pseudo-psychotic" or "psychotic-like", terms that suggest a distinction from those seen in primary psychotic disorders. Recent research, however, has indicated that there is more similarity between pseudo-psychotic symptoms in BPD and "true" psychosis than originally thought. Some researchers critique the concept of pseudo-psychosis for, on top of weak construct validity, the implication that it is "not true" or "less severe", which could trivialize distress and serve as a barrier to diagnosis and treatment. Some researchers have suggested classifying these BPD symptoms as "true" psychosis, or even eliminating the distinction between pseudo-psychosis and true psychosis altogether.


title: Borderline personality disorder

text: The DSM-5 recognizes transient paranoia that worsens in response to stress as a symptom of BPD. Studies have documented both hallucinations and delusions in BPD patients who lack another diagnosis that would better account for those symptoms. Phenomenologically, research suggests that auditory verbal hallucinations found in patients with BPD cannot be reliably distinguished from those seen in schizophrenia. Some researchers suggest there may be a common etiology underlying hallucinations in BPD and those in other conditions like psychotic and affective disorders.


title: Borderline personality disorder

text: Many people with BPD are able to work if they find appropriate jobs and their condition is not too severe. People with BPD may be found to have a disability in the workplace if the condition is severe enough that the behaviors of sabotaging relationships, engaging in risky behaviors or intense anger prevent the person from functioning in their job role.


title: Borderline personality disorder

text: As is the case with other mental disorders, the causes of BPD are complex and not fully agreed upon. Evidence suggests that BPD and post-traumatic stress disorder (PTSD) may be related in some way. Most researchers agree that a history of childhood trauma can be a contributing factor, but less attention has historically been paid to investigating the causal roles played by congenital brain abnormalities, genetics, neurobiological factors, and environmental factors other than trauma.


title: Borderline personality disorder

text: The heritability of BPD is estimated to be between 37% to 69%. That is, 37% to 69% of the variability in liability underlying BPD in the population can be explained by genetic differences. Twin studies may overestimate the effect of genes on variability in personality disorders due to the complicating factor of a shared family environment. Even so, the researchers of one study concluded that personality disorders "seem to be more strongly influenced by genetic effects than almost any Axis I disorder [e.g., depression, eating disorders], and more than most broad personality dimensions". Moreover, the study found that BPD was estimated to be the third most-heritable personality disorder out of the 10 personality disorders reviewed. Twin, sibling, and other family studies indicate partial heritability for impulsive aggression, but studies of serotonin-related genes have suggested only modest contributions to behavior.


title: Borderline personality disorder

text: Families with twins in the Netherlands were participants of an ongoing study by Trull and colleagues, in which 711 pairs of siblings and 561 parents were examined to identify the location of genetic traits that influenced the development of BPD. Research collaborators found that genetic material on chromosome 9 was linked to BPD features. The researchers concluded that "genetic factors play a major role in individual differences of borderline personality disorder features". These same researchers had earlier concluded in a previous study that 42% of variation in BPD features was attributable to genetic influences and 58% was attributable to environmental influences. Genes under investigation include the 7-repeat polymorphism of the dopamine D4 receptor (DRD4) on chromosome 11, which has been linked to disorganized attachment, whilst the combined effect of the 7-repeat polymorphism and the 10/10 dopamine transporter (DAT) genotype has been linked to abnormalities in inhibitory control, both noted features of BPD. There is a possible connection to chromosome 5.


title: Borderline personality disorder

text: A number of neuroimaging studies in BPD have reported findings of reductions in regions of the brain involved in the regulation of stress responses and emotion, affecting the hippocampus, the orbitofrontal cortex, and the amygdala, amongst other areas. A smaller number of studies have used magnetic resonance spectroscopy to explore changes in the concentrations of neurometabolites in certain brain regions of BPD patients, looking specifically at neurometabolites such as N-acetylaspartate, creatine, glutamate-related compounds, and choline-containing compounds.


title: Borderline personality disorder

text: Some studies have identified increased gray matter in areas such as the bilateral supplementary motor area, dentate gyrus, and bilateral precuneus, which extends to the bilateral posterior cingulate cortex (PCC). The hippocampus tends to be smaller in people with BPD, as it is in people with post-traumatic stress disorder (PTSD). However, in BPD, unlike PTSD, the amygdala also tends to be smaller. This unusually strong activity may explain the unusual strength and longevity of fear, sadness, anger, and shame experienced by people with BPD, as well as their heightened sensitivity to displays of these emotions in others. Given its role in regulating emotional arousal, the relative inactivity of the prefrontal cortex might explain the difficulties people with BPD experience in regulating their emotions and responses to stress.


title: Borderline personality disorder

text: Borderline personality disorder has previously been strongly associated with the occurrence of childhood trauma or ACE (Adverse Childhood Experience). While many psychiatric diagnoses are believed to be associated with traumatic experiences occurring during critical periods of childhood, specific neurobiological factors have been identified within patients diagnosed with BPD. Dysregulations of the hypothalamic-pituitary-adrenal (HPA) axis and cortisol levels have been intensively studied in individuals who have experienced childhood traumas and have been formally diagnosed with BPD. The HPA axis functions to maintain homeostasis when the body is exposed to stressors but has been found to be dysregulated among individuals with a history of childhood abuse. When the body is exposed to stress, the hypothalamus, specifically the paraventricular nucleus (PVN) releases peptides arginine vasopressin (AVP) and corticotropin-releasing factor (CRF). When these peptides travel through the body, they stimulate corticotrophic cells, resulting in the release of adrenocorticotropic hormone (ACTH). ACTH binds to receptors in the adrenal cortex, which stimulates the release of cortisol. Intracellular glucocorticoid receptor subtypes of mineralocorticoid receptor (MR) and low-affinity type receptor (GR) have been found to mediate the effects of cortisol on different areas of the body. While MRs have high affinity for cortisol and are highly saturated in response to stress, GRs have low affinity for cortisol and bind cortisol at high concentrations when an individual is exposed to a stressor. There have also been associations identified with FKBP5 polymorphisms, rs4713902 and rs9470079 in individuals with BPD. For those with BPD who have experienced childhood trauma, rs3798347-T and rs10947563-A have been associated, specifically in individuals with both BPD diagnosis and a history of childhood physical abuse and emotional neglect.


title: Borderline personality disorder

text: The hypothalamic-pituitary-adrenal axis (HPA axis) regulates cortisol production, which is released in response to stress. Cortisol production tends to be elevated in people with BPD, indicating a hyperactive HPA axis in these individuals. This causes them to experience a greater biological stress response, which might explain their greater vulnerability to irritability. Since traumatic events can increase cortisol production and HPA axis activity, one possibility is that the prevalence of higher than average activity in the HPA axis of people with BPD may simply be a reflection of the higher than average prevalence of traumatic childhood and maturational events among people with BPD.


title: Borderline personality disorder

text: Individual differences in female's estrogen cycles may be related to the expression of BPD symptoms in female patients. A 2003 study found that women's BPD symptoms were predicted by changes in estrogen levels throughout their menstrual cycles, an effect that remained significant when the results were controlled for a general increase in negative affect.


title: Borderline personality disorder

text: There is a strong correlation between child abuse, especially child sexual abuse, and development of BPD. Many individuals with BPD report a history of abuse and neglect as young children, but causation is still debated. Patients with BPD have been found to be significantly more likely to report having been verbally, emotionally, physically, or sexually abused by caregivers of either sex. They also report a high incidence of incest and loss of caregivers in early childhood. Individuals with BPD were also likely to report having caregivers of both sexes deny the validity of their thoughts and feelings. Caregivers were also reported to have failed to provide needed protection and to have neglected their child's physical care. Parents of both sexes were typically reported to have withdrawn from the child emotionally and to have treated the child inconsistently. Additionally, women with BPD who reported a previous history of neglect by a female caregiver or abuse by a male caregiver were significantly more likely to have experienced sexual abuse by a non-caregiver.


title: Borderline personality disorder

text: It has been suggested that children who experience chronic early maltreatment and attachment difficulties may go on to develop borderline personality disorder. Writing in the psychoanalytic tradition, Otto Kernberg argues that a child's failure to achieve the developmental task of and failure to overcome splitting might increase the risk of developing a borderline personality.


title: Borderline personality disorder

text: The intensity and reactivity of a person's negative affectivity, or tendency to feel negative emotions, predicts BPD symptoms more strongly than does childhood sexual abuse. This finding, differences in brain structure (see Brain abnormalities), and the fact that some patients with BPD do not report a traumatic history suggest that BPD is distinct from the post-traumatic stress disorder which frequently accompanies it. Thus, researchers examine developmental causes in addition to childhood trauma.


title: Borderline personality disorder

text: Research published in January 2013 by Anthony Ruocco at the University of Toronto has highlighted two patterns of brain activity that may underlie the dysregulation of emotion indicated in this disorder: (1) increased activity in the brain circuits responsible for the experience of heightened emotional pain, coupled with (2) reduced activation of the brain circuits that normally regulate or suppress these generated painful emotions. These two neural networks are seen to be dysfunctionally operative in the limbic system, but the specific regions vary widely in individuals, which calls for the analysis of more neuroimaging studies.


title: Borderline personality disorder

text: Also (contrary to the results of earlier studies) those with BPD showed less activation in the amygdala in situations of increased negative emotionality than the control group. John Krystal, editor of the journal "Biological Psychiatry", wrote that these results "[added] to the impression that people with borderline personality disorder are 'set-up' by their brains to have stormy emotional lives, although not necessarily unhappy or unproductive lives". Their emotional instability has been found to correlate with differences in several brain regions.


title: Borderline personality disorder

text: While high rejection sensitivity is associated with stronger symptoms of borderline personality disorder, executive function appears to mediate the relationship between rejection sensitivity and BPD symptoms. That is, a group of cognitive processes that include planning, working memory, attention, and problem-solving might be the mechanism through which rejection sensitivity impacts BPD symptoms. A 2008 study found that the relationship between a person's rejection sensitivity and BPD symptoms was stronger when executive function was lower and that the relationship was weaker when executive function was higher. This suggests that high executive function might help protect people with high rejection sensitivity against symptoms of BPD. A 2012 study found that problems in working memory might contribute to greater impulsivity in people with BPD.


title: Borderline personality disorder

text: Family environment mediates the effect of child sexual abuse on the development of BPD. An unstable family environment predicts the development of the disorder, while a stable family environment predicts a lower risk. One possible explanation is that a stable environment buffers against its development.


title: Borderline personality disorder

text: Self-complexity, or considering one's self to have many different characteristics, may lessen the apparent discrepancy between an actual self and a desired self-image. Higher self-complexity may lead a person to desire more characteristics instead of better characteristics; if there is any belief that characteristics should have been acquired, these may be more likely to have been experienced as examples rather than considered as abstract qualities. The concept of a norm does not necessarily involve the description of the attributes that represent the norm: cognition of the norm may only involve the understanding of "being like", a concrete relation and not an attribute.


title: Borderline personality disorder

text: A 2005 study found that thought suppression, or conscious attempts to avoid thinking certain thoughts, mediates the relationship between emotional vulnerability and BPD symptoms. A later study found that the relationship between emotional vulnerability and BPD symptoms is not necessarily mediated by thought suppression. However, this study did find that thought suppression mediates the relationship between an invalidating environment and BPD symptoms.


title: Borderline personality disorder

text: Marsha Linehan's biosocial developmental theory of borderline personality disorder suggests that BPD emerges from the combination of an emotionally vulnerable child, and an invalidating environment. Emotional vulnerability may consist of biological, inherited factors that affect a child's temperament. Invalidating environments may include contexts where a child's emotions and needs are neglected, ridiculed, dismissed, or discouraged, or may include contexts of trauma and abuse.


title: Borderline personality disorder

text: Linehan's theory was modified by Sheila Crowell, who proposed that impulsivity also plays an important role in the development of BPD. Crowell found that children who are emotionally vulnerable and are exposed to invalidating environments are much more likely to develop BPD if they are also highly impulsive. Both theories describe an interplay between a child's inherited personality traits and their environment. For example, an emotionally sensitive or impulsive child may be difficult to parent, exacerbating the invalidating environment; conversely, invalidation can make an emotionally sensitive child more reactive and distressed.


title: Borderline personality disorder

text: Diagnosis of borderline personality disorder is based on a clinical assessment by a mental health professional. The best method is to present the criteria of the disorder to a person and to ask them if they feel that these characteristics accurately describe them. Actively involving people with BPD in determining their diagnosis can help them become more willing to accept it. Some clinicians prefer not to tell people with BPD what their diagnosis is, either from concern about the stigma attached to this condition or because BPD used to be considered untreatable; it is usually helpful for the person with BPD to know their diagnosis. This helps them know that others have had similar experiences and can point them toward effective treatments.


title: Borderline personality disorder

text: In general, the psychological evaluation includes asking the patient about the beginning and severity of symptoms, as well as other questions about how symptoms impact the patient's quality of life. Issues of particular note are suicidal ideations, experiences with self-harm, and thoughts about harming others. Diagnosis is based both on the person's report of their symptoms and on the clinician's own observations. Additional tests for BPD can include a physical exam and laboratory tests to rule out other possible triggers for symptoms, such as thyroid conditions or a substance use disorder. The ICD-10 manual refers to the disorder as "emotionally unstable personality disorder" and has similar diagnostic criteria. In the DSM-5, the name of the disorder remains the same as in the previous editions.


title: Borderline personality disorder

text: The "Diagnostic and Statistical Manual of Mental Disorders" fifth edition (DSM-5) has removed the multiaxial system. Consequently, all disorders, including personality disorders, are listed in Section II of the manual. A person must meet five of nine criteria to receive a diagnosis of borderline personality disorder. The DSM-5 defines the main features of the condition as a pervasive pattern of instability in interpersonal relationships, self-image, and affect, as well as markedly impulsive behavior. In addition, the DSM-5 proposes alternative diagnostic criteria for BPD in section III, "Alternative DSM-5 Model for Personality Disorders". These alternative criteria are based on trait research and include specifying at least four of seven maladaptive traits. According to Marsha Linehan, many mental health professionals find it challenging to diagnose BPD using the DSM criteria, since these criteria describe such a wide variety of behaviors. To address this issue, Linehan has grouped the symptoms of BPD under five main areas of dysregulation: emotions, behavior, interpersonal relationships, sense of self, and cognition.


title: Borderline personality disorder

text: The World Health Organization's ICD-10 defines a disorder that is conceptually similar to BPD, called "() Emotionally unstable personality disorder". Its two subtypes are described below.


title: Borderline personality disorder

text: At least three of the symptoms mentioned in "F60.30 Impulsive type" must be present [see above], with at least two of the following in addition:


title: Borderline personality disorder

text: The ICD-10 also describes some general criteria that define what is considered a personality disorder.


title: Borderline personality disorder

text: American psychologist Theodore Millon has proposed four subtypes of BPD. He suggests that an individual diagnosed with BPD may exhibit none, one, or multiple of the following:


title: Borderline personality disorder

text: People with BPD may be misdiagnosed for a variety of reasons. One reason for misdiagnosis is BPD has symptoms that coexist (comorbidity) with other disorders such as depression, post-traumatic stress disorder (PTSD), and bipolar disorder.


title: Borderline personality disorder

text: According to regression and factor analyses, the criteria for BPD do not even form a separate entity, and BPD is not distinguishable from negative affectivity. BPD diagnosis does not seem to add anything to other diagnoses. Rather, it seems unnecessary and even misleading. This is according to a study in "Personality Disorders", 2022.


title: Borderline personality disorder

text: Onset of symptoms typically occurs during adolescence or young adulthood, although symptoms suggestive of this disorder can sometimes be observed in children. Symptoms among adolescents that predict the development of BPD in adulthood may include problems with body-image, extreme sensitivity to rejection, behavioral problems, non-suicidal self-injury, attempts to find exclusive relationships, and severe shame. Many adolescents experience these symptoms without going on to develop BPD, but those who experience them are 9 times as likely as their peers to develop BPD. They are also more likely to develop other forms of long-term social disabilities.


title: Borderline personality disorder

text: BPD is recognised as a valid and stable diagnosis during adolescence. The diagnosis of BPD (also described as "personality disorder: borderline pattern qualifier") in adolescents is supported in recent updates to the international diagnostic and psychiatric classification tools including the DSM-5 and ICD-11. Early diagnosis of BPD has been recognised as instrumental to the early intervention and effective treatment for BPD in young people. Accordingly, national treatment guidelines recommend the diagnosis and treatment of BPD among adolescents in many countries including Australia, the United Kingdom, Spain, and Switzerland.


title: Borderline personality disorder

text: The diagnosis of BPD during adolescence has been controversial. Early clinical guidelines encouraged caution when diagnosing BPD during adolescence. Perceived barriers to the diagnosis of BPD during adolescence included concerns about the validity of a diagnosis in young people, the misdiagnosis of normal adolescent behaviour as symptoms of BPD, the stigmatising effect of a diagnosis for adolescents, and whether personality during adolescence was sufficiently stable for a valid diagnosis of BPD. Psychiatric research has since shown BPD to be a valid, stable and clinically useful diagnosis in adolescent populations. However, ongoing misconceptions about the diagnosis of BPD in adolescence remain prevalent among mental health professionals. Clinical reluctance to diagnose BPD is a key barrier to the provision of effective treatment in adolescent populations.


title: Borderline personality disorder

text: A BPD diagnosis in adolescence might predict that the disorder will continue into adulthood. Among individuals diagnosed with BPD during adolescence, there appears to be one group in which the disorder remains stable over time and another group in which the individuals move in and out of the diagnosis. Earlier diagnoses may be helpful in creating a more effective treatment plan for the adolescent. Family therapy is considered a helpful component of treatment for adolescents with BPD.


title: Borderline personality disorder

text: Lifetime comorbid (co-occurring) conditions are common in BPD. Compared to those diagnosed with other personality disorders, people with BPD showed a higher rate of also meeting criteria for:


title: Borderline personality disorder

text: A diagnosis of a personality disorder should not be made during an untreated mood episode/disorder, unless the lifetime history supports the presence of a personality disorder.


title: Borderline personality disorder

text: A 2008 study found that at some point in their lives, 75% of people with BPD meet criteria for mood disorders, especially major depression and bipolar I, and nearly 75% meet criteria for an anxiety disorder. Nearly 73% meet the criteria for a substance use disorder, and about 40% for PTSD. It is noteworthy that less than half of the participants with BPD in this study presented with PTSD, a prevalence similar to that reported in an earlier study. The finding that less than half of patients with BPD experience PTSD during their lives challenges the theory that BPD and PTSD are the same disorder.


title: Borderline personality disorder

text: There are marked sex differences in the types of comorbid conditions a person with BPD is likely to have—a higher percentage of males with BPD meet criteria for substance-use disorders, while a higher percentage of females with BPD meet criteria for PTSD and eating disorders. In one study, 38% of participants with BPD met the criteria for a diagnosis of ADHD. In another study, 6 of 41 participants (15%) met the criteria for an autism spectrum disorder (a subgroup that had significantly more frequent suicide attempts).


title: Borderline personality disorder

text: Regardless that it is an infradiagnosed disorder, a few studies have shown that the "lower expressions" of it might lead to wrong diagnoses. The many and shifting Axis I disorders in people with BPD can sometimes cause clinicians to miss the presence of the underlying personality disorder. However, since a complex pattern of Axis I diagnoses has been found to strongly predict the presence of BPD, clinicians can use the feature of a complex pattern of comorbidity as a clue that BPD might be present.


title: Borderline personality disorder

text: Many people with borderline personality disorder also have mood disorders, such as major depressive disorder or a bipolar disorder. Some characteristics of BPD are similar to those of mood disorders, which can complicate the diagnosis. It is especially common for people to be misdiagnosed with bipolar disorder when they have borderline personality disorder or vice versa. For someone with bipolar disorder, behavior suggestive of BPD might appear while experiencing an episode of major depression or mania, only to disappear once mood has stabilized. For this reason, it is ideal to wait until mood has stabilized before attempting to make a diagnosis.


title: Borderline personality disorder

text: At face value, the affective lability of BPD and the rapid mood cycling of bipolar disorders can seem very similar. It can be difficult even for experienced clinicians, if they are unfamiliar with BPD, to differentiate between the mood swings of these two conditions. However, there are some clear differences.


title: Borderline personality disorder

text: First, the mood swings of BPD and bipolar disorder tend to have different durations. In some people with bipolar disorder, episodes of depression or mania last for at least two weeks at a time, which is much longer than moods last in people with BPD. Even among those who experience bipolar disorder with more rapid mood shifts, their moods usually last for days, while the moods of people with BPD can change in minutes or hours. So while euphoria and impulsivity in someone with BPD might resemble a manic episode, the experience would be too brief to qualify as a manic episode.