A diagram of the human body showing some of the diseases caused by<unk> <unk>  is one of the leading causes of preventable death globally and is the cause of 15% of all deaths. In the United States, about 500,000 deaths per year are attributed to<unk> -related diseases and a recent study estimated that as much as 1/3 of China's male population will have significantly shortened life-spans due to<unk> . Male and female smokers lose an average of 13.2 and 14.5 years of life, respectively. At least half of all lifelong smokers die earlier as a result of<unk> . The risk of dying from lung cancer before age 85 is 22.1% for a male smoker and 11.9% for a female current smoker, in the absence of competing causes of death. The corresponding estimates for lifelong nonsmokers are a 1.1% probability of dying from lung cancer before age 85 for a man of European descent, and a 0.8% probability for a woman.<unk>  just one cigarette a day results in a risk of coronary heart disease that is halfway between that of a heavy smoker and a non-smoker. The non-linear dose–response relationship may be explained by<unk> 's effect on platelet aggregation. Among the diseases that can be caused by<unk>  are vascular stenosis, lung cancer, heart attacks and chronic obstructive pulmonary disease.<unk>  during pregnancy may cause ADHD to a fetus.<unk>  is a risk factor strongly associated with periodontitis and tooth loss. The effects of<unk>  on periodontal tissues depend on the number of cigarettes smoked daily and the duration of the habit. A study showed that smokers had 2.7 times and former smokers 2.3 times greater probabilities to have established periodontal disease than non‐smokers, independent of age, sex and plaque index, however, the effect of tobacco on periodontal tissues seems to be more pronounced in men than in women. Studies have found that smokers had greater odds for more severe dental bone loss compared to non‐smokers , also, people who smoke and drink alcohol heavily have much higher risk of developing oral cancer (mouth and lip) compared with people who do neither.<unk>  can also cause milanosis in the mouth.<unk>  has been also associated with oral conditions including dental caries, dental implant failures, premalignant lesions, and cancer.<unk>  can affect the immune-inflammatory processes which may increase the susceptibility to infections; it can alter the oral mycobiota and facilitate colonization of the oral cavity with fungi and pathogenic molds. Many governments are trying to deter people from<unk>  with anti-smoking campaigns in mass media stressing the harmful long-term effects of<unk> . Passive<unk> , or secondhand<unk> , which affects people in the immediate vicinity of smokers, is a major reason for the enforcement of<unk>  bans. These are laws enforced to stop individuals from<unk>  in indoor public places, such as bars, pubs and restaurants, thus reducing nonsmokers’ exposure to secondhand smoke. A common concern among legislators is to discourage<unk>  among minors and many states have passed laws against selling tobacco products to underage customers (establishing a<unk>  age). Many developing countries have not adopted anti-smoking policies, leading some to call for anti-smoking campaigns and further education to explain the negative effects of ETS (Environmental Tobacco Smoke) in developing countries. Tobacco advertising is also sometimes regulated to make<unk>  less appealing. Despite the many bans, European countries still hold 18 of the top 20 spots, and according to the ERC, a market research company, the heaviest smokers are from Greece, averaging 3,000 cigarettes per person in 2007. Rates of<unk>  have leveled off or declined in the developed world but continue to rise in developing countries.<unk>  rates in the United States have dropped by half from 1965 to 2006, falling from 42% to 20.8% in adults. The effects of addiction on society vary considerably between different substances that can be smoked and the indirect social problems that they cause, in great part because of the differences in legislation and the enforcement of narcotics legislation around the world. Though nicotine is a highly addictive drug, its effects on cognition are not as intense or noticeable as other drugs such as cocaine, amphetamines or any of the opiates (including heroin and morphine).<unk>  is a risk factor in Alzheimer's disease. While<unk>  more than 15 cigarettes per day has been shown to worsen the symptoms of Crohn's disease,<unk>  has been shown to actually lower the prevalence of ulcerative colitis. Smokers are 30-40% more likely to develop type 2 diabetes than non-smokers, and the risk increases with the number of cigarettes smoked. File:Share-deaths-smoking.Share of deaths from<unk> , 2017 File:Death-rate-smoking.The number of deaths attributed to<unk>  per 100,000 people in 2017 Physiology A graph that shows the efficiency of<unk>  as a way to absorb nicotine compared to other forms of intake Inhaling the vaporized gas form of substances into the lungs is a quick and very effective way of delivering drugs into the bloodstream (as the gas diffuses directly into the pulmonary vein, then into the heart and from there to the brain) and affects the user within less than a second of the first inhalation. The lungs consist of several million tiny bulbs called alveoli that altogether have an area of over 70 m2 (about the area of a tennis court). This can be used to administer useful medical as well as recreational drugs such as aerosols, consisting of tiny droplets of a medication, or as gas produced by burning plant material with a psychoactive substance or pure forms of the substance itself. Not all drugs can be smoked, for example the sulphate derivative that is most commonly inhaled through the nose, though purer free base forms of substances can, but often require considerable skill in administering the drug properly. The method is also somewhat inefficient since not all of the smoke will be inhaled. The inhaled substances trigger chemical reactions in nerve endings in the brain due to being similar to naturally occurring substances such as endorphins and dopamine, which are associated with sensations of pleasure. The result is what is usually referred to as a "high" that ranges between the mild stimulus caused by nicotine to the intense euphoria caused by heroin, cocaine and methamphetamines. Inhaling smoke into the lungs, no matter the substance, has adverse effects on one's health. The incomplete combustion produced by burning plant material, like tobacco or cannabis, produces carbon monoxide, which impairs the ability of blood to carry oxygen when inhaled into the lungs. There are several other toxic compounds in tobacco that constitute serious health hazards to long-term smokers from a whole range of causes; vascular abnormalities such as stenosis, lung cancer, heart attacks, strokes, impotence, low birth weight of infants born by<unk>  mothers. 8% of long-term smokers develop the characteristic set of facial changes known to doctors as smoker's face. Tobacco smoke is a complex mixture of over 5,000 identified chemicals, of which 98 are known to have specific toxicological properties. The most important chemicals causing cancer are those that produce DNA damage since such damage appears to be the primary underlying cause of cancer. Cunningham et al. combined the microgram weight of the compound in the smoke of one cigarette with the known genotoxic effect per microgram to identify the most carcinogenic compounds in cigarette smoke. The seven most important carcinogens in tobacco smoke are shown in the table, along with DNA alterations they cause. +The most genotoxic cancer causing chemicals in cigarette smoke Compound Micrograms per cigarette Effect on DNA Ref. Acrolein 122.4 Reacts with deoxyguanine and forms DNA crosslinks, DNA-protein crosslinks and DNA adducts Formaldehyde 60.5 DNA-protein crosslinks causing chromosome deletions and re-arrangements Acrylonitrile 29.3 Oxidative stress causing increased 8-oxo-2'-deoxyguanosine 1,3-butadiene 105.0 Global loss of DNA methylation (an epigenetic effect) as well as DNA adducts Acetaldehyde 1448.0 Reacts with deoxyguanine to form DNA adducts Ethylene oxide 7.0 Hydroxyethyl DNA adducts with adenine and guanine Isoprene 952.0 Single and double strand breaks in DNA Psychology Sigmund Freud, whose doctor assisted with his suicide because of oral cancer caused by<unk>  Most tobacco smokers begin during adolescence or early adulthood.<unk>  has elements of risk-taking and rebellion, which often appeal to young people. The presence of high-status models and peers may also encourage<unk> . Because teenagers are influenced more by their peers than by adults, attempts by parents, schools, and health professionals at preventing people from trying cigarettes are not always successful. Smokers often report that cigarettes help relieve feelings of stress. However, the stress levels of adult smokers are slightly higher than those of nonsmokers. Adolescent smokers report increasing levels of stress as they develop regular patterns of<unk> , and<unk>  cessation leads to reduced stress. Far from acting as an aid for mood control, nicotine dependency seems to exacerbate stress. This is confirmed in the daily mood patterns described by smokers, with normal moods during<unk>  and worsening moods between cigarettes. Thus, the apparent relaxant effect of<unk>  only reflects the reversal of the tension and
Smoking
Sedentary lifestyle
Obesity
Passive smoking
Family history 
Vegetarianism
Psychiatric history
Body mass index