Medical<unk>  is used to treat attention deficit hyperactivity disorder (ADHD), narcolepsy (a sleep disorder), and obesity, and is sometimes prescribed for its past medical indications, particularly for depression and chronic pain. Long-term<unk>  exposure at sufficiently high doses in some animal species is known to produce abnormal dopamine system development or nerve damage, but, in humans with ADHD, pharmaceutical<unk> s, at therapeutic dosages, appear to improve brain development and nerve growth. Reviews of magnetic resonance imaging (MRI) studies suggest that long-term treatment with<unk>  decreases abnormalities in brain structure and function found in subjects with ADHD, and improves function in several parts of the brain, such as the right caudate nucleus of the basal ganglia. Reviews of clinical stimulant research have established the safety and effectiveness of long-term continuous<unk>  use for the treatment of ADHD. Figure 3: Treatment benefit by treatment type and outcome group Randomized controlled trials of continuous stimulant therapy for the treatment of ADHD spanning 2 years have demonstrated treatment effectiveness and safety. Two reviews have indicated that long-term continuous stimulant therapy for ADHD is effective for reducing the core symptoms of ADHD (i.e., hyperactivity, inattention, and impulsivity), enhancing quality of life and academic achievement, and producing improvements in a large number of functional outcomes across 9 categories of outcomes related to academics, antisocial behavior, driving, non-medicinal drug use, obesity, occupation, self-esteem, service use (i.e., academic, occupational, health, financial, and legal services), and social function. One review highlighted a nine-month randomized controlled trial of<unk>  treatment for ADHD in children that found an average increase of 4.5 IQ points, continued increases in attention, and continued decreases in disruptive behaviors and hyperactivity. Another review indicated that, based upon the longest follow-up studies conducted to date, lifetime stimulant therapy that begins during childhood is continuously effective for controlling ADHD symptoms and reduces the risk of developing a substance use disorder as an adult. Current models of ADHD suggest that it is associated with functional impairments in some of the brain's neurotransmitter systems; these functional impairments involve impaired dopamine neurotransmission in the mesocorticolimbic projection and norepinephrine neurotransmission in the noradrenergic projections from the locus coeruleus to the prefrontal cortex. Psychostimulants like methylphenidate and<unk>  are effective in treating ADHD because they increase neurotransmitter activity in these systems. Approximately 80% of those who use these stimulants see improvements in ADHD symptoms. Children with ADHD who use stimulant medications generally have better relationships with peers and family members, perform better in school, are less distractible and impulsive, and have longer attention spans. The Cochrane reviews on the treatment of ADHD in children, adolescents, and adults with pharmaceutical<unk> s stated that short-term studies have demonstrated that these drugs decrease the severity of symptoms, but they have higher discontinuation rates than non-stimulant medications due to their adverse side effects. A Cochrane review on the treatment of ADHD in children with tic disorders such as Tourette syndrome indicated that stimulants in general do not make tics worse, but high doses of dextroamphetamine could exacerbate tics in some individuals. Enhancing performance Cognitive performance In 2015, a systematic review and a meta-analysis of high quality clinical trials found that, when used at low (therapeutic) doses,<unk>  produces modest yet unambiguous improvements in cognition, including working memory, long-term episodic memory, inhibitory control, and some aspects of attention, in normal healthy adults; these cognition-enhancing effects of<unk>  are known to be partially mediated through the indirect activation of both dopamine receptor D1 and adrenoceptor α2 in the prefrontal cortex. A systematic review from 2014 found that low doses of<unk>  also improve memory consolidation, in turn leading to improved recall of information. Therapeutic doses of<unk>  also enhance cortical network efficiency, an effect which mediates improvements in working memory in all individuals.<unk>  and other ADHD stimulants also improve task saliency (motivation to perform a task) and increase arousal (wakefulness), in turn promoting goal-directed behavior. Stimulants such as<unk>  can improve performance on difficult and boring tasks and are used by some students as a study and test-taking aid. Based upon studies of self-reported illicit stimulant use, of college students use diverted ADHD stimulants, which are primarily used for enhancement of academic performance rather than as recreational drugs. However, high<unk>  doses that are above the therapeutic range can interfere with working memory and other aspects of cognitive control. Physical performance<unk>  is used by some athletes for its psychological and athletic performance-enhancing effects, such as increased endurance and alertness; however, non-medical<unk>  use is prohibited at sporting events that are regulated by collegiate, national, and international anti-doping agencies. In healthy people at oral therapeutic doses,<unk>  has been shown to increase muscle strength, acceleration, athletic performance in anaerobic conditions, and endurance (i.e., it delays the onset of fatigue), while improving reaction time.<unk>  improves endurance and reaction time primarily through reuptake inhibition and release of dopamine in the central nervous system.<unk>  and other dopaminergic drugs also increase power output at fixed levels of perceived exertion by overriding a "safety switch", allowing the core temperature limit to increase in order to access a reserve capacity that is normally off-limits. At therapeutic doses, the adverse effects of<unk>  do not impede athletic performance; however, at much higher doses,<unk>  can induce effects that severely impair performance, such as rapid muscle breakdown and elevated body temperature.
Amphetamine
Benzphetamine
Methamphetamine
Benzocaine
Nicotine
3,4-Methylenedioxyamphetamine
Heroin
Cannabis 