At present, there are only a few drugs which have been shown to improve some aspect of cognition in medical reviews. Many more are in different stages of development. The most commonly used class of drug is stimulants.
These drugs are used primarily to treat people with cognitive or motor function difficulties attributable to such disorders as Alzheimer's disease, Parkinson's disease, Huntington's disease and ADHD. However, more widespread use is being recommended by some researchers. Many drugs are marketed heavily on the Internet as having a variety of human enhancement applications as well. Nevertheless, intense marketing may not correlate with efficacy; while scientific studies support the beneficial effects of some compounds, the marketing claims by manufacturers of over-the-counter products are not formally tested.
In academia, modafinil has been used to increase productivity, although its long-term effects have not been assessed in healthy individuals. Stimulants such as dimethylamylamine and methylphenidate are used on college campuses and by younger groups. One survey found that 7% of students had used stimulants for a cognitive edge, and on some campuses use in the past year is as high as 25%. The use of prescription stimulants is especially prevalent among students attending academically competitive colleges and students who are members of a fraternity or sorority.
Surveys suggest that 3–11% of American students and 0.7–4.5% of German students have used cognitive enhancers in their lifetime.
Several factors positively and negatively influence the use of drugs to increase cognitive performance. Among them are personal characteristics, drug characteristics, and characteristics of the social context.
The main concern with pharmaceutical drugs is adverse effects, and these concerns apply to cognitive-enhancing drugs as well. Cognitive enhancers are often taken for the long-term when little data is available. While certain racetam compounds are suspected to have nootropic qualities, few side-effects, and a wide therapeutic window (low overdose risk), other cognitive enhancers may be associated with a high incidence of adverse effects or a narrower therapeutic window (higher overdose risk). While addiction to stimulants is sometimes asserted to be a cause for concern, a very large body of research on the therapeutic use of the "more addictive" psychostimulants indicate that addiction is fairly rare in therapeutic doses.
In the United States, unapproved drugs or dietary supplements do not require safety or efficacy approval before being sold.
Certain stimulants will enhance cognition in the general population, but only when used at low (therapeutic) concentrations. Relatively high doses of stimulants will result in cognitive deficits.
Methylphenidate – a substituted phenethylamine that improves working memory and cognitive control. It also improves performance on tedious tasks that require a high degree of effort. At above optimal doses, methylphenidate has offtarget effects that can decrease learning by activating neurons not involved in the task at hand.
Xanthines – most notably, Caffeine – shown to increase alertness, performance, and in some studies, memory. Children and adults who consume low doses of caffeine showed increase alertness, yet a higher dose was needed to improve performance.
Nicotine – A meta-analysis of 41 double-blind, placebo-controlled studies concluded that nicotine or smoking had significant positive effects on aspects of fine motor abilities, alerting and orienting attention, and episodic and working memory.
Tianeptine – Tianeptine prevents stress-induced dendritic remodeling in various brain structures, enhances several metrics of cognition in animal models, and antagonizes alcohol's neurodegenerative effects.
Panax ginseng – Multiple RCTs in healthy volunteers have indicated increases in accuracy of memory, speed in performing attention tasks and improvement in performing difficult mental arithmetic tasks, as well as reduction in fatigue and improvement in mood.
Ginkgo Biloba – A meta-analysis of 29 RCTs stated "there is consistent evidence that chronic administration improves selective attention, some executive processes and long-term memory for verbal and non-verbal material."
St John's Wort – Anti-inflammatory, antibiotic, and neuroprotective antidepressant compound which has extremely low toxicity.
Isoflavones – A double-blind, placebo-controlled study showed improvement in spatial working memory after administration of isoflavones. One RCT showed soy isoflavone supplementation improved performance on 6 of 11 cognitive tests, including visual-spatial memory and construction, verbal fluency and speeded dexterity, but worse on two tests of executive function.
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Tianeptine prevents and reverses stress-induced glucocorticoid-mediated dendritic remodeling in CA3 pyramidal neurons in the hippocampus (40,41) and stress-induced increases in dendritic length and branching in the amygdala (50). Tianeptine blocks the dendritic remodeling caused by stress or glucocorticoids (41), blocks stress-induced impairments of spatial memory performance in radial and Y-maze (70,71) and antagonizes the deleterious effects of alcohol (72).
In a validated model of hippocampal-dependent memory impairment and synaptic plasticity changes by predator stress, acute tianeptine can prevent the deleterious effects of stress on spatial memory, an effect that does not depend on corticosterone levels (73). Tianeptine also facilitates focused attention behavior in the cat in response to its environment or towards a significant stimulus (74). It was shown to exert improving effects on learning as well as on working memory and on reference memory in rodents (72) and to exhibit vigilance-enhancing effects in rats (75) and monkeys (76)..."
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