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Nootropics (// noh-ə-TROP-iks), also referred to as smart drugs, memory enhancers, neuro enhancers, cognitive enhancers, and intelligence enhancers, are drugs, supplements, nutraceuticals, and functional foods that purportedly improve mental functions such as cognition, memory, intelligence, motivation, attention, and concentration. The word nootropic was coined in 1972 by the Romanian Dr. Corneliu E. Giurgea, derived from the Greek words νους nous, or "mind," and τρέπειν trepein meaning "to bend/turn". Nootropics are thought to work by altering the availability of the brain's supply of neurochemicals (neurotransmitters, enzymes, and hormones), by improving the brain's oxygen supply, or by stimulating nerve growth.
- 1 Nootropics vs. cognitive enhancers
- 2 Availability and prevalence
- 3 Hazards
- 4 Drugs
- 4.1 Racetams
- 4.2 Vitamins and supplements
- 4.3 Stimulants
- 4.4 Concentration and memory enhancement
- 4.5 Serotonergics
- 4.6 Dopaminergics
- 4.7 Sleep
- 4.8 Anti-depression, adaptogenic (anti-stress), and mood stabilization
- 4.9 Blood flow and metabolic function
- 4.10 Experimental histamine antagonists
- 4.11 Nerve growth stimulation and brain cell protection
- 4.12 Hormones
- 4.13 Unknown enhancement
- 4.14 Other nootropics
- 5 See also
- 6 References
- 7 External links
Nootropics vs. cognitive enhancers
||This section needs attention from an expert in Pharmacology. (February 2010)|
Cognitive enhancers are drugs, supplements, nutraceuticals, and functional foods that enhance attentional control and memory. Nootropics are cognitive enhancers that are neuroprotective or extremely nontoxic. Nootropics (such as Modafinil) are by definition cognitive enhancers, but a cognitive enhancer is not necessarily a nootropic.
Giurgea's nootropic criteria:
- Enhances learning and memory.
- Enhances learned behaviors under conditions which are known to disrupt them (e.g. hypoxia, sleep deprivation).
- Protects the brain from physical or chemical injury.
- Enhances the tonic cortical/subcortical control mechanisms
- Exhibits few side effects and extremely low toxicity, while lacking the pharmacology of typical psychotropic drugs (motor stimulation, sedation, etc.).
Since Giurgea's original criteria were first published, there has been little agreement as to what truly constitutes a nootropic compound. The most well defined criteria to date was established by Skondia in 1979. Skondia uses a metabolic approach, taking into account the pharmacological mode of action.
Skondia's nootropic criteria:
I. No direct vasoactivity
- A. No vasodilation
- B. No vasoconstriction
II. EEG activity: No change in basic rhythm
- A. Quantitative EEG: Increased power spectrum (beta 2 and alpha)
- B. Qualitative EEG: Decreased delta waves and cerebral suffering
III. Must pass blood-brain barrier
- A. Under normal conditions
- B. Under pathological conditions
IV. Must show metabolic activity in:
- A. Animal brain metabolism
- 1. Molecular
- 2. Physiopathological
- B. Human brain metabolism (clinical evaluation)
- 1. A-V differences
- a. Increased extraction quotients of O2
- b. Increased extraction quotients of glucose
- c. Reduced lactate pyruvate ratio
- 2. Regional cerebral metabolic rates (rCMR)
- a. Increased ICMR of O2
- b. Increased rCMR of glucose
- 3. Regional cerebral blood flow: Normalization
- 1. A-V differences
V. Minimal side effects
VI. Clinical trials must be conducted with several rating scales designed to objectify metabolic cerebral improvement.
Availability and prevalence
At present, there are several drugs on the market that improve memory, concentration, and planning, and reduce impulsive behavior. 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. These drugs have a variety of human enhancement applications as well, and are marketed heavily on the Internet. Nevertheless, intense marketing may not correlate with efficacy; while scientific studies support some of the claimed benefits, it is worth noting that not all of the claims from certain nootropics suppliers have been formally tested.
In academia a Nootropic called modafinil has been used to increase productivity, although its long-term effects have not been assessed in healthy individuals. Stimulants such as methylphenidate, a cognitive enhancer (which is not considered as a Nootropic according to the criteria above), are being used on college campuses, and by an increasingly younger group. 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/sorority.
Surveys suggest that 3-11% of American students and 0.7-4.5% of German students have used cognitive enhancers in their lifetime.
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.
Dr. Corneliu E. Giurgea originally coined the word nootropics for brain-enhancing drugs with very few side-effects. Racetams are sometimes cited as an example of a nootropic with few side-effects and a wide therapeutic window. In the United States, unapproved drugs or dietary supplements do not require safety or efficacy approval before being sold.
The word nootropic was coined upon discovery of the effects of piracetam, developed in the 1960s. Studies of the racetams have revealed that these structurally similar compounds often act via different mechanisms. Notable drugs include pramiracetam, oxiracetam, and aniracetam. Their mechanisms of action are not fully understood. Piracetam and aniracetam are known to act as positive allosteric modulators of AMPA receptors and appear to modulate cholinergic systems. Although aniracetam and nebracetam show affinity for muscarinic receptors, only nefiracetam shows it at the nanomolar range. Racetams have been called "pharmacologically safe" drugs.
Vitamins and supplements
- B Vitamins—may influence cognitive function through an effect on methylation and homocysteine levels, as excess homocysteine has been associated with cognitive impairment and the B vitamins work to reduce homocysteine. However, although epidemiological evidence shows an association, two studies did not find B vitamin supplementation improves cognitive function, and another that found an association was criticized. In 2008 a systematic review of trials found "little evidence of a beneficial impact" from supplements on cognitive function later in life. A randomized, placebo-controlled trial in 168 70 year olds with mild cognitive impairment showed that a mix of B vitamins slowed the rate of brain atrophy; the slowing was related to a decrease in homocysteine levels.
- Choline— Higher concurrent choline intake was related to better cognitive performance. It improves long-term memory in animal models.
- ω-3 fatty acids have been linked to the maintenance of brain function. Omega-3's provide DHA, important in the function and growth of nervous tissue. It is especially important during brain development. A study preformed in Norway demonstrated a potential link between Omega-3 consumption during pregnancy and child intelligence test scores. A cross-sectional population-based study of 1,613 subjects found an association between PUFA intake and decreased risk for impairment of cognitive function & cognitive speed. Another study showed that boys with lower levels of Omega-3 had more behavior issues, including ADHD.
- Isoflavones—may be related to cognitive function. A double-blind, placebo-controlled study showed improvement in spatial working memory after administration of an isoflavone combination containing daidzein, genistein & glycitein. In a randomized, double-blind, placebo-controlled study of older, non-demented men & women, soy isoflavone supplementation improved performance on 6 of 11 cognitive tests, including visual-spatial memory and construction, verbal fluency and speeded dexterity; unexpectedly, the placebo group performed better on 2 tests of executive function.
- Vitamin D—has positive effects on cardiovascular health and may have positive effects on cognitive function separately; the active form of Vitamin D seems to be involved in brain development and in adult brain function. In particular, metabolic pathways for Vitamin D in the hippocampus and cerebellum have been found. Epidemiological data show that higher Vitamin D levels (>20 ng/mL or 50nmol/L) are associated with better cognitive function, but do not seem to be associated with better memory performance. Vitamin D has also been shown to be necessary in the production of dopamine 
- Vitamin C— has been shown to help reduce brain injury and also reduce the amount of Cortisol in the body. High levels of Cortisol have been linked to Alzheimer's Disease.[medical citation needed]
- A 2007 survey of online databases for herbs used in traditional herbal medicine to treat cognitive decline – without any proof of safety or efficacy – found over 150 plant species, such as Ginkgo biloba and Epimedium which is commonly call 'Goat weed'.
Stimulants are often seen as smart drugs, but may be more accurately termed productivity enhancers. These typically improve concentration and a few areas of cognitive performance, but only while the drug is still in the blood at therapeutic concentrations. Some scientists recommend widespread use of stimulants such as methylphenidate and amphetamines by the general population to increase brain power.
- Dimethylamylamine—Non addictive stimulant. Once used in the treatment of ADHD and Burnout, but later discontinued.
- Atomoxetine—norepinephrine reuptake inhibitor; uncompetitive NMDA antagonist; clinically used in the treatment of ADHD
- Reboxetine—Norepinephrine reuptake inhibitor; approved in Europe for clinical depression but may also be used off-label to treat ADHD
- Synephrine—endogenous trace amine found in significant concentrations in the Bitter orange;agonist at α1 adrenergic receptors
- Arecoline—nicotinic agonist and partial agonist at muscarinic receptors M1-4
- Nicotine A meta-analysis of 41 double-blind, placebo-controlled studies concluded that nicotine or smoking had significant positive effects on fine motor, alerting attention-accuracy and response time (RT), orienting attention-RT, short-term episodic memory-accuracy, and working memory-RT.
- Eugeroics ("Wakefulness Enhancers")—unproven primary mechanisms but proven efficacy as a Nootropic
- Xanthines—reduces fatigue perception via adenosine receptor antagonism.
Concentration and memory enhancement
The nootropics in this section are purported or shown to enhance concentration or the recollection and formation of memories.
Cholinergics are substances that affect the neurotransmitter acetylcholine or the components of the nervous system that use acetylcholine. Acetylcholine is a facilitator of memory formation. Increasing the availability of this neurotransmitter in the brain may improve these functions. Cholinergic nootropics include acetylcholine precursors and cofactors, and acetylcholinesterase inhibitors:
- Acetylcholinesterase inhibitors
- Galantamine—also allosterically modulates certain nicotinic receptors to facilitate acetylcholine release
- Ipidacrine (Neiromidin) is a reversible cholinesterase inhibitor used in memory disorders of different origins.
- Lycoris radiata (Red Spider Lily)—natural source for galantamine
- Huperzine A—also shown to act as an NMDA antagonist and appears to increase nerve growth factor levels in rats
- Celastrus paniculatus
- cannabis Due to its AChE-inhibiting properties, Cannabis appears to increase acetylcholine levels and therefore studies suggest it as a treatment for Alzheimer's. Anxiolytic and analgesic found in cannabis. Neuroprotectant, possible Alzheimer's prevention and possible neurogenesis inducer. Possible neurotoxic effects of a notable constituent, THC, have been documented
- Reuptake inhibitors and enhancers
- α5IA—α5 inverse agonist. A number of α5IA analogues exist that, like α5IA, selectively and partially agonize some GABA receptor subtypes while inverse agonizing others, which may provide a nootropic effect without the associated anxiogenic effects of GABA inverse agonism.Template:Medial citation needed
- Suritozole—α5 partial inverse agonist
- Pantogam has a direct effect on the GABA-B receptor-channel complex.
Ligands and modulators of the AMPA receptor, an ionotropic glutamate receptor, are being researched for a myriad of conditions, from Alzheimer's to ADHD. Although there are many AMPAkines being researched, those mentioned here show signs of entering the market in the near future. Other notable drugs with AMPA-modulating activity include aniracetam and tianeptine.
- CX-717—pending FDA approval for memory-impairing illnesses and ADHD
- IDRA-21—believed to improve memory by significantly enhancing long-term potentiation but used only in animals; incredibly potent
- LY-503,430—under development for Parkinson's but showing increase in BDNF, specifically in areas of memory and higher cognitive skills
Cyclic adenosine monophosphate is a secondary messenger that may improve certain aspects of memory if increased. Common research tools for this purpose include PDE4 inhibitors, which prevents cAMP catabolism, and forskolin, a stimulator of adenylate cyclase.
- Forskolin—stimulates adenylate cyclase
- Propentofylline—nonselective phosphodiesterase inhibitor with some neuroenhancement
- Rolipram—PDE4 inhibitor, shows alertness enhancement, long term memory improvement and neuroprotection
- Mesembrine—PDE4-inhibitor with possible serotonergic activity
α2A receptors are concentrated heavily in the prefrontal cortex and the locus coeruleus, with the potential to improve attention abilities via modulating post-synaptic α2A receptors in the prefrontal cortex.
- Guanfacine is an α2A receptor agonist, FDA approved the treatment of ADHD. Guanfacine has been found to strengthen working memory, reduce distractibility, improve response inhibition, increase regional cerebral blood flow, reduce locomotor hyperactivity, and improve attentional control in animal models, as well as enhance memory function in humans. Another study found no effect on healthy male adult's executive functions and working memory, and small decrements on 2 tasks relating to the sedative effect of guanfacine.
- PRL-8-53 is a potent hypermnesic drug that significantly increases long term memory with a currently unknown mechanism of action involving cholinergic and dopaminergic activation.
Serotonin is a neurotransmitter with various effects on mood and possible effects on neurogenesis. Serotonergics are substances that affect the neurotransmitter serotonin or the components of the nervous system that use serotonin. Serotonergic nootropics include serotonin precursors and cofactors, and serotonin reuptake inhibitors:
- Reuptake inhibitors
- SSRIs—class of antidepressants that increase active serotonin levels by inhibiting reuptake, also shown to promote Neurogenesis in the hippocampus
- Sceletium tortuosum—active constituent mesembrine shown to act as an SSRI and PDE4 inhibitor. (Half-life unknown)
- Hypericum perforatum—inhibits reuptake of serotonin (as well as Norepinephrine, Dopamine, GABA and Glutamate) via activation of TRPC6
- MAO-A inhibitors
- 5-HT2A receptor agonists
- 2C-x—it has been reported that some these compounds causes nootropic, stimulant, or anti-anxiety effects at low doses. 2C-D, 2C-I, and 2C-C are examples. However, at hallucinogenic doses, these chemical compounds may be unpredictable. Research on these chemicals is sparse; they require further investigation.
- Tianeptine—atypical antidepressant with anxiolytic properties; a hypothesized mechanism of action revolves around modulation of NMDA and AMPA receptors, based on tianeptine's effect of promoting stress-associated impaired neuroplasticity; it increases the extracellular concentration of dopamine in the nucleus accumbens and modulates the D2 and D3 dopamine receptors, but this effect is modest and almost certainly indirect.
- Metabolic precursors—raise levels[medical citation needed]
- L-Phenylalanine—purported cognitive improvement
- L-Tyrosine (or N-Acetyl-L-Tyrosine, more bioavailable form)—purported cognitive improvement
- L-DOPA (L-3,4-dihydroxyphenylalanine)—precursor to catecholamines (dopamine); neurotoxic effects documented
- Biopterin—a vitamin (coenzyme) that is synthesized in the pineal gland & crucial to the biosynthesis of dopamine
- Pyridoxal-phosphate (or PLP, pyridoxal-5'-phosphate, P5P, active form of Vitamin B6)—cofactor for aromatic L-amino acid decarboxylase, the enzyme that decarboxylases L-DOPA, producing dopamine.
- Reuptake inhibitors—stabilize/improve levels[medical citation needed]
- MAO-B inhibitors—prevent some catabolism of dopamine and β-PEA
- Dopamine agonists
- Mucuna pruriens (Velvet Bean)—natural source of L-DOPA
- Modafinil—purported dopaminergic activity that exhibits the criteria of a Nootropic
- Citicoline (INN) (aka: cytidine diphosphate-choline (CDP-Choline) & cytidine 5'-diphosphocholine)—studies suggest CDP-choline supplements partially prevent the loss of dopamine D2 receptors in aged mice, and that CDP-choline supplementation ameliorates memory impairment caused by environmental conditions (in rats). Preliminary research has found that citicoline may have potential in the treatment of attention deficit-hyperactivity disorder.
Sleep is known to be important in memory consolidation, mood, anxiety, appetite, and numerous other physiological processes. Drugs that improve sleep may therefore have an indirect nootropic effect.
- Melatonin—antioxidant. Exogenous melatonin protects against substantia nigra cell loss in ovariectomized rats. May normalize circadian rhythms in humans
- Agomelatine— MT1 receptor agonist and 5-HT2C neutral antagonist
Anti-depression, adaptogenic (anti-stress), and mood stabilization
Stress (specifically elevated levels of circulating corticosteroids) has been associated with the cognitive deficits seen in human aging. Many studies show that stress and fatigue negatively impact cognitive functioning in young adults. Some level of stress in the learning environment may aid the ability to focus and retain information. However, stress levels, especially high, sustained or traumatic stressors, hinder declarative memory, spatial reasoning, learning, attention and working memory. Fatigue is also a stressor that impedes attention, processing, retrieval, working memory and short term memory. The effects of stress on cognitive performance seem to be controlled by the sympatho-adrenal system and the hypothalamic-hypophysial-adrenal axis.
It is reasoned that counteracting and preventing depression and stress management may be an effective nootropic strategy. Proper nutrition, adequate sleep, and mechanisms for coping with stress, such as meditation, have been shown to improve learning and cognitive functioning both in the short and long term.
The substances below may not have been mentioned earlier on the page:
- Beta blockers—evidence from controlled trials spanning 25 years supports the claim that beta-blockers are effective for reducing anxiety, likely through peripheral blockade of beta-receptors; most data comes from studies of generalized anxiety and acute stress.
- Theanine—relaxation; found in green tea; increases nicotinic acetylcholine and reduces nicotinic dopamine
- Lemon Balm—displays adaptogen properties; in rats it has been shown to possess GABA transaminase inhibitor activity and in homogenates of human cerebral cortical cell membranes possesses activity at acetylcholine receptors. In a randomized, double-blind, placebo-controlled study of 18 healthy volunteers, 600 mg of 'Melissa officinalis' extract attenuated volunteers' response to a laboratory-induced stress test 1 hour after administration; 300 mg significantly improved speed of mathematical processing 1 hour after administration.
- Passion Flower—possible MAOI and neurotransmitter reuptake activity
- Rhodiola Rosea—adaptogen; possible MAOI activity
- St John's Wort—herbal supplement approved (in Europe) to treat mild depression. Method of action is unproven but exhibits effects similar to both MAOIs and SSRIs. There is evidence that it may decrease the effectiveness of methylphenidate treatment.
- Ginseng (including Siberian ginseng)—adaptogenic effects shown
- Sutherlandia frutescens—possible anti-inflammatory, reducing pain from those illnesses
- Kava—anxiolytic herb
- Grape seed extract—has shown some efficacy in reducing bodily stress
- Adafenoxate—possible anxiolytic effect
- Phenibut GABA receptor agonist excerting anxiolytic effects
- Picamilon GABA prodrug which excerts anxiolytic effects by releasing GABA and niacin in the CNS.
- Valerian—possible anxiolytic effect through agonism at GABA-A receptors
- Butea frondosa—possible anxiolytic effect
- Gotu Kola—adaptogen and anxiolytic
- Foti[disambiguation needed]—adaptogen; possible MAOI activity
- Panax ginseng—Multiple randomized, placebo-controlled studies in healthy volunteers have been performed, results include 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.
- Many Chinese herbs such as Polygala tenuifolia, Acorus gramineus and Huperzia serrata.
- Bacopa monnieri
- Tulsi (Ocimum sanctum, sweet holy basil)
- IAP(5-APDI) Lifts mood and promotes a peaceful mindset. Anti-anxiety.
- 2-methyl-2-butanol Anti-anxiety that lifts mood and increases sociability. Although it doesn't have the side effects or toxic metabolites that ethanol has, frequent use may cause dependence.
Blood flow and metabolic function
Brain function is dependent on many basic processes such as the usage of ATP, removal of waste, and intake of new materials. Improving blood flow or altering these processes can benefit brain function. The list below contains only vasodilators that have shown at least probable mental enhancement.
- Mildronate may improve the ability of learning and memory, as the drug changes the expression of hippocampal proteins related to synaptic plasticity
- Blessed Thistle—increases blood circulation, improving memory
- Coenzyme q-10—antioxidant; increases oxygen usage by mitochondria
- Creatine—protects ATP during transport
- Lipoic acid—improves oxygen usage and antioxidant recycling, possibly improving memory
- Pyritinol—Drug similar to B vitamin Pyridoxine
- Picamilon—GABA activity and blood flow improver
- Ginkgo biloba—vasodilator. Acts as an NRI. A double-blind, placebo-controlled trial in young healthy females showed an improvement in short-term memory performance 1 hour after administration of a 600 mg dose. An analysis of 29 placebo-controlled RCTs showed that "there is consistent evidence that chronic administration improves selective attention, some executive processes and long-term memory for verbal and non-verbal material." A double-blind, placebo-controlled study in 20 young healthy volunteers showed a dose-dependent improvement in speed-of-attention following administration of 240 mg and 360 mg of Ginkgo extract, effects were measured 2.5h after administration and persisted at least until 6h; various other time- and dose-specific changes (some positive, some negative) in other areas were observed.
- Vinpocetine— is reported to have cerebral blood-flow enhancing and neuroprotective effects, and is used as a drug in Eastern Europe for the treatment of cerebrovascular disorders and age-related memory impairment. Also shown to inhibit voltage-sensitive Na+ channels—however, through a similar mechanism to reserpine, Vinpocetine may temporarily deplete the monoamines serotonin, dopamine and norepinephrine by inhibiting VMAT, thus preventing them from reaching the synapse. Vinpocetine may therefore induce or exacerbate depressive symptoms as an adverse effect. However, this effect tends to be reversible upon cessation of Vinpocetine administration, with full remission typically occurring within 3–4 weeks. Vinpocetine has been identified as a potent anti-inflammatory agent that might have a potential role in the treatment of Parkinson's disease and Alzheimer's disease.
- Vincamine—increases blood circulation (vasodilator) and metabolism in the brain; related to vinpocetine; used in sustained release.
- Nicergoline—an ergot derivative used to treat senile dementia and other disorders with vascular origins; it has been found to increase mental agility and enhance clarity and perception; it decreases vascular resistance and increases arterial blood flow in the brain, improving the utilization of oxygen and glucose by brain cells; it has been used for more than three decades for the treatment of cognitive, affective, and behavioral disorders of older people.
Experimental histamine antagonists
The H3-receptor decreases neurotransmitter release: histamine, acetylcholine, norepinephrine, serotonin. Thus, H3-receptor-antagonists increases cognition, vigilance, and wakefulness.
- Ciproxifan—produces wakefulness and attentiveness in animal studies, and produced cognitive enhancing effects without prominent stimulant effects at relatively low levels of receptor occupancy, and pronounced wakefulness at higher doses.
- A-349,821—It has nootropic effects in animal studies.
- ABT-239 – strong H3 receptor inverse agonist that is more active than ciproxifan, but its investigation into human use was dropped after it was discovered to cause QT prolongation in subjects
Nerve growth stimulation and brain cell protection
Nerves are necessary to the foundation of brain communication and their degeneracy, underperformance, or lacking can have disastrous results on brain functions. Antioxidants may prevent oxidative stress and cell death, therefore exerting a neuroprotective effect.
- Idebenone—antioxidant
- Glutathione—chief antioxidant
- Sesamol—antioxidant 
- Acetylcarnitine (Acetyl-L-Carnitine Arginate or Hydrochloride)
- Inositol—implicated in memory function, deficit linked to some psychiatric illnesses—has been shown particularly efficacious in OCD patients
- Anticonvulsants—inhibit seizure related brain malfunction if a person has seizures
- Phosphatidylserine—possible membrane stabilizer
- Lion's Mane Mushroom—Stimulated myelination in an in vitro experiment and stimulated nerve growth factor in an in vitro experiment with human astrocytoma cells. Also improved cognitive ability, in a double-blind, parallel-group, placebo-controlled trial.
- SAM-e (S-Adenosyl methionine)—crucial for cellular regeneration (fuels DNA methylation), also involved with the biosynthesis of dopamine & serotonin
- Acetylcysteine (L-cysteine)—precursor to antioxidant glutathione
- Uncaria tomentosa (Cat's Claw)—in an in vitro experiment with rats, it inhibited formation of brain beta amyloid deposits, which have been associated with Alzheimer's disease.
- (Cannabidiol and Δ9-tetrahydrocannabinol)—Cannabidiol (nonpsychoactive) and Δ9-tetrahydrocannabinol (psychotropic) antioxidant.
These are hormones that have activity not necessarily attributable to another specific chemical interaction, but have shown effectiveness. Only specific nootropic effects are stated.
- Vasopressin—memory hormone that improves both memory encoding and recall. Desmopressin (1-desamino-8-D-arginine vasopressin, DDAVP) was given to 17 children with attention & learning disorders daily for 10 days in a placebo-controlled, randomized, double-blind study; memory & learning were improved compared with placebo; the same study failed to find similar benefits after administration of a single dose.
- Pregnenolone—increases neurogenesis[medical citation needed]
- Orexin or Hypocretin—significant wakefulness promoter
- DHEA—precursor to estrogen and testosterone
Other agents purported to have nootropic effects but do not (yet) have attributable mechanisms or clinically significant effects (but may upon refinement of administration) are listed below.
Nootropics with proven or purported benefits:
- Polygala tenuifolia (Yuan Zhi)— A randomized, double-blind, placebo-controlled, parallel-group study of the extract of dried roots of Polygala tenuifolia in healthy adults produced memory-enhancing effects. A similar trial with elderly humans also found significant cognitive improvement.
- Bacopa monniera (Brahmi) — Shown to possess adaptogenic properties and enhance memory and concentration. Folk use in Ayurvedic medicine purports "enhancement of curiosity"; Brahmi rasayana has been shown to improve learning and memory in mice
- Clitoria ternatea (Shankhpushpi) — In traditional Ayurvedic medicine, it has been used for centuries as a memory enhancer, nootropic, antistress, anxiolytic, antidepressant, anticonvulsant, tranquilizing and sedative agent.
- Fipexide—drug for Dementia
- Piperic acid—allegedly a mild serotonergic, nootropic, antistress, anxiolytic, and allegedly has mild to moderate memory enhancing effects.
- Gerovital H3—famous alleged anti-aging mixture, most effects disproven but some mind enhancement shown
- Sulbutiamine—fat soluble vitamin B1 derivative—caused mice to perform better on operant conditioning tests and object recognition tests
- Royal Jelly—Increases brain cell growth and diversity, only demonstrated in-vitro, improbable in-vivo (it has been reported to stimulate the growth of glial cells and neural stem cells in the brain.)
- Curcumin—significant in-vitro activity, but in-vivo activity limited by low bioavailability unless accompanied by ingestion of piperine
- Cognitive science
- Eidetic memory
- Human enhancement
- Long-term potentiation
- Memory and aging
- Psychedelics in problem-solving experiment
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- List of Nootropic drugs at Erowid
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