What Are Nootropics? Definition, Types, Evidence and Safety

Key takeaways

• “Nootropic” is a loose label. A 2022 review notes that there is no uniform approach to categorizing these compounds. The word dates to 1972/1973, and the same review describes its original meaning as substances that primarily activate cognitive functions, especially where those functions are impaired.
• Evidence differs sharply by ingredient. Caffeine improved vigilance under sleep loss in a 2026 meta-analysis of randomized trials in military personnel and military-related populations. A 2026 meta-analysis found that L-theanine shows a robust short-term benefit on attention in healthy adults. A Cochrane review of older people with chronic cerebral disorders found no evidence that citicoline helps attention. A 2012 systematic review described the research on Rhodiola efficacy as contradictory.
• Several of the positive trials in the table enrolled older adults or people with a cognitive complaint, and a 2025 review states that in people without a cognitive deficit the potential for cognitive enhancement is limited.
• In the US, FDA does not approve dietary supplements before they are marketed. An FDA-hosted Justice Department release states that FDA has not approved racetam drugs, which it says include piracetam.
• Some ingredients carry their own risks; for example, a systematic review lists Ginkgo biloba among the supplements and foods that may increase bleeding risk in people taking warfarin. If you take any medication, talk to a clinician first.

What does “nootropic” mean?

The word was first used by Cornelius E. Giurgea in 1972/1973, according to a 2022 review. Giurgea published on the concept in French in 1972, and a paper titled “The ‘nootropic’ approach to the pharmacology of the integrative activity of the brain,” appeared in 1973.

The name comes from two Greek roots: nöos, “thinking,” and tropein, “to guide.”

Reviewers note that there is no uniform way to categorize these compounds: some separate “classical” nootropics from substances that enhance brain metabolism, others merge the two groups, and some avoid the word and speak of a “cognitive effect” instead. A 2025 narrative review says that clinicians who consider “nootropics” aim at treating cognition deficits in conditions such as Alzheimer’s disease, whereas the use of “smart drugs” refers to taking such compounds to improve mental performance in healthy individuals. This guide uses the word in that broader sense.

Giurgea’s original idea versus today’s usage

A 2022 review describes the original use of the term as covering substances that primarily activate cognitive functions such as memory and learning, especially where those functions are impaired. A 2016 review defines a cognition enhancer as “a pharmacological compound that enhances the mnemonic and cognitive function that can cross the blood-brain barrier,” and says it “does not have psychopharmacological activity such as sedation and has minimal or no adverse effects with low toxicity level.”

Modern use is broader and includes healthy people, such as students, who want to improve memory and cognitive function. Stimulants complicate the picture: one review describes guarana, an extract rich in caffeine, as exerting its effects primarily through its stimulant properties.

Three categories of nootropics

The label covers three quite different groups.

• Dietary-supplement ingredients: a 2022 review says the vast majority of nootropics are of natural origin, not subject to prescription, and usually easy to obtain as food supplements or herbal extracts. Examples: Lion’s Mane, Bacopa monnieri, L-theanine, citicoline and DHA.
• Synthetic compounds such as piracetam and structurally related racetams. A 1994 review of the literature through 1992 covered piracetam, oxiracetam, pramiracetam, aniracetam and related compounds, and concluded that no generally accepted mechanism of action had emerged. It found no affinity for glutamate receptors, among many others tested. Some clinical benefit has been shown in patients with mild to moderate dementia.
• Drugs used as “smart drugs.” A 2025 review says the most commonly used include methylphenidate, modafinil, amphetamines and psychedelics. Health risks from using them are a concern, especially without a prescription.

On natural versus synthetic, a 2022 review summarizes the trade-offs this way: natural nootropics usually have lower toxicity, which reduces the possibility of harm from an overdose, while synthetic compounds offer pharmaceutical purity and specificity of action but are usually active at lower doses, which raises overdose risk. The same review lists storage and possible falsification, and the difficulty of verifying authenticity, as problems for herbal products. See natural vs synthetic.

Nootropics versus stimulants and adaptogens

Caffeine exerts its effects by blocking adenosine receptors. In a review of its effects, low to moderate doses (about 40 mg to about 300 mg) improved alertness, vigilance, attention and reaction time, with less consistent effects on memory and higher-order executive function. Prescription stimulants are a different matter: FDA states that they are classified as Schedule II drugs under the Controlled Substances Act and associated with serious risks including misuse, addiction, overdose and diversion.

One 2022 review of nootropics deliberately left stimulants out, noting they have a primarily non-nootropic function. In practice the line blurs, because some supplement products pair a stimulant such as caffeine with other ingredients. The best-studied pairing is caffeine with L-theanine: a meta-analysis of 11 placebo-controlled studies of tea constituents (L-theanine and epigallocatechin gallate, alone or with caffeine) found moderate effect sizes favoring combined caffeine and L-theanine for alertness and attentional switching accuracy in the first 2 hours after a dose.

A 2021 study describes herbal adaptogens as plant medicines which have traditional associations with herbal tonics and promote homeostasis and non-specifically increase resistance to stress, but researchers note there is not yet enough clinical data for regulators in Europe or Australia to standardize the concept. Ashwagandha is described as an adaptogenic herb, and Rhodiola has been studied for performance because of its purported adaptogenic properties.

Is ashwagandha a nootropic? A 2022 review lists nootropic among the effects of withanolides, compounds found in ashwagandha (Withania somnifera), while a 2024 meta-analysis describes the herb as adaptogenic. A meta-analysis of nine randomized trials (558 patients) found significant effects on perceived stress, Hamilton Anxiety Scale scores and serum cortisol compared with placebo. One pilot trial tested memory directly in adults with mild cognitive impairment, where 50 adults took 300 mg twice daily or placebo for eight weeks.

What nootropic supplements are made of

The common ingredients fall into a few chemical families.

• Plant extracts. A 2022 review lists the active compounds by plant: bacosides and bacopasides in Bacopa, withanolides in ashwagandha, ginkgolides in Ginkgo, and rosavins and salidroside in Rhodiola.
• Mushrooms. Hericium erinaceus, also known as Lion’s Mane, is an edible mushroom, and a 2019 review reports that compounds extracted from its mycelia and fruiting bodies have been found to promote the expression of neurotrophic factors such as nerve growth factor.
• Amino acids and relatives. L-theanine is an amino acid derived from green tea, and, as a 2016 heat-stress trial describes it, tyrosine is a catecholamine precursor.
• Choline and phospholipids. Citicoline is a precursor essential for the synthesis of phosphatidylcholine, a cell membrane component, while phosphatidylserine in one trial was made from soybean lecithin by an enzymatic reaction with L-serine.

Form and dose matter. A 2022 review notes that higher doses of a herbal drug are needed to achieve the desired effect, which is why plant extracts are often used, and that giving too low a dose is a common mistake.

Do nootropics work? Evidence for 14 common ingredients

The honest answer depends on the ingredient, the outcome and who takes it. The table covers 14 ingredients we review on this site, with verdicts from our September 2026 evidence review of the claims made about each. “Supported” means published trials back the specific outcome named; “overstated” means common claims go further than the trials do; “contradicted” means a trial points the other way. A verdict applies to the outcome in the second column, not to the ingredient as a whole.

• Bacopa: in a 12-week trial of adults aged 40-70 with memory and attention complaints, 300 mg/day did not beat placebo on verbal learning, attention or working memory, although the Bacopa group showed greater reductions in self-reported stress reactivity than the placebo group.
• Lion’s Mane: in a 16-week trial in adults with mild cognitive impairment, scores rose over the 16 weeks and fell significantly four weeks after the tablets were stopped. In healthy young adults, a 41-person pilot of 1.8 g Lion’s Mane found faster Stroop performance 60 minutes after a single dose and a trend toward lower stress after 28 days that did not reach conventional significance.

What nootropics cannot do

• They are unlikely to make a healthy person “supernormal.” One review states that in people without a cognitive deficit the potential for enhancement is limited because baseline function is already near optimal. It adds that sustained high doses in healthy people may produce some desired effects but are often accompanied by increased risk of adverse outcomes.
• A 2022 review says these substances are more effective where cognitive functions are obviously impaired, and that few studies have been done in healthy young people.
• Caffeine improved vigilance during sleep loss in a meta-analysis, but a separate 2016 review found caffeine’s effects on memory and higher-order executive function less consistent.
• In February 2019 FDA concluded that products including Bacopa, L-theanine and Rhodiola, as marketed by one online seller with disease-treatment claims, were unapproved “new drugs.”
• In the children’s phosphatidylserine trial, several authors were employees of the company that commercializes the ingredient tested.

How long do nootropics take to work?

It depends on whether the effect is acute or cumulative. A 2022 review states that most nootropics do not have an immediate effect after a single dose, so long-term use is needed for the desired results. Timing varies:

• Acute: in the L-theanine meta-analysis, a single 200 mg dose taken 30-60 minutes before testing improved choice reaction time. A pilot study also found faster Stroop performance 60 minutes after a single dose of Lion’s Mane.
• Cumulative: other ingredients were tested for weeks or months, including 16 weeks for Lion’s Mane in mild cognitive impairment, 12 weeks for Bacopa, 60 days for ashwagandha, 6 months for phosphatidylserine and 24 weeks for DHA.
• Effects may not last: in the Lion’s Mane trial in mild cognitive impairment, scores fell significantly four weeks after the tablets were stopped.

See what to expect and how nootropics work.

Safety, side effects and the downsides

A 2022 review notes that nootropics tend to be well tolerated in people with cognitive impairment, with a low incidence of side effects that are usually mild, but that their long-term effects in healthy individuals are still unknown. “Natural” does not mean risk-free. Examples from the literature:

• Caffeine: FDA has cited 400 mg a day as an amount not generally associated with negative effects in most adults, but FDA notes there is wide variation in how sensitive people are to the effects of caffeine, and FDA says caffeine withdrawal is not considered dangerous but can be unpleasant.
• Bacopa: in a 12-week trial, adverse reactions were reported more often with Bacopa than with placebo, mainly digestive complaints and headaches.
• Omega-3 fatty acids: in a meta-analysis of seven large cardiovascular trials, marine omega-3 fatty-acid supplements were associated with a higher risk of atrial fibrillation, and the risk was greater in trials testing more than 1 g/day.
• Ashwagandha: reported cases include liver injury, and one case ended in liver transplantation.
• Ginkgo: a systematic review of warfarin interactions names Ginkgo biloba among the herbs and foods to be aware of for increased bleeding risk.
• Huperzine A inhibits acetylcholinesterase, the enzyme targeted by cholinesterase inhibitors, which are discussed as a treatment approach in Alzheimer’s disease. Ask your prescriber before combining it with such a drug.
• Rhodiola: laboratory work reported in a 2023 paper found that some constituents inhibited the MAO-A and MAO-B enzymes, and the paper notes that the clinical relevance of reported Rhodiola drug interactions is yet to be determined. If you take an MAO-inhibitor antidepressant, ask your prescriber first.

Are nootropics addictive? FDA states that prescription stimulants are classified as Schedule II drugs and associated with serious risks including misuse, addiction, overdose and diversion, and the DEA describes Schedule II substances as having a high potential for abuse which may lead to severe psychological or physical dependence. A 2025 review says that in individuals without cognitive impairment the potential for cognitive enhancement is limited and that they are more likely to experience negative effects, including sleep disturbances, mood instability, anxiety and reward-system dysfunctions/addiction behaviors, than a “supernormal” boost. For supplements, long-term effects in healthy people are still unknown, so treat “not addictive” claims with caution.

Are nootropics safe for teens? The evidence is thin. FDA notes that medical experts advise against energy drinks for children and teens because of their sugar and caffeine levels, according to the American Academy of Pediatrics, and that too much caffeine in children and teens can cause increased heart rate, heart palpitations, high blood pressure, anxiety, and sleep problems, digestive problems and dehydration. In the huperzine A trial in junior middle school students, the placebo group took capsules twice daily for 4 weeks. In the phosphatidylserine trial in children aged 8-12, participants received 100 mg or a placebo daily for 12 weeks. Trials this short cannot show long-term safety; ask a pediatrician first.

Pregnancy: In its section on nootropic treatment, the 2022 review states that nootropics are contraindicated in hypersensitivity, pregnancy and lactation. FDA recommends that anyone who is pregnant, trying to become pregnant or breastfeeding talk to a health care provider about whether they need to limit caffeine.

Legal and regulatory status in the US

US rules only here. Our page Are nootropics FDA approved? goes further. Rules differ elsewhere: a 2025 review notes that smart drugs may be available over the counter in some countries, on prescription, or from the internet, among other routes, so check your own country’s rules.

• Dietary supplements. Under the Dietary Supplement Health and Education Act (DSHEA), FDA does not have the authority to approve dietary supplements before they are marketed. Manufacturers and distributors of dietary supplements and dietary ingredients are responsible for evaluating the safety and labeling of their products before marketing, and FDA can act against an adulterated or misbranded supplement after it reaches the market.
• Claims. If a supplement label makes a structure/function claim, it must also carry the statement that FDA has not evaluated it and that the product is not intended to diagnose, treat, cure or prevent any disease. In a 2019 warning letter, FDA said the named products, which included Bacopa, L-theanine and Rhodiola, were “new drugs” because they were not generally recognized as safe and effective for the disease-related uses listed in the letter, and that new drugs may not be introduced into interstate commerce without prior FDA approval.
• Racetams. A Justice Department press release posted by FDA states that FDA has not approved drugs containing racetams for use in the United States, and lists piracetam, aniracetam and phenylpiracetam among racetam drugs. The FDA Q&A says the dietary supplement definition generally excludes ingredients that are approved as new drugs, unless the ingredient was previously marketed as a dietary supplement or as a food. In a February 2019 warning letter, FDA told one online seller that its adrafinil, aniracetam, noopept, oxiracetam, phenibut, phenylpiracetam, piracetam and pramiracetam products were not dietary supplements or conventional foods. A footnote to the letter says the seller’s piracetam product was not labeled as a dietary supplement, so the letter did not address whether piracetam can lawfully be marketed as one.
• Prescription stimulants. FDA states that they are classified as Schedule II drugs under the Controlled Substances Act, and the DEA lists amphetamine and methylphenidate among Schedule IIN stimulants. NIDA defines misuse to include taking someone else’s prescription, even for a legitimate medical complaint.
• Military. The Department of Defense’s prohibited-ingredients database states that Service Members are prohibited from using any substance it identifies as an ingredient in dietary supplements, and adds that controlled substances and drugs, including prescription, over-the-counter and unapproved drugs, are all prohibited for use in dietary supplements. The page we consulted was last updated on 3 September 2026.

How to start safely

1. Talk to a clinician first if you take prescription medication or have a medical condition. FDA notes that certain conditions, and some medications, can make people more sensitive to caffeine’s effects.
2. Start with one ingredient at a time so effects can be traced. See how to stack nootropics.
3. Check the extract type and dose per serving against the doses in the table.
4. Pick your outcome first and judge it over weeks, not days; focus vs memory maps ingredients to each.
5. In one 2019 warning letter, FDA said products promoted for disease uses were “new drugs” not generally recognized as safe and effective for those uses. Treat disease claims on a supplement as a red flag.
6. In one reported ashwagandha liver-injury case, a man developed nausea, pruritus (itching) and dark-colored urine after six months of use. If you develop symptoms like these, stop and get medical advice.