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Nootropics

Lion's Mane

A popular medicinal mushroom with intriguing preclinical biology but mixed, tiny, and product-specific human cognition studies.

Emerging
Evidence rating
Evidence review

What the evidence says

A 30-person Japanese trial in mild cognitive impairment reported better cognitive-scale scores during 16 weeks of 3 g per day of dried lion's mane, followed by decline after treatment stopped. The study was tiny, product specific, and included researchers from a mushroom company.[1]

A 41-person healthy-young-adult pilot found one faster Stroop result after a dose and only a trend toward lower stress after 28 days. A 2025 crossover study in 18 healthy adults found no significant benefit on its composite cognition or mood outcomes despite one better pegboard result.[2][3]

Another four-week study using 10 g per day found no cognitive benefit. A 2024 systematic review described human intervention results across mushrooms as mixed and called for larger, adequately powered trials.[4][5]

A small 49-week mild-Alzheimer trial of erinacine-A-enriched mycelia reported favorable measures, but several authors worked for the manufacturer and four participants stopped because of abdominal discomfort, nausea, or rash. It does not establish prevention or treatment of dementia.[6]

Dried fruiting body, concentrated fruiting-body extracts, and erinacine-enriched mycelia are chemically different. NIH LiverTox considers clinically apparent liver injury unlikely, but hypersensitivity and gastrointestinal effects have been reported and long-term standardized safety remains thin.[7][5]

Potential benefits

  • Small trials offer preliminary signals on selected cognitive or stress measures.[1][2]
  • The mixed human literature provides testable hypotheses for larger, product-specific trials.[5]

Side effects and cautions

  • Abdominal discomfort, nausea, and rash have led some trial participants to stop treatment.[6]
  • Mushroom allergy and uncertain product identity or standardization remain practical concerns.[7][5]
How we scored it

Evidence breakdown

Small trials report isolated cognitive or stress signals, while several controlled studies are null and formulations are not interchangeable.

Clinical relevanceLow

Most positive findings concern individual cognitive tests rather than daily function or disease prevention.

Study qualityLow

Human trials are small, vulnerable to multiple comparisons, and use different mushroom preparations.

Safety dataModerate

Short-term tolerability appears reasonable, but comprehensive prospective safety data are limited.

References

Full source list

  1. Improving effects of the mushroom Yamabushitake on mild cognitive impairment: a double-blind placebo-controlled clinical trial

    Phytotherapy Research · 2009

  2. The Acute and Chronic Effects of Lion's Mane Mushroom Supplementation on Cognitive Function, Stress and Mood in Young Adults

    Nutrients · 2023

  3. Acute effects of a standardised extract of Hericium erinaceus on cognition and mood in healthy younger adults

    Frontiers in Nutrition · 2025

  4. Four Weeks of Hericium erinaceus Supplementation Does Not Impact Markers of Metabolic Flexibility or Cognition

    Journal of Functional Morphology and Kinesiology · 2022

  5. A review of the effects of mushrooms on mood and neurocognitive health across the lifespan

    Neuroscience & Biobehavioral Reviews · 2024

  6. Prevention of Early Alzheimer's Disease by Erinacine A-Enriched Hericium erinaceus Mycelia

    Frontiers in Aging Neuroscience · 2020

  7. Lion's Mane

    LiverTox, National Institute of Diabetes and Digestive and Kidney Diseases · 2024