Users report anxiety, cognitive problems after taking lion’s mane supplements amid surge in sales

A growing number of people who took lion’s mane mushroom supplements say they experienced anxiety, panic attacks and prolonged cognitive problems after initial improvements in focus, raising safety questions as sales of the product soar.

Several users described a pattern of early cognitive benefits followed by troubling mental-health symptoms. Robyn Ramsay, 34, of Glasgow, said she began taking a 500 mg lion’s mane capsule daily while finishing a postgraduate diploma in counselling last April and noticed improved concentration. After doubling her dose to two capsules a day, still within recommended limits, she developed headaches within three weeks and had a panic attack about two weeks later. Ramsay said the symptoms persisted for months, included tinnitus and dissociation, and gradually eased only after she stopped the supplement and received medical treatment.

Another user, identified as Will Mason, said he took a 700 mg capsule daily in mid-2023 and initially felt more creative and focused. Within weeks he reported headaches, dizziness and a flu-like malaise, then more severe psychiatric symptoms including memory lapses and disorientation. Mason was hospitalized in Auckland for three days and has since reported prolonged fatigue, dissociation and difficulty performing everyday tasks. He and others called for tighter regulation of supplements.

The reports reflect a wider online community: a Reddit group of about 25,000 members has accumulated anecdotal accounts from users who say they experienced anxiety, panic attacks or dissociation after using lion’s mane. Market data show demand for the mushroom supplement has surged, with Nielsen reporting a 1,300 percent increase in UK sales over the past year.

Researchers and clinicians say lion’s mane (Hericium erinaceus), a white fungus with shaggy spines, contains compounds known as hericenones and erinacines that laboratory studies suggest may stimulate nerve growth factor and protect neurons. Small clinical trials have reported cognitive benefits in older adults. A 2009 randomized trial published in Phytotherapy Research found improved cognitive test performance after 16 weeks among 30 people over 50 with mild cognitive impairment. A 2019 randomized, placebo-controlled trial published in Biomedical Research International reported improved cognitive function in one measure among 31 healthy adults over 50 who took 3.2 g daily for 12 weeks. A more recent study in the journal Biomedicines reported that colorectal cancer patients given lion’s mane after surgery showed greater improvements in gut microbial diversity than a placebo group.

Catalina Fernandez de Ana Portela, a biologist at the University of Santiago de Compostela who has led clinical trials of mushrooms and runs a company that sells lion’s mane products, said the mushroom appears to benefit cognition and gut health by reducing inflammation, oxidative stress and by acting as a prebiotic. She said mushrooms are "bio-accumulators" that can absorb compounds from their growing medium and suggested contaminants in substrates could account for some adverse reactions.

Other experts urge caution. Edzard Ernst, formerly professor of complementary medicine at the University of Exeter, said preliminary evidence suggests potential benefits but warned of "numerous risks — ranging from allergic reactions to digestive problems, sleep disorders, panic attacks and interactions with prescribed drugs." He added that lion’s mane might worsen autoimmune conditions such as multiple sclerosis, lupus or rheumatoid arthritis. Nicholas Money, a biology professor at Miami University, said that if the mushroom affects the nervous system it could provoke anxiety in vulnerable individuals.

Clinicians and consumer-safety advocates point out that dietary supplements are regulated as food in many jurisdictions and do not undergo the same premarket testing for safety and efficacy as medicines. Supplements must meet food-safety requirements and labeling rules, but manufacturers are not required to provide clinical proof equivalent to that for pharmaceuticals. Martin Last, director general of the Health Foods Manufacturers’ Association, said the association promotes high production standards and compliance with Food Standards Agency guidance to ensure safe, quality products.

Users and clinicians also flagged possible interactions with prescription medications. Some people who experienced severe symptoms were treated with short courses of benzodiazepines or beta blockers to manage anxiety; others required psychiatric care. Several people who linked their symptoms to lion’s mane reported improvement after discontinuing the supplement, while others described long-lasting effects.

Researchers say larger, well-controlled clinical trials are needed to quantify both potential benefits and risks, to identify who might be at increased risk of adverse effects, and to determine whether cultivation methods or contaminants influence safety. In the meantime, health professionals recommend that consumers consult a doctor before taking new supplements, especially if they have pre-existing psychiatric or autoimmune conditions or are taking medication that could interact with botanical products.

Regulators, researchers and manufacturers continue to monitor safety signals as consumer interest in mushroom-based supplements grows. Until more complete evidence is available, experts advise caution and medical consultation for people considering lion’s mane, particularly those with underlying health vulnerabilities or who experience unexpected symptoms after starting the supplement.