How common is microdosing in California, and what do the studies actually show?

How many Californians microdose?

Nobody has measured it for the whole state. Microdosing is the term for taking "a fraction of a full dose, often on a schedule," in RAND's wording, usually of psilocybin, LSD or MDMA.¹ This page covers psychedelics, not cannabis, which one UC San Diego survey also counted.²

The closest California figure comes from USC researchers who surveyed 2,396 young adults aged 18 to 22 in a Los Angeles cohort between October 2018 and November 2019. Of those, 12% had heard of microdosing and 3% (74 people) had tried it, and psilocybin was the drug they microdosed most often (70%). Because about 18% of self-described microdosers reported far larger amounts, the authors say 3% may be an overestimate.³

For hallucinogens in general, SAMHSA's state estimates for 2023 to 2024 put past-year use at 4.45% of Californians 12 and older, about 1.5 million people, against 3.36% nationally. That figure counts any hallucinogen use, not microdosing alone.⁴

The team behind this site also runs an online shop, and if you want the shop's own take, there's a microdosing guide from My Mushroom Dispensary. This page sticks to what researchers measured. Psilocybin is illegal under California and federal law, and ordering it online is illegal everywhere in the US.⁵⁶

What do national surveys find?

These surveys asked different questions of different samples, so their numbers shouldn't be added or swapped.

RAND's survey put past-year psilocybin use alone at 4.26%, about 11 million adults.¹ The federal survey's 3.1% covers all hallucinogens and uses different methods, so the gap between the two isn't a trend. Definitions are loose as well: the UC San Diego team notes that "no standardized definition or validated measure for microdosing currently exists."²

How much did interest in microdosing rise?

A UC San Diego study in JAMA Health Forum tracked Google searches for "microdosing," "micro dosing," "microdose" and "micro dose." US search rates were flat through 2014, then rose 13.4-fold from 2015 to 2023, from 7.9 to 105.6 per 10 million searches. That came to 3.0 million US searches in 2023.⁸

By 2023, rates were highest in Oregon (202.5 per 10 million) and in Colorado and Washington (159.6 each). Local psychedelic decriminalization was associated with 22.4 more searches per 10 million, and recreational cannabis laws with 40.9 more. The paper gives no California figure, and searches measure curiosity, not use.⁸

What happened when researchers used placebos?

The real test is whether people do better on the drug than on an identical dummy when nobody knows which they got. "Breaking blind" means participants work out which one they took, letting expectations leak into the results (our reporter's glossary defines more terms like it).

A systematic review and meta-analysis published in August 2026 covered 24 studies with 3,681 healthy adults, 6 of which fed its pooled analyses. Randomized trials showed "no clear evidence" of lower depression, anxiety or stress, improvements seen in some studies "were not significantly different from placebo," and adverse events were similar on drug and control. The authors call the trial evidence inconclusive and want larger trials.¹³

Why do app-based studies look more positive?

The best-known positive results come from people who chose to microdose and logged it in a phone app. A 2021 study compared 4,050 self-selected microdosers (85% of them using psilocybin) with 4,653 people who didn't microdose. Among people reporting mental-health concerns, microdosers had lower depression, anxiety and stress scores. The design was cross-sectional, and the authors call for "rigorous longitudinal designs."¹⁴

Read the conflict-of-interest statement too. The lead author had research funding from Quantified Citizen, the company whose app collected the data; its CEO and chief technology officer were co-authors; and co-author Paul Stamets, a minority investor in the company, is an applicant on pending patents combining psilocybin mushrooms, lion's mane and niacin.¹⁴ The August 2026 meta-analysis concluded that improvements in observational studies were "likely influenced by expectancy or lifestyle factors."¹³

What risks have researchers flagged?

Heart valves (theoretical). Researchers have proposed valve disease as a possible risk because psilocin and related drugs activate the serotonin 5-HT2B receptor. A 2023 review found "no animal or clinical studies appropriately designed to evaluate" that risk for psilocybin and other psychedelics, and concluded it is "a potential risk with chronic psychedelic microdosing, but further studies are necessary." No study has shown this harm in people who microdose psilocybin, and none has ruled it out.¹⁵

Lithium. In an analysis of online experience reports, 47% of 62 reports of a classic psychedelic taken with lithium involved seizures and 39% involved medical attention; none of 34 lamotrigine reports involved seizures. These are uncontrolled self-reports, but the authors say psychedelic use "may pose a significant seizure risk for patients on lithium."¹⁶

Antidepressants. In a retrospective online survey, the probability of weaker-than-expected effects was 0.47 for people taking SSRIs and 0.55 for SNRIs, against 0.29 for bupropion, and the dampening may last "as long as 3 months" after stopping. That's self-report, not a controlled trial.¹⁷ For what lab tests have found in mushroom candy sold in smoke shops, see our comparison of mushroom gummies by compound.

In an emergency, call 911. For a mental-health crisis, call or text 988; in San Diego County, the Access and Crisis Line is 888-724-7240.¹⁸ Poison Control (1-800-222-1222) is free, confidential and open 24 hours.¹⁹ Fireside Project's psychedelic peer support line, 62-FIRESIDE (623-473-7433), takes calls and texts from 11 a.m. to 11 p.m. Pacific; it isn't a suicide hotline.²⁰ Our guide to getting help during a bad trip covers what to do next.

What does California law say about microdosing?

There's no small-amount exception. Psilocybin and psilocyn are Schedule I in California under Health and Safety Code 11054(d)(18) and (19), which reach "any material, compound, mixture, or preparation, which contains any quantity" of them.⁵ They're also Schedule I under federal law, 21 USC 812(c), a category Congress defined as having "no currently accepted medical use in treatment in the United States."⁶

Our California psilocybin penalties guide sets out the charges statute by statute. The guide to legal psilocybin options for Californians maps the routes that do exist, including the regulated programs in Oregon and Colorado, and the San Diego psychedelic clinical trials directory lists local studies.