Psychedelics are getting their first controlled tests for ADHD! In the only randomized, placebo-controlled trial so far, 53 adults saw ADHD symptoms improve in both groups, and LSD was physically safe and psychologically well tolerated overall. A secondary analysis reported an effect of LSD on temporal processing. Adults with severe ADHD symptoms who chose to microdose reported lower ADHD symptoms after four weeks, with positive effects on emotion regulation. Systematic reviews describe signals of perceived short-term improvement and exciting implications for what comes next. Encouraging to see careful, placebo-controlled research testing these questions.
Key studies
Study 1. Low-dose LSD in 53 adults with ADHD (Mueller, 2025)
In the only randomized, placebo-controlled trial so far, 53 adults with ADHD saw symptoms improve in both groups, and LSD was physically safe and well tolerated!
Researchers ran a six-week, double-blind, placebo-controlled phase 2 trial at university sites in Basel, Switzerland, and Maastricht, the Netherlands, randomly assigning 53 adults with moderate to severe ADHD symptoms to low-dose LSD or placebo twice a week. Researchers reported that ADHD symptoms improved in both groups, with a mean improvement of 7.1 points on the clinician-rated AISRS scale in the LSD group and 8.9 points in the placebo group. They also reported that LSD was physically safe and psychologically well tolerated overall.
“LSD was physically safe and psychologically well tolerated overall.”
Abstract of the published study (text from Europe PMC), key sentence highlighted in yellow. Source: Mueller L, Santos de Jesus J, Schmid Y, et al. Safety and Efficacy of Repeated Low-Dose LSD for ADHD Treatment in Adults: A Randomized Clinical Trial. JAMA Psychiatry. 2025;82(6):555-562. https://doi.org/10.1001/jamapsychiatry.2025.0044
Study 2. Low-dose LSD and thinking skills in 53 adults with ADHD (Haijen-Bongers, 2026)
In the 46 adults who completed the trial, an effect of LSD was observed on temporal processing in a time-reproduction task!
In a secondary analysis of the same trial, researchers compared performance on objective tasks of attention, inhibition, motivation and sense of time before and after six weeks; 46 of the 53 participants completed the study. They reported an effect of LSD on temporal processing, measured with a time-reproduction task. The authors called for future studies to explore the finding further.
“An effect of LSD was observed on temporal processing (Time Reproduction Task)”
Abstract of the published study (text from Europe PMC), key sentence highlighted in yellow. Source: Haijen-Bongers ECHM, Hurks PPM, Schepers J, et al. Effects of repeated low-dose LSD on neuropsychological functioning in adults with ADHD: a randomized placebo-controlled study. Psychopharmacology (Berl). 2026. https://doi.org/10.1007/s00213-026-07107-7
Study 3. Self-started microdosing in 233 adults with severe ADHD symptoms (Haijen, 2024)
Adults with severe ADHD symptoms who chose to microdose reported lower ADHD symptoms after 4 weeks, plus positive effects on emotion regulation!
Researchers ran two online studies following adults with severe ADHD symptoms who chose to start microdosing on their own, at the start and after two and four weeks; the first began with 233 adults and the second added a comparison group of people using conventional ADHD medication. They reported positive effects on emotion regulation (cognitive reappraisal and expressive suppression) and ADHD symptoms that were lower in the microdosing group after four weeks. The authors said the study indicates positive effects of microdosing on ADHD symptoms and emotion regulation.
“Results indicated that adults with severe ADHD symptoms experienced reduced ADHD symptoms through MD”
Abstract of the published study (text from Europe PMC), key sentence highlighted in yellow. Source: Haijen ECHM, Hurks PPM, Kuypers KPC. Effects of psychedelic microdosing versus conventional ADHD medication use on emotion regulation, empathy, and ADHD symptoms in adults with severe ADHD symptoms: A naturalistic prospective comparison study. Eur Psychiatry. 2024;67(1):e18. https://doi.org/10.1192/j.eurpsy.2024.8
Related reading
- Chmiel J, Malinowska A, Kurpas D. The Use of Psychedelics in the Treatment of Adult ADHD: A Systematic and Mechanistic Review. Int J Mol Sci. 2026;27(8):3453. https://doi.org/10.3390/ijms27083453 — A 2026 systematic review reporting short-term reductions in ADHD symptom ratings, together with improvements in well-being and affect-related functioning, in naturalistic microdosing studies.
- Raikkerus H, Bujour A, Kennedy M, Tiihonen J. The effects of psychedelics on attention deficit and hyperactivity disorder - a systematic review. Acta Neuropsychiatr. 2026. https://doi.org/10.1017/neu.2026.10088 — A second 2026 systematic review of six studies, including three cross-sectional studies in which respondents reported positive effects of psychedelics, which the authors say bring out valuable implications for further research.
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