Repeated low-dose LSD was safe but no better than placebo for adult ADHD
A 2025 clinical trial gave adults with ADHD repeated low doses of LSD — the kind of dose people take when 'microdosing' — to test whether it eased their symptoms better than a dummy pill.
Microdosing LSD has been talked about as a possible aid for ADHD, but until now it had not been put to a rigorous test. In this trial, 53 adults with a prior ADHD diagnosis and moderate-to-severe symptoms took either a low 20-microgram dose of LSD or a placebo (dummy pill) twice a week for six weeks — 12 doses in all. Neither the participants nor the people scoring their symptoms knew who received the real drug. After six weeks, both groups had improved, and the LSD group did no better than the placebo group: symptoms fell by about 7 points on LSD and about 9 points on placebo. LSD was physically safe and generally well tolerated, with no serious side effects. The authors concluded the low doses were safe but not more effective than placebo for ADHD.
In this 6-week, multicenter, double-blind, placebo-controlled, parallel-group phase 2A randomized clinical trial, 53 adults aged 18-65 with a prior ADHD diagnosis and moderate-to-severe symptoms (AISRS ≥26, CGI-S ≥4) were randomized to 20 μg LSD (n = 27) or placebo (n = 26) twice weekly for 6 weeks (12 doses total). The primary outcome was change in the Adult ADHD Investigator Symptom Rating Scale (AISRS) from baseline to week 6. The LSD group improved by a mean of -7.1 points (95% CI, -10.1 to -4.0) and the placebo group by -8.9 points (95% CI, -12.0 to -5.8), with no difference between groups. There were 124 adverse events in the LSD group versus 64 in the placebo group, with no serious adverse events and no deaths. The authors conclude that repeated low-dose LSD was safe in an outpatient setting but was not more efficacious than placebo in reducing ADHD symptoms.
The authors state several limitations. The trial was powered to detect a rather large effect, so very small effects may have been missed. Although described as multicenter, one site enrolled 95% of participants because of logistical problems. Expectancy — participants' beliefs about whether they received the active drug — was not systematically assessed. And only a single twice-weekly schedule at a fixed dose (relatively high for microdosing) was tested, leaving other doses and schedules unexamined. Design-inherent points: the sample was small (53 adults) and drawn from a general adult ADHD population, not a veteran or PTSD cohort, limiting direct generalization to veterans. Funding and conflicts warrant note — an author reported funding from Mind Medicine during the trial, and additional authors reported industry ties outside the submitted work.
In this randomized clinical trial, repeated low-dose LSD administration was safe in an outpatient setting but was not more efficacious than placebo in reducing ADHD symptoms (Mueller et al., 2025, JAMA Psychiatry).
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