Controlled trial finds microdosing LSD ineffective for adult ADHD

A recent placebo-controlled study reveals that low-dose LSD does not outperform placebo in treating adult ADHD, highlighting the need for more rigorous research and caution against unsubstantiated claims circulating on social media.

The best controlled test yet of psychedelic microdosing for adult ADHD found that low-dose LSD did not beat placebo, and a later review says that remains the defining result in a field heavy on enthusiasm but light on hard evidence. Researchers examining the available literature found only five prospective or experimental studies in adults and concluded that psychedelics cannot currently be presented as an evidence-based treatment for ADHD. (jamanetwork.com)

The pivotal trial, published online by JAMA Psychiatry on 19 March 2025, was a six-week, multicentre, double-blind, placebo-controlled phase 2A study carried out in Basel and Maastricht between 17 December 2021 and 4 December 2023. Fifty-three adults aged 18 to 65 with moderate to severe ADHD were randomised to receive 20 micrograms of LSD or placebo twice weekly, for 12 supervised doses in total. On the main clinician-rated scale, symptoms fell by 7.1 points in the LSD group and 8.9 points in the placebo group, leaving no statistically significant advantage for the drug. MedicalXpress reported that the work was conducted by scientists from Switzerland and the Netherlands. (jamanetwork.com)

That matters because the trial also showed how strong expectation effects can be in psychedelic research. JAMA reported that 37 of 46 participants, or 80%, guessed after the last dose that they had been given LSD. Speaking to PsyPost, Basel investigator Matthias Liechti said: “In a well-designed study, low dose LSD (microdosing) is not more effective than placebo in patients with ADHD.” The study did suggest that repeated low-dose LSD could be given safely in an outpatient setting, with mostly mild adverse reactions including headache, nausea, fatigue, insomnia and visual alterations. PsyPost added that two people left the LSD arm because of uncomfortable effects, but there were no serious medical events or psychiatric complications. (jamanetwork.com)

The new review argues that this single negative trial has to be set against a much louder public story built on weaker evidence. Technology Networks, echoing the Polish researchers’ framing, said social media has been flooded with claims that tiny amounts of LSD or psilocybin can steady an easily distracted mind. Donata Kurpas of Wroclaw Medical University said interest has grown because some adults do not get enough relief from standard medicines, or cannot tolerate their adverse effects. But the more encouraging signals have mostly come from naturalistic studies in which users reported short-term gains in mood, focus and emotional regulation without the controls needed to show that the substance itself caused the change. (technologynetworks.com)

The biological case, the reviewers say, is intriguing but incomplete. Psychedelics such as LSD and psilocybin mainly act through serotonergic systems and may affect neuroplasticity and large-scale brain networks. ADHD, however, is more directly linked to dopamine and noradrenaline pathways involved in motivation, impulse control and executive function. As Kurpas put it in coverage of the review: “These are biologically interesting hypotheses. However, it is important to remember that ADHD is not primarily a serotonergic disorder.” For now, any ADHD-specific benefit remains a research hypothesis rather than a demonstrated treatment effect. (technologynetworks.com)

The remaining literature is too patchy to rescue the idea. The Polish team said the review found just five eligible studies: three observational microdosing reports, one controlled LSD trial and one pilot study of ritual ayahuasca use. Those papers used different substances, different dose schedules and short follow-up periods, and most leaned heavily on self-report. That makes it hard to compare outcomes and harder still to separate a genuine drug effect from expectancy, self-monitoring and the wider setting in which people took the substances. (technologynetworks.com)

Basel’s researchers presented their study as the first placebo-controlled ADHD trial of repeated low-dose LSD in patients, a notable milestone in the Swiss city where Albert Hofman first identified the drug’s psychoactive effects in 1943. The University of Basel said the dose was chosen at the upper end of what is usually called a microdose: high enough to show a signal if one existed, but low enough to avoid disrupting daily life. The same university report said participants who believed they had received LSD improved more than those who thought they had taken placebo, prompting first author Lorenz Müller to say: “The supposed subjective treatment benefit is therefore due to the expectation of a benefit and the placebo effect rather than the actual substance.” (unibas.ch)

What follows from all this is not a rush towards off-label psychedelic treatment, but a case for better trials. Kurpas said future studies need clearer ADHD diagnoses, placebo controls, standardised protocols and longer follow-up, while also measuring what happens in everyday life, including work, relationships, sleep and emotional regulation. The researchers also want closer scrutiny of risks in people with anxiety, depression, bipolar disorder, psychosis risk or potentially interacting psychiatric medication. In material distributed by EurekAlert, Kurpas, described there as a physician and family medicine specialist at Wroclaw Medical University, said anyone already using or considering psychedelics for ADHD should discuss it with a doctor and rely on scientific evidence rather than internet testimonials. (technologynetworks.com)