Effects of repeated low-dose LSD on neuropsychological functioning in adults with ADHD: a randomized placebo-controlled study
E. C. H. M. Haijen-Bongers, Petra P M Hurks, J. Schepers, Patrick Vizeli, Joyce Santos de Jesus, L. Mueller, Yasmin Schmid, M.e. Liechti, K.p.c. Kuypers
Psychopharmacology June 20, 2026 DOI: 10.1007/s00213-026-07107-7 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Randomized controlled trial Placebo-controlled Double-blind Peer reviewed |
|---|---|
| Sample size | 53 |
| Population | Adults with attention-deficit hyperactivity disorder |
| Intervention | Lysergic acid diethylamide (LSD) |
| Dose | 20 µg |
| Duration | 6-week biweekly treatment |
| Topics | LSD |
| Keywords | Neuropsychology Placebo Cognition Population Randomized controlled trial Young adult Continuous performance task Clinical psychology Audiology Developmental psychology Neuropsychological assessment Repeated measures design |
| Registration | NCT05200936 |
| Key findings | Low-dose LSD treatment showed an effect on temporal processing (time reproduction) but not on other neuropsychological domains in adults with ADHD. |
Abstract
Rationale: Attention-deficit hyperactivity disorder (ADHD) shows substantial heterogeneity in symptoms and cognitive deficits. According to the Triple Pathway Model, this variability may stem from impairments in three neuropsychological domains: inhibition, motivation, and temporal processing. Repeated low-dose administration of psychedelics is being explored as a treatment for ADHD, but evidence from controlled studies in this population remains limited.
Objectives: This study investigated performance across neuropsychological domains relevant to ADHD: attention, inhibition, motivational processing, and temporal processing, before and after a six-week biweekly low-dose lysergic acid diethylamide (LSD) treatment (20 µg) in adults with ADHD. Based on previous findings, we expected improvements in attention and temporal processing and explored whether baseline ADHD symptoms and domain-specific task performance predicted treatment outcomes.
Methods: This study presents a secondary analysis of a double-blind, placebo-controlled, parallel group trial. Performance on objective behavioral tasks was assessed at baseline and after six weeks of treatment, before intake of the final dose.
Results: Fifty-three patients were randomized to LSD (n = 27) or placebo (n = 26), and 46 completed the study (LSD: n = 23; placebo: n = 23). An effect of LSD was observed on temporal processing (Time Reproduction Task), leaving performance on other tasks unaffected. Exploratory analyses indicated that baseline performance differentially predicted outcomes related to inhibition and time reproduction in the LSD and placebo groups.
Conclusions: These findings do not provide convincing evidence for broad cumulative benefits of low-dose LSD treatment across neuropsychological domains in adults with ADHD. The observed effect was limited to a single time reproduction measure and should be interpreted cautiously, particularly given the absence of corresponding improvements in clinical symptoms in the parent trial. Future studies should investigate the robustness of this finding and whether effects are acute, cumulative, or subgroup-specific. REGISTRY: ClinicalTrials.gov, TRN: NCT05200936, Registration date: 21 December 2021.
Comparable studies
Other randomized controlled trials on LSD, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Safety and Efficacy of Lysergic Acid Diethylamide-Assisted Psychotherapy for Anxiety Associated With Life-threatening Diseases Patients with anxiety associated with life-threatening diseases | 2014 | Randomized controlled trial | n = 12 |
| Dose-Response Study of N,N-Dimethyltryptamine in Humans Experienced hallucinogen users | 1994 | Double-blind, saline placebo-controlled, randomized study | n = 12 |
| Acute Effects of Lysergic Acid Diethylamide in Healthy Subjects Healthy subjects (8 women, 8 men) | 2014 | Double-blind, randomized, placebo-controlled, crossover study | n = 16 |
| Changes in global and thalamic brain connectivity in LSD-induced altered states of consciousness are attributable to the 5-HT2A receptor Healthy human participants | 2018 | Double-blind, randomized, counterbalanced, cross-over study | n = 24 |
| LSD-induced entropic brain activity predicts subsequent personality change. Healthy adults | 2016 | Balanced-order, placebo-controlled study | n = 19 |
Citations in the library
Cites 15
- The effects of microdose LSD on time perception: a randomised, double-blind, placebo-controlled trial Psychopharmacology November 26, 2018
- Mood and cognition after administration of low LSD doses in healthy volunteers: A placebo controlled dose-effect finding study European Neuropsychopharmacology October 17, 2020
- Effects of varied doses of psilocybin on time interval reproduction in human subjects Neuroscience Letters February 13, 2008
- Self-Rated Effectiveness of Microdosing With Psychedelics for Mental and Physical Health Problems Among Microdosers Frontiers in Psychiatry September 13, 2019
- Psilocybin microdosing does not affect emotion-related symptoms and processing: A preregistered field and lab-based study Journal of Psychopharmacology December 17, 2021
and 10 more in the library