A scoping review of 39 studies found only one RCT on cannabis for ADHD (showing no significant effect), and while some studies reported symptom improvement, most showed worsening or no effect.
Read this if you have ADHD and are considering or using cannabis to manage your symptoms.
1 RCT existsOnly one randomized controlled trial has tested cannabis for ADHD — finding no significant effect
What the researchers found
Of 39 included studies, only one randomized placebo-controlled trial directly measured cannabis effects on ADHD — finding no significant effect on the primary outcome (QbTest: Est=-0.17, 95% CI -0.40 to 0.07, p=0.16). Most literature consists of cross-sectional studies examining associations between ADHD severity and cannabis use. Fifteen studies assessed neuropsychiatric effects using cognitive tests or neuroimaging. THC and CBD concentrations were poorly measured in most studies. Although some studies indicated symptom improvement, most indicated worsening or no effect.
Why it matters
Despite widespread self-medication claims, the evidence does not support cannabis for ADHD. This comprehensive scoping review provides clinicians with the strongest evidence summary available to guide patient conversations.
The numbers in context
- 39 studies included
- 1 RCT: no significant effect (QbTest Est=-0.17, p=0.16)
- 15 studies used neuropsychiatric tests or neuroimaging
- Most studies: cross-sectional design
- THC/CBD concentrations poorly measured in most studies
- Databases: MEDLINE, EMBASE, EMCARE, PsycINFO, Web of Science, Cochrane, ClinicalTrials.gov
How the study worked
Scoping review following systematic search methodology. Searched seven databases for publications in English through June 2022. Included experimental and observational studies assessing cannabis effects on ADHD symptomatology and neuropsychiatric outcomes.
Who was studied
People with ADHD across 39 studies of varying designs
What this study cannot tell us
Scoping review (broader than systematic review) with heterogeneous study designs. Most underlying studies are observational. The single RCT was not large. Cannabis exposure was poorly quantified across studies.
How to read the evidence
Comprehensive scoping review. Strong search methodology but limited by the quality of underlying studies and the absence of large controlled trials.
When this study was published
Published in 2023. Most comprehensive review of cannabis and ADHD evidence to date.
The bigger picture
The gap between patient experience ("cannabis helps my ADHD") and research evidence (mostly negative or null findings) highlights the need for rigorous clinical trials. Until such trials exist, cannabis cannot be recommended for ADHD.
Questions still open
- Would a large RCT with standardized cannabis products show different results?
- Are specific cannabinoid profiles (high-CBD) more promising for ADHD?
- Does cannabis self-medication for ADHD delay effective treatment?
Read the original research
Cannabis use in Attention - Deficit/Hyperactivity Disorder (ADHD): A scoping review.
Journal of psychiatric research, 157, 239-256
Citation
Francisco, Ana Paula; Lethbridge, Grace; Patterson, Beth; Goldman Bergmann, Carolina; Van Ameringen, Michael. (2023). Cannabis use in Attention - Deficit/Hyperactivity Disorder (ADHD): A scoping review.. Journal of psychiatric research, 157, 239-256. https://doi.org/10.1016/j.jpsychires.2022.11.029