The plant may keep the stimulant from working
STUDY: Levin FR et al, J Atten Disord 2024
STUDY TYPE: Randomized, double-blind, placebo-controlled trial
FUNDING: National Institute on Drug Abuse/NIH
Background
Cannabis causes symptoms of ADHD, impairing attention and executive function. But ADHD raises the risk of substance use disorders. It’s hard to know which came first, and many clinicians treat with stimulants in hopes of reducing ADHD and substance use.
Earlier attempts to treat ADHD during cannabis use failed — including trials of methylphenidate, amphetamines, as well as non-stimulants like atomoxetine and pimozide. These authors wondered if pushing the dose higher could make the difference.
The Study
- 28 adults with comorbid ADHD and cannabis use disorder, use nearly every day at baseline.
- Randomized to Adderall XR up to 80 mg/day or placebo for 12 weeks, with weekly visits.
- Primary outcomes were at least 30% reduction on the ADHD rating scale (AISRS) and two-week cannabis abstinence at the end of the trial.
- Double-blind.
Neither primary outcome separated from placebo. ADHD response rates were 83% with active medication versus 71% with placebo. Cannabis abstinence was 15% versus 0%, a meaningful-looking gap that wasn’t statistically significant given the tiny sample. On the other hand, the active medication group reduced weekly cannabis use days by about 23% per week over the course of the trial, compared to no change in the placebo group.
Side Effects
One participant on active medication developed atrial fibrillation deemed study-related. Insomnia, anxiety, and chest pain were more common in the active arm but not significantly so.
Limitations: Small size, high placebo response rate, high drop-out and non-adherence rates.
Practice Implications
- On the one hand, the studies limitations make it uninterpretable.
- On the other hand, the fact that four earlier trials failed to make a difference suggest we need to inform patients that cannabis may completely block their ADHD meds from working. This is a difficult conversation, as social media suggests many cannabis users think it treats ADHD.
- In another study, cannabis worsened cognition while users though it was improving it.
— Chris Aiken, MD
Director, Psych Partners
Editor in Chief, Carlat Psychiatry Report
One comment
KT
August 12, 2026 at 7:05 pm
Thank you so much for sharing this. It was very helpful and reassuring.
As a provider, I’ve experienced pushback from both patients and therapists when discussing ADHD and marijuana use. When I try to educate patients about marijuana use and its potential complications—including effects on mood, anxiety, sleep, and cognition, as well as the increased risk of psychosis and other psychiatric complications, particularly in younger patients—I have at times encountered resistance or concerns that bringing up these risks may come across as judgmental. I understand that cannabis use can be a sensitive topic, but my intention is to approach these conversations from a place of education and clinical concern rather than judgment.
My intention is never to judge a patient’s choices or dictate whether they should use marijuana. My goal is to provide education, explore their reasons for using it, and encourage reduction or discontinuation when clinically appropriate. I also think it is important to consider whether cannabis use may be contributing to or exacerbating symptoms, particularly when its effects can overlap with symptoms of ADHD or other psychiatric conditions.
I’m glad to see evidence highlighting the importance of considering cannabis use when assessing and treating ADHD. It reinforces for me that discussing marijuana use as part of an ADHD assessment and treatment plan is not about being judgmental; it is about providing patients with accurate information and doing what we can to optimize their treatment.
Thank you again for sharing this. I really appreciate it.