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Medical Marijuana and Adult ADHD

Is it helpful? What is the status of the science?

I’m a psychologist whose specialty is cognitive-behavior therapy (CBT) adapted for adult attention-deficit/hyperactivity disorder (ADHD). In recent years, when someone perks up at the mention of my specialty, it is likely due to mishearing the acronym C-B-T as C-B-D, which stands for cannabidiol, one of the chemical agents in cannabis sativa plants. Once clarified, the listener’s countenance typically returns to one of polite disinterest.

On a serious note, with the increasing legalization of cannabis-based products and prescription “medical marijuana,” attention is turning towards their potential uses for ADHD, often based on anecdotal accounts. It seems to be a good time to take stock of the current science regarding these assertions. It should be noted that this overview only focuses on claims about the therapeutic effects of cannabis preparations for adults with ADHD. It is not a commentary on the legalization or decriminalization of marijuana use.

The United States’ Food and Drug Administration (FDA) has not approved any cannabis-derived products for the treatment of ADHD. The FDA has approved one cannabis-derived product and three cannabis-related products that require prescriptions from a licensed healthcare provider. These products target seizure activity from specific conditions and anorexia associated with weight loss in patients with AIDS.

Let's fact check whether medical marijuana helps ADHD!
Source: Pixabay/Pexels

General misinformation on marijuana use for ADHD abounds. A study of online forum content over a decade (2004-2014) revealed widespread anecdotes and testimonials to the benefits of “weed” for ADHD.1 A review of public forum posts found that 30% promoted cannabis as helpful for ADHD (25% cited it as helpful and 5% as both helpful and harmful); whereas 8% found it harmful and 2% reported no effects on ADHD. The suggested benefits of cannabis did not generalize to non-ADHD symptoms or coping in various life domains, at least based on descriptions on forum posts. What is more, 59% of the forums studied included posts extolling the benefits of cannabis for ADHD. In some cases, the benefits were tied to specific symptoms of ADHD in the diagnostic criteria (the inattentive domain, mainly); others described indiscriminate benefits for ADHD, simply that it helped somehow. The view of cannabis as having positive effects for ADHD has been consistently higher since 2006 and increasingly justified by the increasing endorsement of the benefits of medical marijuana and its availability as a “natural” alternative.

The questions related to the safety and effectiveness of cannabis-based products deserve good research. There have been media accounts of studies showing positive results, though closer inspection usually reveals that these are from preliminary studies presented as papers at conferences. Such papers have not undergone rigorous peer review for journal publication (and only about half of such conference papers are published2).

That being said, regarding tetrahydrocannabinol (THC) in medical or recreational marijuana use, there is no evidence that THC provides any benefits related to adult ADHD and its use is not recommended for ADHD at any age.3 Along with CBD, THC is the most common cannabinoid in use. THC is the chemical associated with the “high” commonly associated with marijuana. Apart from the absence of evidence for the therapeutic use of THC, there are many known adverse effects of recreational THC use on brain development4 that are more pronounced for teens with ADHD5 that should discourage its use, not to mention the risk for substance use disorders.

CBD is more commonly used in therapeutic preparations, as it does not have the psychoactive effects of THC. Although the study of CBD for psychiatric conditions is still at an early stage, there is initial, tentative support for its use with social anxiety and some mixed results (leaning to the positive) as an adjunct in the treatment of schizophrenia, though there are cautions about the use of high-THC compounds for those with schizophrenia or anxiety.6 Regarding ADHD, however, recent, thorough reviews of published studies did not find any established support for the benefits of CBD for adult ADHD7,8.

A well-designed pilot, randomized, placebo-controlled study using nabiximol oromucosal spray in a 6-week study of 30 adults with ADHD was conducted.9 There were non-significant improvements in the cognitive performance on a computerized continuous performance task when compared with the control group; and nominally significant improvements in clinician-ratings of symptoms of hyperactivity-impulsivity and inhibition, and a trend towards significance for inattention symptoms (though the results were non-significant after adjustments were made for multiple testing, but provided data that this CBD preparation at least did not impair performance). There were 4 adverse events in the active-treatment group and one in the placebo group that, along with the non-significant results did not provide evidence to support its use.

There should be more research on this front. It is important to have effective treatments for ADHD. As it stands now, however, there is no empirical support for use of medical marijuana for the symptoms of ADHD.


1 Mitchell, J. T., Sweitzer, M. M., Tunno, A. M., Kollins, S. H., & McClernon, F. J. (2016) “I use weed for my ADHD”: A qualitative analysis of online forum discussions on cannabis use and ADHD. PLoS ONE 11(5): e0156614. doi:10.1371/journal.pone.0156614

2 Dumas-Mallet, E., & Gonon, F. (2020). Messaging in biological psychiatry: Misrepresentations, their causes, and potential consequences. Harvard Review of Psychiatry, 28(6), 395-403. doi: 10.1097/HRP.0000000000000276

3 Canadian ADHD Resource Alliance (2020). Cannabis and ADHD: A CADDRA policy statement. Canadian ADHD Resource Alliance.

4 Volkow, N. D., et al. (2014). Adverse effects of marijuana use. New England Journal of Medicine, 370, 2219–2227. doi:10.1056/NEJMra1402309

5 Tamm, L., et al. (2013). Impact of ADHD and cannabis use on executive functioning in young adults. Drug and Alcohol Dependence, 133(1), 607-614. doi:10.1016/j.drugalcdep.2013.08.001

6 Noel, C. (2017). Evidence for the use of “medical marijuana” in psychiatric and neurologic disorders. Mental Health Clinician, 7(1), 29-38. doi: 10.9740/mhc.2017.01.029

7 Black, N., et al. (2019). Cannabinoids for the treatment of mental disorders and symptoms of mental disorders: a systematic review and meta-analysis. Lancet Psychiatry, 6, 995-1010.

8 Sarris, J., et al. (2020). Medicinal cannabis for psychiatric disorders: a clinically-focused systematic review. BMC Psychiatry, 20(24).…

9 Cooper R. E., et al. (2017). Cannabinoids in attention-deficit/hyperactivity disorder: a randomized controlled trial. European Neuropsychopharmacology, 27(8), 795–808.

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