The differential effects of medicinal cannabis on mental health: A systematic review

Summary & key facts

Researchers looked through about 18,000 papers and found 49 controlled studies from 15 countries that tested medicinal cannabis for mental-health problems. These studies used different cannabis products, like THC and CBD alone or together. High doses of CBD sometimes gave short-term relief from anxiety. Combinations of CBD and THC helped people with cannabis withdrawal and improved sleep in some studies. But THC was the drug most linked with dose-related side effects and, in some trials, made main outcomes worse (for example, in people with psychosis). The studies had many possible biases and none showed long-lasting mental-health benefits. That means medicinal cannabis might help some symptoms for a short time, but it is not a cure and it can carry mental-health risks.

Key facts:

• The reviewers searched roughly 18,000 studies and included 49 controlled studies from 15 countries that tested medicinal cannabis for mental-health problems.
• Studies tested different products, including CBD (cannabidiol), THC (∆9-tetrahydrocannabinol), and CBD+THC combinations; the effects depended on which product was used.
• High doses of CBD were most consistently followed by some short-term relief of anxiety in clinical trials.
• Products that combined CBD and THC were reported to reduce withdrawal symptoms in people with cannabis use disorder and to improve sleep in some studies.
• THC was linked to dose-dependent adverse events and in some clinical trials was associated with worse outcomes, for example in psychosis studies.
• In studies that observed people using cannabis in normal life (naturalistic studies), some participants who used THC reported feeling better after use.
• Reviewers found many risks of bias across the studies and did not find any evidence of long-lasting mental-health improvements from medicinal cannabis.

Abstract

The use of medicinal cannabis to improve mental health is increasing globally, both in clinical settings and through self-medication. This involves a variety of products containing ∆9-tetrahydrocannabinol (THC), cannabidiol (CBD), THC + CBD combinations, or derivatives. This review provides an up-to-date overview of the positive and negative effects of medicinal cannabis on mental health diagnoses and related symptoms of the Diagnostic and Statistical Manual of Mental Disorders 5th Edition. Searches in PubMed, PsycInfo, Embase, and the Cochrane Library (October 2023 and July 2024) identified 18,341 studies, of which 49 controlled studies from 15 different countries were included. All studies focused on treatment-seeking participants using medicinal cannabis for (symptoms of) their mental health diagnosis. Included diagnoses were anxiety disorders, tic disorders, autism spectrum disorder, attention-deficit hyperactivity disorder, obsessive-compulsive disorders, anorexia nervosa, schizophrenia, psychosis, substance use disorders, insomnia, and bipolar disorders. Varying product compositions showed different effects. Most consistently, high doses of CBD were followed by some acute relief in anxiety, while CBD + THC combinations alleviated withdrawal in cannabis use disorder and improved sleep. In clinical trials, THC was associated most with dose-dependent adverse events and, in some cases, deterioration of primary study outcomes, e.g., in psychosis. In naturalistic studies, participants who used THC reported symptom improvement following usage. Risks of bias across studies were prevalent, and no study found long-lasting medicinal effects or improvement. Overall, medicinal cannabis may provide short-term relief for certain symptoms but is not a cure or without mental health risks.

Topics

Cannabis and Cannabinoid Research Prenatal Substance Exposure Effects Sleep and related disorders

Categories

Health Sciences Medicine Pharmacology

Tags

Aerospace engineering Cannabis Clinical psychology Differential (mechanical device) Engineering Mental health Psychiatry Psychology Psychotherapist

Substances

Cannabis medical cannabis

Conditions & symptoms

ADHD Anxiety Eating Disorder Obsessive-Compulsive Disorder Sleep disorder Substance abuse disorder Addiction or harmful habbits Anxiety or worry Poor sleep