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

Summary & key facts

This paper looked across many studies to see how medical cannabis products affect mental health. The authors screened about 18,300 records and included 49 controlled studies from 15 countries that tested products containing THC, CBD, or both. They found that different medicines had different short-term effects: high doses of CBD often gave quick relief for anxiety; CBD plus THC helped with withdrawal from cannabis and with sleep; but THC was most linked to dose-related side effects and sometimes made symptoms worse, for example in people with psychosis. Most studies had problems that make their results uncertain, and none showed lasting mental-health improvements. That means medical cannabis might help some symptoms briefly, but it is not a cure and has real mental-health risks.

Key facts:

• The review searched major medical databases and screened about 18,300 records, then included 49 controlled studies from 15 countries that focused on people using medical cannabis for mental-health problems.
• High doses of cannabidiol (CBD) were the finding most consistently linked to short-term relief of anxiety symptoms in clinical trials.
• Combinations of CBD and THC were reported to reduce withdrawal symptoms in people with cannabis use disorder and to improve sleep in some clinical trials.
• Products containing THC were most often associated with dose-related adverse effects and, in some controlled trials, made primary outcomes worse—for example, worsening symptoms in people with psychosis in at least one study.
• Many of the included studies had risks of bias or other design problems, which makes their findings less reliable.
• No study in this review found long-lasting medicinal effects on mental-health diagnoses or related symptoms; benefits were short term at best.

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

Conditions & symptoms

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