Cannabis use and mood disorders: a systematic review

Summary & key facts

This systematic review looked at research up to November 2023 on cannabis use and mood disorders, especially major depressive disorder (MDD) and bipolar disorder (BD). The authors found 3,262 papers and kept 78 that fit their rules. Across those studies, cannabis use was linked with higher depressive and manic symptoms, a higher chance of later being diagnosed with MDD or BD, and a worse course or prognosis for people who already had these disorders. Most included studies were observational (only one was a randomized trial), so the evidence cannot prove cause and effect. The authors say better studies that measure type, amount, and frequency of cannabis use are needed.

Key facts:

• The literature search found 3,262 records and 78 studies met the review's inclusion criteria.
• Among the 78 included studies, only one was a randomized controlled trial; the rest were observational or non-randomized.
• Across studies, cannabis use was associated with increased depressive symptoms and increased manic symptoms in the general population.
• Studies reported that cannabis use was linked to a higher likelihood of developing major depressive disorder (MDD) and bipolar disorder (BD).
• Cannabis use was also associated with an unfavourable prognosis for people already diagnosed with MDD or BD in the reviewed studies.
• The paper notes that 192 million people reported cannabis use in 2018 and that cannabis use disorder (CUD) has been estimated at about 3% in the population.
• The review highlights that cannabis contains about 400 compounds and over 100 cannabinoids; the authors note THC is linked to psychotomimetic and anxiogenic effects, while CBD is thought to have antipsychotic and anti-anxiety properties.
• The authors emphasize a limitation: most evidence is observational and may be affected by confounding. They call for future well-designed studies that record type, amount, and frequency of cannabis use to better understand the relationship.

Abstract

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023481634.

Topics

Bipolar Disorder and Treatment Cannabis and Cannabinoid Research Child and Adolescent Psychosocial and Emotional Development

Categories

Health Sciences Medicine Psychiatry and Mental health

Tags

Anxiety Bipolar disorder Cannabis Clinical psychology Environmental health Law Major depressive disorder Medicine MEDLINE Mood Mood disorders Political science Population Psychiatry PsycINFO Systematic review

Substances

Cannabis

Conditions & symptoms

Anxiety Addiction or harmful habbits Difficulty focusing Sadness or low mood