Cannabis use is consistently associated with psychosis and progression to other drugs, with adolescent-onset use carrying the strongest psychiatric risks.
Read this if you want to understand how cannabis use relates to mental health conditions like psychosis, depression, and anxiety.
Adolescent-onset cannabis use showed the strongest associations with later psychiatric disorders
What the researchers found
This narrative review examined the relationship between cannabis use and psychiatric disorders across multiple categories. The strongest evidence linked cannabis use to psychosis and to subsequent use of other illicit substances.
The association between cannabis and bipolar disorder appeared in a few reports but remained less established. For depression and anxiety, the evidence was mixed, with some studies finding associations and others not.
Age of cannabis use emerged as a critical factor. Adolescent-onset cannabis use showed the strongest associations with later psychiatric disorders, compared to adult-onset use. The reviewers noted that most studies struggled to account for confounding factors like withdrawal symptoms, other substance use, and childhood experiences.
Why it matters
As cannabis legalization expands, understanding the psychiatric risks associated with use becomes increasingly important. This review consolidates evidence showing that the relationship between cannabis and mental health is consistently adverse when associations exist, which has implications for clinical screening and public health messaging.
The numbers in context
The review did not report pooled statistics but synthesized findings across multiple studies, concluding that "substantial evidence" supports cannabis-psychosis and cannabis-gateway associations, while depression and anxiety links remain "mixed."
How the study worked
The researchers conducted a narrative review using PubMed and PsychInfo databases, searching for literature on cannabis and psychiatric comorbidity using keywords related to cannabis, psychosis, schizophrenia, mood disorders, depression, mania, bipolar disorder, and anxiety.
What this study cannot tell us
As a narrative rather than systematic review, this study did not use standardized methods for study selection or quality assessment. Many of the reviewed studies did not adequately control for confounding factors including other substance use, withdrawal effects, or pre-existing psychiatric conditions.
How to read the evidence
Narrative review synthesizing multiple studies; moderate because it consolidates substantial evidence but lacks systematic methodology.
When this study was published
Published in 2017, this review covers literature available through 2016.
The bigger picture
This review sits within a growing body of literature highlighting adolescence as a particularly vulnerable window for cannabis-related psychiatric risk. The consistent finding that younger users face greater risk supports age-restricted access policies and targeted prevention efforts for adolescents.
Questions still open
- Does the type or potency of cannabis used influence psychiatric risk differently? Are there genetic factors that make certain adolescents more vulnerable to cannabis-related psychiatric outcomes? Would better-controlled studies change the mixed findings on cannabis-depression links?
Common questions
Does cannabis cause psychosis?
Is cannabis a gateway drug?
Read the original research
Cannabis and development of dual diagnoses: A literature review.
The American journal of drug and alcohol abuse, 43(4), 442-455
Citation
Hanna, Rebecca C; Perez, Jessica M; Ghose, Subroto. (2017). Cannabis and development of dual diagnoses: A literature review.. The American journal of drug and alcohol abuse, 43(4), 442-455. https://doi.org/10.1080/00952990.2016.1213273
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