Cannabis Use in Healthy People Linked to Psychosis and Impaired Functioning | Research

The takeaway

A systematic review of 124 studies found that cannabis use in otherwise healthy people was associated with adverse effects on cognition, mood, anxiety, psychosis risk, and social functioning, with the strongest evidence for psychosis and impaired psychosocial functioning.

Public health professionals, cannabis policy researchers, harm reduction advocates

Strongest evidence for adverse effects was in psychosis risk and psychosocial functioning

What the researchers found

Across 124 studies of cannabis effects in people without psychiatric or medical conditions, frequency of use, THC content, age of onset, and cumulative exposure all contributed to adverse behavioral outcomes including impaired cognition, motivation, mood, anxiety, psychosis risk, and psychosocial functioning.

Why it matters

By focusing exclusively on healthy individuals, this review isolates the effects of cannabis from pre-existing conditions, strengthening the case that cannabis itself contributes to these adverse outcomes rather than simply being associated with them.

The numbers in context

2,870 studies screened; 124 included; effects identified across cognition, motivation, impulsivity, mood, anxiety, psychosis, intelligence, and psychosocial functioning; strongest evidence for psychosis and psychosocial functioning; THC (not CBD) content was a key moderator.

How the study worked

PRISMA-guided systematic review of 124 cross-sectional and longitudinal studies (1990-2020) from PubMed and PsycInfo examining cannabis-related adverse behavioral outcomes in subjects without psychiatric or medical comorbidities.

What this study cannot tell us

Systematic review without meta-analysis; heterogeneity in study designs and cannabis exposure measures; cannot fully control for residual confounding even in "healthy" samples; publication bias possible.

How to read the evidence

Large systematic review of exclusively non-clinical populations, strengthened by focus on healthy individuals but limited by heterogeneity.

When this study was published

Studies from 1990-2020.

The bigger picture

The finding that THC content, but not CBD, drives adverse behavioral effects has direct implications for cannabis product regulation and suggests that products with higher CBD-to-THC ratios may carry lower behavioral risk.

Questions still open

Could CBD-dominant products avoid the adverse behavioral effects seen with THC-dominant products? At what threshold of use frequency do behavioral effects become clinically meaningful?

Common questions

Does cannabis harm healthy people?

This review of 124 studies found that cannabis use in otherwise healthy people was associated with adverse effects on cognition, mood, anxiety, psychosis risk, and social functioning, with effects driven by THC content, use frequency, and age of first use.

Does CBD cause the same problems as THC?

No. The review found that THC content, but not CBD, was associated with adverse behavioral outcomes. This suggests that CBD-dominant products may carry lower behavioral risk.

Read the original research

The Behavioral Sequelae of Cannabis Use in Healthy People: A Systematic Review.

Frontiers in psychiatry, 12, 630247

View on PubMed ↗Publisher’s paper ↗

Citation

Sorkhou, Maryam; Bedder, Rachel H; George, Tony P. (2021). The Behavioral Sequelae of Cannabis Use in Healthy People: A Systematic Review.. Frontiers in psychiatry, 12, 630247. https://doi.org/10.3389/fpsyt.2021.630247