Journal Article Annotations
2020, 2nd Quarter
Annotations by Walter Luchsinger, MD
June 26, 2020
That acute administration of THC induces significant increases in positive, negative, general, and total symptoms with large effect sizes in adults with no history of psychotic or other major psychiatric disorders. Notably, effect sizes were greater for positive symptoms than for negative symptoms but not for general symptoms, indicating that THC induces positive symptoms to a greater extent than negative symptoms. By contrast, CBD does not induce psychiatric symptoms, and there is inconclusive evidence that it moderates the induction of psychiatric symptoms by THC. These effects are larger with intravenous administration than with inhaled administration, and tobacco smokers have less severe positive symptoms.
This was asystematic review and meta-analysis. A strength of the analysis is that it focused on experimental studies with placebo control conditions, which avoids the risk of reverse causality and residual confounding factors associated with observational studies of psychotic symptoms in cannabis users.
A number of study limitations should be considered in evaluating the findings. Many of the meta-regression analyses comprised fewer than 10 studies and so were underpowered to detect small-to-moderate effects. Thus, we cannot exclude a modifying effect of some variables on the findings, in particular tobacco use and THC dose on the induction of total, negative, or general symptoms by THC, or age or gender on general symptoms, although our analyses suggest that any potential effects are not large. There was a preponderance of male-dominated samples in the studies. Although no effect of sex was identified, future studies should include more females to ensure generalizability. There was potential publication bias in positive, negative, and total symptom domains. This bias might be due to selective reporting of symptom scales with significant findings. Nevertheless, effect sizes for positive symptoms were positively associated with study quality, suggesting that these findings might be underestimating effect size as a result of the inclusion of lower quality studies that have smaller effect sizes. Findings remained largely unchanged after adjusting for putatively missing studies. Finally, the use of summary symptom measures that combine scores across several symptoms precluded analysis of individual symptoms.
The findings are highly relevant as medical, societal, and political interest in cannabinoids continues to grow.
Type of study
A Systematic Review and Meta-analysis