Cannabis-Using Schizophrenia Patients Gained Less Weight on Antipsychotics | Research

The takeaway

First-episode schizophrenia patients who tested positive for cannabis gained significantly less weight during 12 months of antipsychotic treatment compared to non-users, with no significant difference in metabolic markers.

Psychiatrists, patients on antipsychotics, metabolic health researchers.

Cannabis-positive patients showed significantly less BMI increase over 12 months (p=0.002) and fewer metabolic changes than cannabis-negative patients.

What the researchers found

There was a significant group-by-time interaction (p=0.002): cannabis-negative patients showed greater BMI increases over 12 months than cannabis-positive patients. Post hoc tests showed the cannabis-negative group had significant increases in fasting glucose, triglycerides, and decreased HDL cholesterol, while the cannabis-positive group showed no significant changes in these markers.

Why it matters

Antipsychotic-induced weight gain is a major side effect that contributes to cardiovascular disease and treatment non-adherence. Understanding why some patients gain less weight could lead to better metabolic management strategies.

The numbers in context

109 patients total: 40 cannabis-positive, 69 cannabis-negative. Significant group-by-time interaction for BMI (p=0.002). More cannabis-negative patients had elevated waist circumference at endpoint (p=0.003).

How the study worked

109 minimally treated first-episode patients with schizophrenia-spectrum disorders received standardized depot antipsychotic treatment over 12 months. 40 tested positive for cannabis at any point; 69 tested negative at all time points. Repeated measures compared BMI, fasting glucose, and lipids over time.

What this study cannot tell us

Observational within a treatment study - cannot prove cannabis caused the weight difference. Cannabis users may have different lifestyle factors (diet, smoking). Urine testing only indicates recent use, not quantity or frequency.

How to read the evidence

Moderate - prospective cohort with standardized treatment and objective cannabis testing, but observational comparison with potential confounders.

When this study was published

Published in 2018.

The bigger picture

While acute cannabis use stimulates appetite, chronic use may actually suppress it. This study adds clinical evidence to population-level findings linking regular cannabis use with lower obesity rates, specifically in a context where weight gain is a major clinical concern.

Questions still open

Is the weight difference directly caused by cannabis or by associated lifestyle factors? Could cannabinoid-based medications be developed to counteract antipsychotic weight gain? Does the metabolic benefit outweigh the psychiatric risks of cannabis use in schizophrenia?

Common questions

Does cannabis affect weight gain from antipsychotics?

This study found that schizophrenia patients who tested positive for cannabis gained significantly less weight during 12 months of antipsychotic treatment. They also showed fewer negative metabolic changes in blood sugar and cholesterol.

Does chronic cannabis use affect body weight?

While cannabis acutely stimulates appetite ("the munchies"), this and other studies suggest chronic use may actually be associated with lower body weight. The mechanisms are not fully understood.

Read the original research

Effects of cannabis use on body mass, fasting glucose and lipids during the first 12 months of treatment in schizophrenia spectrum disorders.

Schizophrenia research, 199, 90-95

View on PubMed ↗Publisher’s paper ↗

Citation

Scheffler, F; Kilian, S; Chiliza, B; Asmal, L; Phahladira, L; du Plessis, S; Kidd, M; Murray, R M; Di Forti, M; Seedat, S; Emsley, R. (2018). Effects of cannabis use on body mass, fasting glucose and lipids during the first 12 months of treatment in schizophrenia spectrum disorders.. Schizophrenia research, 199, 90-95. https://doi.org/10.1016/j.schres.2018.02.050