Effect of cannabis on weight and metabolism in first-episode non-affective psychosis: Results from a three-year longitudinal study.

Cannabis smoking is highly prevalent among patients with psychotic disorders. Its use has been found to be related to clinical characteristics and the prognosis of the disorder. Recent evidence indicates a protective effect of cannabis on weight gain and related metabolic alterations. However, there are no previous studies on the long-term longitudinal effects of cannabis on first-episode drug-naïve patients, which would thereby avoid the confounding effects of chronicity and previous treatment exposure. We aimed to explore the effect of cannabis smoking on weight and lipid/glycaemic metabolic measures in a sample of first-episode non-affective psychosis patients.Anthropometric measurements and glycaemic and lipid parameters were obtained at baseline and three years after initiation of treatment. Patients self-reported their cannabis use at both time points. To explore the longitudinal effect of cannabis, patients were divided into three groups: continuers, discontinuers and non-users.Cannabis users at baseline presented a lower weight ( F=14.85, p<0.001), body mass index ( F=13.14, p<0.001), total cholesterol ( F=4.85, p=0.028) and low-density lipoprotein-cholesterol ( F=6.26, p=0.013) compared to non-users. These differences were also observed after three years: weight ( F=8.07, p=0.005), body mass index ( F=4.66, p=0.032) and low-density lipoprotein-cholesterol ( F=3.91, p=0.049). Moreover, those patients discontinuing cannabis use presented a higher increase in weight ( F=2.98, p=0.052), body mass index ( F=2.73, p=0.067) and triglyceride-high-density lipoprotein ratio ( F=2.72, p=0.067) than the 'non-users' and 'continuers'.The study suggests that cannabis use may produce a protective effect against weight gain and related metabolic alterations in psychosis. However, these results need to be replicated in a larger sample size.