Symptomatology and neurocognition among first-episode psychosis patients with and without cannabis use in the three months prior to first hospitalization.

Objective: The nature of associations between recent cannabis use and negative symptoms, positive symptoms, and neurocognitive deficits remains unclear. In a relatively large sample of well-characterized patients with first-episode psychosis, we hypothesized that, compared to first-episode patients without cannabis use in the three months prior to first hospitalization, those having used cannabis would have lesser negative symptoms, greater positive symptoms, and no differences in cognitive functioning. Dose-response relationships were also examined.

Methods: Between 2008 and 2013, 247 first-episode psychosis patients were assessed during their hospitalization at one of six participating inpatient psychiatric units. Measures included the Longitudinal Substance Use Recall for 12 Weeks instrument, the Scale for the Assessment of Negative Symptoms, the Scale for the Assessment of Positive Symptoms, and the MATRICS Consensus Cognitive Battery (MCCB).

Results: Anhedonia-asociality was significantly lower among those using cannabis in the past three months (10.7±4.6 v. 12.1±4.4, p=.023). Delusions were more severe among those having used cannabis (19.3±8.4 v. 15.9±9.1, p=.005), as was bizarre behavior (p=.01). There were no significant differences between those using and not using cannabis across nine MCCB measures. Correlations between the "dose" of cannabis and all of these measures were not significant.

Conclusions: Compared to those without cannabis use, those who use cannabis in recent months have lesser anhedonia-asociality, greater delusion and bizarre behavior severity, and no significant differences in neurocognition. Such characterizations could shed light on subgroups of individuals with first-episode psychosis, as well as risk factors for cannabis use in the early course of these disorders.