Abstract

Continued cannabis use (CCu) is an important predictor for poor long-term outcomes in psychosis and clinically high-risk patients, but no generalizable model has hitherto been tested for its ability to predict CCu in these vulnerable patient groups. In the current study, we investigated how structured clinical and cognitive assessments and structural magnetic resonance imaging (sMRI) contributed to the prediction of CCu in a group of 109 patients with recent-onset psychosis (ROP). We tested the generalizability of our predictors in 73 patients at clinical high-risk for psychosis (CHR). Here, CCu was defined as any cannabis consumption between baseline and 9-month follow-up, as assessed in structured interviews. All patients reported lifetime cannabis use at baseline. Data from clinical assessment alone correctly classified 73% (p < 0.001) of ROP and 59 % of CHR patients. The classifications of CCu based on sMRI and cognition were non-significant (ps > 0.093), and their addition to the interview-based predictor via stacking did not improve prediction significantly, either in the ROP or CHR groups (ps > 0.065). Lower functioning, specific substance use patterns, urbanicity and a lack of other coping strategies contributed reliably to the prediction of CCu and might thus represent important factors for guiding preventative efforts. Our results suggest that it may be possible to identify by clinical measures those psychosis-spectrum patients at high risk for CCu, potentially allowing to improve clinical care through targeted interventions. However, our model needs further testing in larger samples including more diverse clinical populations before being transferred into clinical practice.

Highlights

  • Cannabis use has a prominent role in the development of psychosis[1,2], and exacerbates the course of the full-blown psychotic disorder[3,4]

  • In patients at clinical high-risk for psychosis (CHR) reporting lifetime cannabis use, continued cannabis use (CCu) after experiencing attenuated psychotic symptoms increased the risk of transition[7]

  • The environmental risk factors for CCu, and the presence of cognitive deficits have been individually associated with cannabis use in general, and with an increased risk for psychosis[26,27]

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Summary

Introduction

Cannabis use has a prominent role in the development of psychosis[1,2], and exacerbates the course of the full-blown psychotic disorder[3,4]. Patients with psychosis who are habitual cannabis users have distinctly worse long-term outcome compared to those without concurrent cannabis use in terms of re-hospitalization, the severity of psychotic symptoms and general functioning[5]. In first episodes of psychosis, cannabis use is reportedly among the most powerful predictors of relapse to psychosis[6]. In patients at clinical high-risk for psychosis (CHR) reporting lifetime cannabis use, continued cannabis use (CCu) after experiencing attenuated psychotic symptoms increased the risk of transition[7]. The number of individuals with cannabis use disorder has increased worldwide in recent years[8], with correspondingly high rates of cannabis use disorder reported in early psychosis patients[9]. The vulnerability to Published in partnership with the Schizophrenia International Research Society

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