Longitudinal relationship between expressed emotion and cannabis misuse in young people with first-episode psychosis.

Carers' expressed emotion (EE) and patients' cannabis misuse are two of the most robust predictors of psychotic relapse. We aimed to examine the temporal relationship between EE and cannabis misuse. Sixty-three key carers of young people with first-episode psychosis (FEP) were assessed at baseline and 7-month follow-up. EE was measured in carers using the Family Questionnaire (FQ) and cannabis misuse in patients using the Alcohol, Smoking and Substance Involvement Screening Test (ASSIST). Correlational and hierarchical logistic regression analyses were conducted to examine the temporal relationship between EE components (i.e. criticism and emotional over involvement) and cannabis misuse. Carers' criticism at baseline significantly predicted cannabis misuse according to the ASSIST at 7-month follow-up. The association remained significant after controlling for baseline symptom severity and social functioning (B=0.15, P=.02). Conversely, baseline cannabis misuse was not associated with carers' criticism at 7-month follow-up. Patients in families with high criticism showed a tendency to increase cannabis misuse over time whereas the opposite trend was observed in those with carers with low criticism. A family environment characterized by high criticism may become a key risk factor for worsening cannabis misuse over time in young people with FEP. Further studies should investigate the potential mechanisms (e.g., patient's anxiety or perceived stress) through which criticism increases cannabis misuse in FEP.