Motivational interviewing and interaction skills training for parents to change cannabis use in young adults with recent-onset schizophrenia: a randomized controlled trial

Background. Cannabis use by people with schizophrenia has been found to be associated with family distress and poor clinical outcomes. Interventions to reduce drug use in this patient group have had limited efficacy. This study evaluated the effectiveness of a novel intervention for parents of young adults with recent-onset schizophrenia consisting of family-based motivational interviewing and interaction skills (Family Motivational Intervention, FMI) in comparison with routine family support (RFS). Method. In a trial with 75 patients who used cannabis and received treatment for recent-onset schizophrenia, 97 parents were randomly assigned to either FMI (n=53) or RFS (n=44). Assessments were conducted at baseline and 3 months after completion of the family intervention by an investigator who remained blind throughout the study about the assignment of the parents. Results. At follow-up, patients' frequency and quantity of cannabis use was significantly more reduced in FMI than in RFS (p<0.05 and p<0.04 respectively). Patients' craving for cannabis was also significantly reduced in FMI whereas there was a small increase in RFS (p=0.01). There was no difference between FMI and RFS with regard to patients' other substance use and general level of functioning. Both groups showed significant improvements in parental distress and sense of burden. Conclusions. Training parents in motivational interviewing and interaction skills is feasible and effective in reducing cannabis use among young adults with recent-onset schizophrenia. However, FMI was not more effective than RFS in increasing patients' general level of functioning and in reducing parents' stress and sense of burden.