Schizophrenia and substance use disorder: a retrospective study of a dual diagnosis patients cohort

Introduction: Approximately 47% of patients with Schizophrenia have criteria for a dual diagnosis. The consumption of illicit substances, particularly cannabis, is quite prevalent in these patients, being associated with an increase in mortality and morbidity and worse social outcomes. This study aims to understand the relationship between Schizophrenia and substance use disorders (SUD). Material and methods: A retrospective study was designed, including patients diagnosed with schizophrenia admitted to the Psychiatric Ward between January 2017 and June 2019. Results: 205 patients were included, 49 women (23.9%) and 156 men (76.1%). Of these, 29.1% consumed psychoactive substances at the first hospitalization, mainly cannabis (24.1%), with higher prevalence in men. The average age at the first admission was significantly lower for substance users than for non-users. The presence of consumption in the first hospitalization, the number of hospitalizations and treatment adherence were associated with the maintenance of consumption after the first hospitalization. The presence of consumption at the first hospitalization is a significant predictor of its maintenance. Patients who do not adhere to treatment were more likely to maintain consumption. The number of future hospitalizations was associated with early age at the first hospitalization, non-compliance to treatment and maintenance of consumption after the first hospitalization. Conclusions: We verify that the consumption of psychoactive substances is associated with the early age at the first hospitalization, whit the reduced compliance to treatment and the increased number of hospitalizations. Comorbid substance use disorders should be treated as early as possible to minimize the long-term effects of substance use on patients with schizophrenia in Dual Diagnosis programs.