Mind the gap: An insight into the temporal relationship between initiation of cannabis use and onset of psychosis

Abstract

Background: Evidence pointing towards a causal relationship between cannabis use and psychotic disorders is growing. Several studies have hypothesized the cumulative effects of cannabis use and its risk of psychosis onset. Our aim is to further study the temporal relationship between age at onset of cannabis use and first psychosis episode. Methods: The study sample consisted of 36 patients previously diagnosed with cannabis-induced psychotic disorder and receiving treatment at the psychiatry department of Centro Hospitalar Universitário de São João. Data was collected during regular consultations and from clinical registries, including self-reported drug use and information on age at onset of psychosis and age at onset of use. Results: The median duration of pre-morbid cannabis exposure was 8 years (IQR:11). The median age at onset of cannabis use was 17 years old (IQR: 10) and mean age at onset of psychosis was 28.82 years old (SD: 8,14). Men comprised 89% of this sample. 80.96% of patients suffered psychotic relapse, with a median time until recurrence of 3 years (IQR:5). 72.2% of patients that presented with recurrent psychosis were using cannabis. Only 25% of all patients recovered their pre-morbid functionality level. No significant difference in duration pre-morbid cannabis exposure was found according to sex or other illicit drug use. Conclusion: These findings reinforce the negative social and medical impact of this diagnosis, and the need for timely and appropriate interventions to reduce the burden of this disease.