The Impact of Pre-onset Cannabis Use on Age at Onset of Prodromal and Psychotic Symptoms

Schizophrenia is currently conceptualized as an illness that is caused by both genetic predispositions and exposure to stressors or environmental factors, particularly during early childhood and adolescence. This article focuses on one such environmental factor, cannabis use, especially use occurring prior to the onset of clinically evident psychiatric symptoms. Cannabis is commonly abused by adolescents and is the most abused illicit drug in the context of schizophrenia. Several first-episode studies document that the initiation of substance use and abuse typically precedes the onset of psychosis. This article highlights eight studies that characterize the impact of cannabis use on the age at onset of psychosis and three studies that provide early information on the impact of cannabis use on the age at onset of even earlier prodromal symptoms. Future research is needed to better characterize the impact of cannabis use on the onset of psychotic disorders and to determine if cannabis use increases the risk of developing a psychotic disorder, as several other studies suggest. Based on emerging evidence, preventing or reducing cannabis use among adolescents, particularly those at elevated risk of developing psychosis, may delay the onset of psychosis in some. The Impact of Pre-onset Cannabis Use on Age at Onset of Prodromal and Psychotic Symptoms