Severe mental illness (SMI) refers to the most burdensome psychiatric conditions. The need to pre-empt the onset of SMI is pressing because once SMI develops, quality of life is poor and available treatments have limited efficacy. Most risk factors for SMI are either unchangeable (e.g., genetics) or difficult to alter (e.g., low socio-economic status). In contrast, cannabis use is one specific risk factor that could be avoided. Certain individuals are more vulnerable to the harmful effects of cannabis. Genetic factors can help us identify these high-risk individuals. One in three individuals are carriers of a higher-risk genetic variant, and cannabis users with this genotype are at up to 7-fold increased risk of developing schizophrenia. In our study, genetic counselling will be provided to participants by a board-certified genetic counsellor. During the genetic counselling session, participants will have the option to receive their genotype. Participants will be counselled regarding their individualized risk of developing and of not developing SMI based on family history, whether or not they choose to use cannabis, and genotype (if the participants accept the genetic test results). The investigators hypothesize that this intervention will reduce exposure to cannabis compared to the youth who are not offered the intervention.

NCT03601026

Conditions

1. Mental Illness
2. Schizophrenia
3. Bipolar Disorder
4. Major Depressive Disorder
5. Cannabis Use
6. Psychosis

Interventions

1. Behavioral: Genetic counselling

MeSH:Disease Marijuana Abuse Schizophrenia Depressive Disorder Depressive Disorder, Major Bipolar Disorder Mental Disorders

HPO:Bipolar affective disorder Depressivity Mania Schizophrenia

A replicated gene-cannabis interaction shows that carriers of a common genetic variant (C alleles at rs2494732 in the AKT1 gene) are at up to 7-fold increased risk of developing psychosis if they use cannabis.