Genetics and substance use as causal factors in the development of schizophrenia

Schizophrenia is a serious mental disorder affecting 1% of the Canadian population. It is estimated to cost Canadian Society over $2 billion per year. Many individuals with schizophrenia (80%) use and abuse substances, compounding the negative effects associated with their disorder. Much attention has recently been paid to research suggesting that the use of substances (i.e. cannabis) can cause, or is associated with a risk of developing, schizophrenia. However, previous research has failed to take into account a possible genetic role, which could be an important factor in explaining why not everyone who uses cannabis goes on to develop schizophrenia. Also, previous research has not controlled for the use of other substances; some studies have looked at cannabis but not the use of other substances (e.g. hallucinogens like LSD) which may be accounting for the additional risk of developing schizophrenia. This study will address these issues and further investigate the relationship between substance use and schizophrenia. Fifty early psychosis patients (i.e. individuals recently diagnosed with schizophrenia) and 50 healthy control individuals (i.e. without schizophrenia) will be interviewed regarding their life time history of substance use and asked to provide genetic samples for analysis. It is predicted that hallucinogen use in adolescence will increase the risk of developing schizophrenia, but only if one has a particular genetic profile. It is also predicted that individuals will be more likely to smoke if they have a particular genetic profile, and this profile will be more common in the early psychosis patients. Knowing which genetic profile confers an additional risk to developing schizophrenia if one uses particular substances (e.g. hallucinogens) will help increase knowledge about the biological components involved in this disorder as well as help to identify at-risk individuals for prevention and/or early intervention initiatives.