Elevated rates of substance use disorders in non-psychotic siblings of individuals with schizophrenia

Background: Individuals with schizophrenia use psychoactive substances more frequently than the general population. The genetic vulnerability to develop schizophrenia may also increase risk for the development of substance use disorders. We examine this hypothesis by assessing the rates of substance use disorders and nicotine use in non-psychotic siblings of individuals with schizophrenia. Methods: Participants included 59 individuals with DSM-IV schizophrenia, 53 of their siblings, 80 community controls, and 75 of their siblings. Statistical regression was used to assess the rates of substance use disorders and nicotine use in study participants while controlling for age, gender, lifetime diagnosis of a mood or anxiety disorder, and a family history of substance use disorder. Results: Individuals with schizophrenia and their non-psychotic siblings reported higher rates of alcohol and cannabis use disorders and nicotine use when compared to siblings of comparison subjects. Conclusions: The vulnerability to develop schizophrenia may also extend to substance use disorders. Future research is needed to investigate the neurobiological basis of increased substance use in non-psychotic siblings and the psychosocial mechanisms that may contribute to increased substance use in non-psychotic siblings.