Research That Matters (January 17 - 20, 2008)

Purpose: Research suggests that siblings of individuals with schizophrenia experience high levels of subjective burden from coping with the psychopathology and the symptomatic behaviors associated with schizophrenia. However, it has been suggested that siblings may avoid their feelings by engaging in maladaptive coping strategies such as substance use. The present study aims to examine this hypothesis by assessing the rates of substance use disorders and nicotine use in the unaffected siblings of individuals with schizophrenia, and to examine whether the psychiatric symptoms of the individual with schizophrenia impacts the pattern of substance use disorders or nicotine use in their siblings.

Methods: Participants were subjects in a clinical study of psychopathology, cognition and neuromorphology in patients with schizophrenia, their siblings, community controls, and their siblings through the Conte Center for the Neuroscience of Mental Disorders at Washington University in St. Louis. Study participants included 47 individuals with DSM-IV schizophrenia, 40 siblings of individuals with schizophrenia, 61 community controls, and 62 siblings of community controls. Both sibling groups were excluded for a lifetime history of Axis I psychotic disorders (including bipolar disorder). Community controls were also excluded if they had a first-degree relative with a psychotic disorder. Substance use disorders were defined with the Structure Clinical Interview for DSM-IV-TR (SCID) as the lifetime prevalence of abuse or dependence on alcohol or cannabis. Self-reported smoking behaviors were also assessed.

Results: Regression analyses were used in order to assess the rates of substance use disorders and nicotine use in the siblings of individuals with schizophrenia as compared to the siblings of community controls while controlling for gender and a lifetime or current diagnosis of a mood or anxiety disorder. Regression analyses were also used to examine possible relationships between patterns of psychopathology in the individuals with schizophrenia and patterns of substance use in their siblings. Siblings of individuals with schizophrenia reported higher rates of nicotine use and alcohol abuse or dependence when compared to the siblings of community controls. The two sibling groups reported statistically similar rates of cannabis use disorder, but these rates were higher than age-peers from population studies. We also found that siblings smoked more if their brother or sister was more disorganized and smoked less if he or she had more negative symptoms.

Conclusions and Implications: The main finding of this study suggests that siblings of individuals with schizophrenia have higher rates than their age peers in the general population for substance use disorders related to nicotine, alcohol, and cannabis. This emphasizes the importance of training mental health providers to work with families, in particular siblings, on improving their strategies for coping with the stress of mental illness with the goal of reducing the risk of substance use disorders.