Twins discordant for schizophrenia: psychopathology of the non-schizophrenic co-twins

Objective: Patients with schizophrenia are more likely to suffer from mood and anxiety disorders compared with the general population. We explored the aetiology of this comorbidity using a twin study design. Method: We applied an additive genetic + unique environment (AE) random effects model in the analysis of 35 non-schizophrenic co-twins from pairs discordant for schizophrenia, and 131 control twins. Results: Non-schizophrenic co-twins had significantly increased rates of depression (P = 0.006) and anxiety disorders (P = 0.021) compared with the control twins. Conclusion: Our results provide evidence for a familial association between schizophrenia and anxiety and depression. This could reflect common aetiological factors contributing to each of the disorders. Future studies should attempt to investigate the relative genetic and environmental contribution to the shared risk factors for schizophrenia, mood and anxiety disorders.