Background: Abnormalities in early social development and personality are present in patients with schizophrenia and their unaffected relatives. This study aimed to establish the degree to which these childhood and adolescent developmental abnormalities are genetically determined.
Method: We used a combined twin and family study design (n=531) to assess childhood and adolescent social adjustment and schizotypal personality traits in 98 twin pairs (n=196) varying in their zygosity and concordance for schizophrenia and 156 sibling clusters (n=335) varying in their concordance for schizophrenia.
Results: Schizophrenia was significantly associated with childhood and adolescent deficits in social adjustment and personality, with additive genetic effects being the main source of these phenotypic correlations.
Conclusions: Abnormalities of social adjustment and personality are present in children and adolescents who later develop schizophrenia, reflecting the influence of common genetic risk.