Family history of schizophrenia, BD increases autism risk

By Mark Cowen

A history of schizophrenia or bipolar disorder (BD) in first-degree relatives is associated with a significantly increased risk for autism spectrum disorders (ASDs), study results suggest.

The team found that having a parent with schizophrenia was associated with almost a threefold increased risk for ASDs, while having a sibling with the condition increased the risk more than twofold.

The increased risk for ASDs associated with a family history of BD was less elevated, however.

"Our findings suggest that ASD, schizophrenia, and bipolar disorder share common etiologic factors," comment lead researcher Patrick Sullivan (University of North Carolina at Chapel Hill, USA) and team.

The researchers used data from two Swedish registers (national and regional) and one Israeli conscription register to investigate rates of schizophrenia and bipolar disorder in the first-degree relatives (parents and siblings) of more than 30,000 individuals with ASDs and more than 486,000 controls.

They found that a parental history of schizophrenia was associated with a significantly increased risk for autism in both the national (odds ratio [OR]=2.9) and regional (OR=2.9) Swedish cohorts.

Similarly, having a sibling with schizophrenia was associated with an increased risk for ASDs in the Swedish national cohort (OR=2.6) and the Israeli conscription cohort (OR=12.1).

Furthermore, a parental history of bipolar disorder was associated with an increased risk for ASDs in the Swedish national (OR=1.9) and regional (OR=1.6) cohorts, and having a sibling with bipolar disorder was associated with a similarly increased risk for ASDs.

"The presence of schizophrenia or bipolar disorder in first-degree relatives was a consistent and significant risk factor for ASDs in all three samples," conclude Sullivan et al in the Archives of General Psychiatry.

They add that further research is necessary, as "the degree to which ASD and schizophrenia share etiologic factors has important implications for clinicians, researchers, and those affected by these diseases."

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