Family history of schizophrenia was associated with an increased risk for autism spectrum disorder in first-degree relatives, according to recent study results. Bipolar disorder showed a similar pattern of associations, but to a lesser extent.
Patrick F. Sullivan, MD, FRANZCP, director of psychiatric genomics at the University of North Carolina at Chapel Hill School of Medicine, and colleagues conducted a case-control evaluation of histories of schizophrenia or bipolar disorder in first-degree relatives of individuals in three samples: national coverage of inpatient and outpatient admissions in Sweden, primarily outpatient autism spectrum disorder (ASD) treatment facilities limited to Stockholm County, the largest population center in Sweden, and standardized psychiatric assessments of military conscripts in Israel. For all three populations, which had extensive patient registers, the researchers used logistic regression analyses to determine the relation between family history of schizophrenia or bipolar disorder and the outcome of ASD.
The presence of schizophrenia in parents was associated with an increased risk for ASD in the Swedish national cohort (OR=2.9; 95% CI, 2.5-3.4) and the Stockholm County cohort (OR=2.9; 95% CI, 2.0-4.1). Schizophrenia in a sibling was associated with an increased risk for ASD in the Swedish national cohort (OR=2.6; 95% CI, 2.0-3.2) and the Israeli military cohort (OR=12.1; 95% CI, 4.5-32.0). The national Swedish cohort and the Stockholm County cohort both showed positive associations between bipolar disorder in parents and ASD (OR=1.9 and OR=1.6, respectively). The Israeli military cohort did not have data on bipolar disorder in parents as a risk factor for ASD.
“Family history has historically served as an important validator for definitions of psychiatric disorders,” the researchers wrote. “If ASD, schizophrenia and bipolar disorder share etiologic risk factors, it does not necessarily follow that the disorders should be lumped into an aggregate classification. However, it is tenable that these disorders are more similar phenotypically than currently appreciated, and it might prove interesting to reevaluate the degrees of demarcation between these three disorders.”
Disclosure: The researchers report no relevant financial disclosures.