The clinical and etiological relationship between autism spectrum disorder (ASD), schizophrenia, and bipolar disorder is not clear. The extent to which they share causal bases has important implications for clinicians, researchers, and for the people suffering from these disorders. To determine whether a family history of schizophrenia and / or bipolar disorder represents a risk factor for the development of ASD, researchers from the Department of Genetics at the University of North Carolina compared the presence of these disorders in first-degree relatives of groups of people with and without ASD, in the areas of Stockholm and a representative sample of the general population of Sweden, as well as Israel. The presence of schizophrenia in parents was associated with an increased risk of ASD in the Swedish national cohort [odds ratio (OR) 2.9, 95% CI, 2.5-3.4] in the sample and the County of Stockholm (OR, 2.9; 95% CI, 2.0-4.1). The presence of schizophrenia in a first-degree relative was associated with an increased risk of ASD in both the Swedish national cohort (OR 2.6, 95% CI, 2.0-3.2) and in the Israel conscription cohort (OR , 12.1, 95% CI, 4.5-32.0). Bipolar disorder showed a pattern of associations similar to schizophrenia, but with a lower statistical strength. The results of this study, conducted on 3 different registers, confirm those of a similar study conducted in Denmark in 2005 and suggest that ASD, schizophrenia, and bipolar disorder share some common etiological factors. In recent years CREA has repeatedly dealt with the growing findings of genetic alterations common to all three groups and other neurodevelopmental disorders, including intellectual disabilities. The recent implementation of next-generation sequencing technologies and the creation of large consortia have confirmed alterations in gene expression regulation, synaptic architecture and immunity. These diverse pathways seem to converge in aberrant synaptic plasticity and remodelling, which leads to altered connectivity between relevant brain regions.
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