Cohort profile: Epidemiology and Genetics of Obsessive-compulsive disorder and chronic tic disorders in Sweden (EGOS).

PURPOSE: The EGOS study (Epidemiology and Genetics of Obsessive-compulsive disorder and chronic tic disorders in Sweden) is a large-scale, epidemiological, prospective cohort that is used to identify genetic and environmental risk factors in the etiology of obsessive-compulsive disorder (OCD) and chronic tic disorders (CTD). METHODS: Individuals born between January 1954 and December 1998 with at least two diagnoses of OCD or CTD at different timepoints in the National Patient Register (NPR), and followed between January 1997 and December 2012, represent the EGOS source population (n = 20,374). The Swedish Multi-Generation Registry (MGR) are then used to define family relatedness for all cases and additional phenotypic and demographic data added to the resultant database. To create an epidemiologically valid subset of the source cohort that also includes biospecimens and additional phenotyping, we contact cases from within the source population. To date, 6832 invitations have been sent out and 1853 (27%) have elected to participate in the EGOS biospecimen collection. RESULTS: To date, 1608 biological samples have been collected, of which 1249 are genotyped and 832 supplementary Obsessive-Compulsive Inventory-Revised (OCI-R) and/or Florida Obsessive-Compulsive Inventory (FOCI) have been completed by individuals with OCD and/or CTD, age 16-64 years. DNA samples are genotyped using Infinium Global Screening Array and will undergo whole-exome sequencing in the future. Detailed information is available for each individual through linkage to the Swedish national registers, e.g., identification of additional psychiatric diagnoses, medical diagnoses, birth-related variables, and relevant demographic and social data. CONCLUSION: EGOS benefits from a genetically homogeneous sample with epidemiological ascertainment, minimizing the risk of confounding due to population stratification on ascertainment bias. In addition, this study is built upon clinical diagnoses of OCD and CTD in specialized psychiatric care, which reduces further biases and case misclassification.

Identification of common genetic risk variants for autism spectrum disorder.

Autism spectrum disorder (ASD) is a highly heritable and heterogeneous group of neurodevelopmental phenotypes diagnosed in more than 1% of children. Common genetic variants contribute substantially to ASD susceptibility, but to date no individual variants have been robustly associated with ASD. With a marked sample-size increase from a unique Danish population resource, we report a genome-wide association meta-analysis of 18,381 individuals with ASD and 27,969 controls that identified five genome-wide-significant loci. Leveraging GWAS results from three phenotypes with significantly overlapping genetic architectures (schizophrenia, major depression, and educational attainment), we identified seven additional loci shared with other traits at equally strict significance levels. Dissecting the polygenic architecture, we found both quantitative and qualitative polygenic heterogeneity across ASD subtypes. These results highlight biological insights, particularly relating to neuronal function and corticogenesis, and establish that GWAS performed at scale will be much more productive in the near term in ASD.