Abstract
Obsessive-compulsive disorder (OCD) affects ~1% of children and adults and is partly caused by genetic factors. We conducted a genome-wide association study (GWAS) meta-analysis combining 53,660 OCD cases and 2,044,417 controls and identified 30 independent genome-wide significant loci. Gene-based approaches identified 249 potential effector genes for OCD, with 25 of these classified as the most likely causal candidates, including WDR6, DALRD3, CTNND1 and multiple genes in the MHC region. We estimated that ~11,500 genetic variants explained 90% of OCD genetic heritability. OCD genetic risk was associated with excitatory neurons in the hippocampus and cortex, along with D1- and D2-type dopamine receptor-containing medium spiny neurons. OCD genetic risk was shared with 65 of 112 additional phenotypes, including all of the psychiatric disorders we examined. In particular, OCD shared genetic risk with anxiety, depression, anorexia nervosa, and Tourette syndrome, and was negatively associated with inflammatory bowel diseases, educational attainment, and body mass index.