A Mount Sinai-led study has highlighted the contributions of both rare and common variants in the risk for obsessive compulsive disorder (OCD).
Obsessive compulsive disorder (OCD) is a long-lasting psychiatric disorder. It is characterised by intrusive and unwanted thoughts, images or urges that are typically linked to ritualised acts. It affects 1-3% of the population. Several studies have provided reliable evidence for a significant genetic contribution to risk of disease. Other studies have also shown the role of environmental factors in this risk. However, the contribution of genetic variation across the allele frequency spectrum to this heritability remains unclear.
Estimating SNP-based heritability for OCD
In a recent study, published in The American Journal of Psychiatry, researchers aimed to estimate the heritability of OCD from inherited genetic variation. They also contrasted their results with those of previous studies. They specifically had a sample which consisted of 2,090 Swedish-born individuals diagnosed with OCD and 4,567 control subjects. All individuals were genotyped for common genetic variants (>400,000 single-nucleotide polymorphisms).
The team found that around 29% of the risk for OCD could be attributed to differences in SNPs between patients and control subjects. In addition, about 90% of these differences were commonly observed throughout the general population. Interestingly, the researchers also found that about 10% of the risk could be linked to rare genomic differences, which have not been previously seen in other studies. Further analysis revealed that these OCD-related SNPs were distributed across patients’ chromosomes. This suggests that multiple variants across the genome combine to influence risk.
Overall, these results indicate that OCD risk may be driven by randomly occurring changes across the entire genome rather than a few naturally selected hotspots. This study also demonstrates the important role of rare genomic differences in the risk of OCD, which may alter how scientists study the disorder and develop new treatments.
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