Obsessive-compulsive disorder (OCD) is a complex and often debilitating condition that affects up to three percent of people, but the biological basis of the disorder has remained largely elusive. While we’ve known that genetics play a role, previous genetic studies have been limited by their relatively small sample size and have only identified a few of the specific genetic variants involved.
But that is now changing.
In a recent study, the largest of its kind ever conducted for OCD, researchers identified dozens of genetic variants associated with the disorder, offering unprecedented insight into its underlying biology.
The Power of Numbers
For complex conditions like OCD, genetic discovery is a numbers game. To find the subtle genetic variations that contribute to risk, scientists need to compare the DNA of vast numbers of people with and without the condition. This is where the research model of the 23andMe Research Institute makes a world of difference.
This study combined data from 28 different cohorts. The result was a dataset of incredible scale, including 53,660 individuals with OCD and more than 2 million controls. Consented 23andMe research participants made up about half of the entire cohort in this study. This immense contribution, made possible by those who choose to participate in research, was critical to achieving the statistical power needed to make these new discoveries.
What the Study Found
By scanning the genomes of millions of individuals, the researchers identified 30 independent genetic variants that were significantly associated with OCD. Of these 30 genetic variants, half are entirely new discoveries, while the others confirm and strengthen findings from previous, smaller studies. Researchers mapped these genetic variants to 25 genes that are likely impacted by those variants.
Zeroing In on the Brain
Identifying the genes is just the first step. The next question is: where in the body do these genes do their work?
To find out, the researchers performed tissue and single-cell enrichment analyses. The results were striking. The genetic signals for OCD were highly enriched in six different types of human brain tissue. In contrast, there was no enrichment found in tissues outside the brain.
The study drilled down even further, pinpointing specific cell types and found that these genes are at work in the same cells identified by neuroimaging and deep brain stimulation studies of OCD. By independently identifying these precise brain regions and cell types through genetics, this study provides additional supporting evidence that these genes and neurons play a direct role in the biology of OCD.
Shared Genetics
The study also investigated the genetic relationship between OCD and other psychiatric and behavioral conditions. The researchers found statistically significant positive genetic correlations between OCD and a range of other disorders, including anxiety, depression, anorexia nervosa, and Tourette syndrome
This finding reinforces a growing body of evidence that many psychiatric conditions, while appearing different on the surface, are likely to share some underlying genetic susceptibility factors. Understanding this genetic overlap may be key to understanding mental health as a whole.
A Foundation for the Future
This study represents a pivotal moment for OCD research. By dramatically expanding the list of known genetic variants associated with OCD and grounding them in the specific biology of the brain, this work opens doors for researchers to explore the precise mechanisms by which these genes influence brain circuits and contribute to OCD symptoms.
Ultimately, these findings may be a critical step toward developing novel and more effective treatments for a disorder that has long been misunderstood.
And once again, we want to extend our deepest gratitude to 23andMe research participants. Your contribution to this landmark study has advanced our understanding of OCD and paved the way for a healthier future.
