OCD, also known as Obsessive-Compulsive Disorder affects more than 2 percent of the world’s population. Characterized by having uncontrollable, reoccurring thoughts, behaviors, or both that one feels the need to repeat over and over until it is done correctly. Common compulsions include excessive cleaning, organizing things in a certain way, checking on things again and again, and obsessive counting. Scientists have just identified four genes linked to OCD behaviors in people. To help identify these genes they took a unique approach: rather than just studying humans, they also looked at the biological markers found in dogs and mice.
“We were seeking ways to take advantage of information from other species in order to inform and focus the study in humans. Each additional species that we looked at gave us more information about possible factors in the brain that contribute to OCD.” says computational biologist Hyun Ji Noh from the Broad Institute of MIT and Harvard in Cambridge, Massachusetts.
Noh’s team looked at previous studies of OCD in humans and used the information to compile a list of genetic associations, and then analyzed the results of research into compulsive behavior in mice and in dogs (which is called canine compulsive disorder, CCD). The results were around 600 genes that seemed to be linked to OCD or its variants, which can cause people to obsessively check or clean items around the house, but interestingly enough it incites similar compulsive acts in animals like dogs as well.
“Dogs, it turns out, are surprisingly similar to people. They’re chasing their own tail or chewing themselves or chasing shadows like normal, but they’re doing it for hours. They literally can’t stop,” one of the researchers, geneticist Elinor Karlsson told NPR.
Using the 600 genes, Noh’s team studied 592 individuals with OCD and compared them to 560 individuals without the disorder.
“This helped them to cull the list down to just four genes expressed in the brain – called NRXN1, HTR2A, CTTNBP2, and REEP3 – which, when they undergo mutations, are significantly associated with human OCD.”
Due to the difficulty of discovering the deeper workings of OCD the condition has typically been treated through two methods, medication and psychotherapy. Noh’s team believes these newly discovered associations could provide new leads for potential treatments for OCD.
“There had been a few studies that looked for genes associated with OCD, and they found some interesting ones, but they were never able to achieve statistical significance,” Karlsson explained to NPR.
With their findings, the team can confidently assume the gene variants disrupt synapse development and interfere with neural pathways in an area of the brain (corticostriatal loop) where serotonin and glutamate signaling occurs.
There are many biological and environmental factors to consider when it comes to diagnosing OCD. So if you’ve got the mutations, it doesn’t mean that you’ll inevitably develop OCD but it does make such a diagnosis more probable, the team thinks.
“OCD is a really complicated disease. All we can say is if you have variations in these genes, you are more likely to have OCD,” Karlsson says.
The NRXN1 and REEP3 genes have also had a significant role in studies on the autism spectrum disorder. So with further research, they hope to learn more about possible causes and treatments for more than just OCD.
This piece is based on an article by Peter Dockrill for ScienceAlert.com, which can be seen here.