People with OCD are driven to repeat rituals Jeffrey Hamilton/Getty

Four genes have been identified that are linked to obsessive compulsive disorder (OCD). The genes all play a role in the same brain circuit, and may help explain why people are more likely to have OCD if they have a relative with the condition.

People with OCD have intrusive thoughts and feel driven to repeat rituals, such as handwashing, to relieve their anxiety. To investigate if OCD has a genetic basis, Hyun Ji Noh at the Broad Institute of MIT and Harvard and her colleagues compared more than 600 genes across 592 people with OCD, and 560 people who don’t have it.

They chose these candidate genes from several lines of evidence. Of these genes, 222 had been linked to compulsive grooming in mice, and 196 had been linked to autism in people – a condition that can involve repetitive behaviours.


The team also looked at 56 genes that they had identified in a study of dogs with canine compulsive disorder, a condition in which dogs repeatedly chase their tails, pace back and forth, groom themselves or sucks things, sometimes for hours at a time.

Brain safety circuit

The analysis identified four genes that are different in people who have OCD. All four of these are active in a brain circuit that links the striatum, thalamus and cortex regions.

The striatum is involved in learning and relays messages via the thalamus to the cortex, where decisions are made. In people with OCD, the information passing around this loop can become corrupted. Previous research suggests this makes it harder to tell when a situation is safe or risky.

The finding adds to evidence that the disorder has a genetic component, says Jessica Grisham at the University of New South Wales in Australia. “We know you’re four times more likely to develop OCD if you have a first-degree relative with the disorder,” she says.

That doesn’t mean you will necessarily get OCD if your parents have it. “There’s a complex interaction between genes and environment,” says Grisham. OCD can arise in people without a known family history, sometimes after a traumatic event, she says.

Better treatments

One of the genes identified in the analysis – HTR2A – is also involved in serotonin signalling. This hints that people with OCD may have problems regulating serotonin in their brains, says Noh.

If so, this may explain why up to 60 per cent of people with OCD benefit from taking SSRI antidepressants, which boost the amount of serotonin in the brain. About half of dogs with compulsive disorder also respond to SSRIs.

Understanding how the genetic variants affect OCD will hopefully lead to better treatments, says Noh. “We would like to develop a drug that reverses the effects, either by targeting the gene itself or the pathway it regulates,” she says.

Journal reference: Nature Communications, DOI: 10.1038/s41467-017-00831-x

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