Characterized by persistent thoughts or impulses, obsessive compulsive disorder forces individuals to perform repetitive actions to try to relieve anxiety about their uncontrollable thoughts. Dogs can also suffer from this disorder and researchers say they may be able to serve as a simplified model of the human condition, after finding certain genetic links.
Publishing their results in the journal Genome Biology, the scientists say they have identified four genes associated with canine obsessive compulsive disorder (OCD), which could introduce new paths for research into human OCD, a more complex version.
The researchers say OCD affects around 1-3% of the human population, and sufferers typically repeat normal behaviors, such as hand washing, cleaning, checking or hoarding.
In dogs, these behaviors normally involve constant grooming, repeatedly chasing their own tails or shadows, and suckling or blanket sucking. Certain dog breeds are more susceptible to OCD, including Doberman pinschers, bull terriers, Shetland sheepdogs and German shepherds.
According to the team, there are existing mouse models of OCD that are initiated by manipulating certain genes, but they thought the dog version of the disorder would be a better model for the human condition since it occurs naturally and - like in humans - SSRI or clomipramine antidepressants can relieve symptoms.
Co-senior author Kerstin Lindblad-Toh, professor at Uppsala University in Sweden and the Broad Institute in Cambridge, MA, says:
"It is intriguing that the clinical presentation and treatment strategies for OCD are so similar between dogs and people. We therefore designed our study to take advantage of comparisons between the behaviour in dogs and humans."
Four gene mutations identified that are linked to OCD
Using a range of techniques, the scientists narrowed down the genome regions involved in OCD to identify four genes consistently linked to the disease in the dog breeds susceptible to OCD.
First, the team conducted a genome-wide association study (GWAS) of Doberman pinschers and then sequenced the regions of the genomes of dogs in all bull terriers, Shetland sheepdogs and German shepherds.
From this, they could identify certain "case-only genetic variants" - mutations present in at least one of the OCD dogs but not present in healthy control dogs.
After testing these variant mutations in 69 more dogs from OCD-susceptible breeds and 19 from unsusceptible breeds, they found four genes with mutations linked to OCD - CDH2, PGCP, ATXN1 and CTNNA2 - which suggests these genes may be involved in triggering the disorder.
Hyun Ji Noh, study author from the Broad Institute, says that "compulsive dogs with unfavorable mutations in these genes may have disrupted synapse formation in the OCD-implicated brain regions, in turn manifesting uncontrollable repetitive canine behaviors."
More research needed for human applications
The researchers say that although their study shows OCD dogs can be a good model for human OCD, further research is needed to evaluate whether these genes are in fact involved in the human version.
If this is the case, investigators would then need to use the findings to identify ways to improve treatments.
Elinor Karlsson, a senior author of the paper, explains:
"By finding the genetic variants that cause OCD in dogs, we hope to understand more about the underlying neural pathways. Therapies and drugs used to treat OCD today often don't work very well in dogs or in humans. If we can figure out precisely which brain circuits are disrupted in OCD patients, this could lead to more effective and targeted treatments."
Medical News Today recently reported on a study that suggested a transmissible dog cancer genome sheds light on cancer evolution for humans. The 11,000-year-old dog cancer is helping scientists understand underlying factors that drive cancer evolution in general.