Obsessive-compulsive disorder in dogs and cats appears to be a genetic trait more common among certain breeds, and researchers find that only about one in ten dogs with OCD comes from an animal shelter

© L. Pelaez Chewing is part of puppies’ normal behavior, but in older dogs, excessive chewing may indicate obsessive-compulsive disorder.

Inbreeding has been blamed for countless problems in dogs and cats, from hip dysplasia to reduced fertility. Researchers at the University of Pennsylvania believe that obsessive-compulsive disorder might be the next affliction to add to the list. Among its findings, their recent study investigating obsessive-compulsive disorder (OCD) in dogs and cats concluded that selective breeding and inbreeding may play a large role in the disorder’s occurrence among companion animals.

The study, published in the Journal of the American Veterinary Medical Association (Vol. 221, No. 10), can help shed some light on several issues: factors that may lead to the disorder, methods of treatment, and ways in which the disorder’s expression in dogs and cats compares to its appearance in humans.

From January 1989 to December 2000, dogs and cats brought to the University of Pennsylvania’s Behavior Clinic were evaluated for obsessive-compulsive disorder. Overall, researchers studied 103 dogs and 23 cats with the disorder.

Obsessive-compulsive disorder in dogs expresses itself through repetitive behaviors that include circling, tail chasing, fence-running, pacing or spinning, fabric chewing, and pica (the consumption of non-food items, such as rocks). Cats with the disorder exhibit self-mutilation, excessive grooming, tail chasing, and fabric sucking or chewing.

Most animals in the study were treated successfully with behavior modification and medication—at first, amitriptyline, and later, clomipramine (both are tricyclic antidepressants). Clinicians administered one or more of the drugs to 84 of the 103 dogs. They found clomipramine much more effective than amitriptyline, although the authors point out that OCD cannot be cured.

Some of the researchers’ findings include:

• The majority of the dogs with OCD were male (in a ratio of 2:1) while the majority of the cats were female (2:1, although in a smaller sample).
• The most prevalent dog breeds in addition to mixes were German shepherds, rottweilers, dalmatians, and bulldogs. Breed origins seemed to lead to associated behaviors; for example, herding breeds tended to chase their tails. This led researchers to believe that OCD occurrence was based on genetic factors. Among the cats, the most commonly afflicted breed was the Siamese.
• Obsessive-compulsive disorder surfaced in dogs and cats—as in humans—around adolescence. The average age for dogs at onset of the disorder was 20.3 months; cats, 28.2 months. The authors therefore recommended that young dogs and cats be screened regularly.
• The majority of dogs (almost 60 percent) came from breeders, either “backyard” or professional. Only about one in ten were adopted from animal shelters (the authors did not categorize these dogs by their original source).
• Many of the animals studied (74.8 percent of the dogs and 39.1 percent of the cats) had other behavioral issues, such as separation anxiety or attention-seeking behavior.
• Dogs—like humans—may realize that their actions are out of the ordinary, and will attempt to perform their compulsive behavior in private. In addition, other cats and dogs in the household (or, it can be inferred, in the shelter) will try to avoid the OCD-afflicted animals because of their behavior.
• Conditions that were stressful for the animals increased expression of obsessive-compulsive behavior.

Obsessive-compulsive disorder is generally associated with humans, but the authors’ findings indicate a surprising possibility: “It is important to realize that the development of specific animal breeds and the practice of inbreeding within those breeds suggest that the prevalence of OCD in dogs could be higher than that reported for humans.”