Obsessive Compulsive Disorder can appear from afar like a slapstick comedy routine, except the script never ends and the sufferer is left metaphorically if not literally chasing his tail. It is one of those disorders that dogs and humans share, although in dogs Obsessive Compulsive Disorder becomes Canine Compulsive Disorder because of the belief of some scientists at the time of naming and even now that dogs cannot have thoughts even repetitive ones!
In humans, obsessive compulsive behaviors tend to relate to checking, collecting, and ordering, while in dogs, they tend to involve acts associated with predation, locomotion, and feeding. Specifically, they include repetitive actions like tail chasing, flank sucking, and pacing, which tend to show up in specific breeds. Bull terriers and German shepherds are well known tail chasers. Doberman pinschers are the poster dogs for flank sucking. Other animals appear to engage in obsessive-compulsive behavior, but I will stick to dogs.
That clustering by breed along with their well documented pedigrees makes purebred dogs ideal subjects, many geneticists argue, for looking for possible genetic roots of OCD. In 2010, Dr. Nicholas Dodman, director of the animal behavior clinic at the Tufts University Cummings School of Veterinary Medicine and a pioneer in the study of OCD in dogs, and his colleagues identified a variant version of a cadherin 2 gene responsible for producing a protein of the same name that is involved in brain development. The variant gene appeared far more frequently in flank-sucking Dobermans than in normal ones.
The findings of Dodman and his colleagues, which I covered for The New York Times, January 19, 2010, provided the most solid link yet between a particular behavior, a protein, and the gene that made it in dogs. Linking behavior to genetics is the primary goal of many canine geneticists.
But genes are nothing if not twisted, subject to the vagaries of environment, diet, living circumstances, exposure to chemicals or foods that trigger some reaction. Somehow all of those elements and more go into shaping who an animal is and becomes. That means that just because an individual might have a genetic variant that has been associated with a particular condition does not mean that it will suffer from that condition and the obverse is also true.
A team of Finnish, French, and Canadian researchers reveals the complex interplay of genes, personal history, and environment in a study of tail chasing in a recent issue of the journal PLoS One. The group studied 368 dogs from four breeds of well known tail chasers—Finnish bull terriers and miniature bull terriers, German shepherd dogs, and Finnish Staffordshire bull terriers.
It is an exhaustive study looking at everything from age of onset of tail chasing—three to six months in bull terriers and German shepherds; six to twenty-four months in miniature bull terriers and Staffordshire bull terriers—to the frequency of other compulsive behaviors along with tail chasing, like repetitive freezing, pacing, or trancelike behavior.
The paper, “Environmental Effects on Compulsive Tail Chasing in Dogs,” contains some surprising results. Other findings provide strong confirmation for what was already known or suspected.
The results are presented breed by breed and in aggregate. Taken together, for example, they suggest that tail chasers were short-changed when it came to maternal care, having been taken on average from their mothers at seven rather than the customary eight weeks. That finding seems potentially very interesting in light of a growing interest in socializing puppies from the day they are born.
Tail chasers appeared to lack or to need more of certain nutrients and micronutrients, particularly vitamin B6 and vitamin C, which seem to curb tail chasing. If confirmed, this finding could have a major effect of the use of serotonin reuptake inhibitors to tail chasing and perhaps other obsessive compulsive behaviors in dogs.
Tail chasers tended to have multiple obsessive behaviors, including repetitive pacing and “trancelike freezing,” which seemed most common in bull terriers. More than half of the tail chasers tended to respond poorly or not at all to their human companions while pursuing their obsession. German shepherd and bull terrier tail chasers tended to be more noise phobic and shyer around people than non-tail chasers. Neutered females were less inclined to chase their tails, leading the researchers to speculate on the involvement of ovarian hormones in tail chasing.
The researchers did not find boredom a significant cause of tail chasing, although the presence of children and/or other dogs in the house served to reduce tail chasing.
Lead author Katriina Tiira from the University of Helsinki also reported that the team had not found any clear genetic link to tail chasing. The genetic locus for cadherin 2 associated with flank sucking in Doberman pinschers is apparently not involved in tail chasing. Other prospects came to nothing.
The researchers expect to find a genetic link somewhere. For now they have shown the power of non-genetic factors on a dog’s development.
They invoke the dog as a fine model for humans, but there is little evidence that the model has helped do more than show us a small part of the vast amount we don’t know about dogs. More studies about dogs and dogs and people are what we need.