November 21, 2012
Since a publication by child psychiatrist Dr. Judith Rapoport, et al, in the Archives of General Psychiatry (1992), the term “compulsive disorder” has entered the veterinary lexicon. Before that, repetitive disorders of species were referred to as “stereotypies.”
I’ve studied such behavior for nearly 30 years, the first 10 of which I believed I was studying stereotypies.
My first observations were in horses engaging in “stall vices” like cribbing and weaving and stall walking. Later, I broadened my interest to include acral lick dermatitis and tail chasing in dogs and wool-sucking/pica and psychogenic alopecia in cats. I also had some interest in feather-picking in birds, chain chewing and bar biting in pigs and the plethora of repetitive disorders shown by zoo animals.
I always believed the mechanism underlying these behaviors was essentially the same with, perhaps, certain species variations imposed on a common underlying theme.
Early on, I was convinced that stereotypies were mediated by nature’s own morphine-like substances, the endorphins, as morphine antagonists blocked the behaviors I studied in horses and dogs. Dr. Rapoport’s 1992 article, however, changed the way we think about repetitive disorders and altered our approach to treatment.
Rapoport showed that acral lick dermatitis in dogs responded to selective serotonin reuptake inhibitors (SSRIs) like Prozac and Zoloft to the same extent and over the same time course as human obsessive compulsive disorder patients. For the rest of that decade, Rapoport promoted the concept of acral lick dermatitis as a model of human obsessive compulsive disorder.
Veterinary behaviorists quickly extended the concept to include pretty much all behaviors formerly labeled stereotypies in animals. Behavior after behavior confirmed the OCD concept by responding affirmatively to treatment with anti-compulsive medication. Not only did dogs with ALD respond to SSRIs but so did tail chasing and shadow chasing.
Cats with wool-sucking/pica or psychogenic alopecia also responded well to these medications, as did feather picking in birds, cribbing in horses, bar biting and chain chewing in pigs, and an assortment of compulsive behaviors in zoo animals.
In people with OCD—and by inference in animals exhibiting compulsive behavior—the cycle goes something like this: Anxiety leads to engagement in a repetitive behavior (a compulsion), which affords temporary relief. Later a constantly recurring thought (an obsession) occurs that causes escalating anxiety. Engagement in the compulsion relieves the anxiety, and so the cycle is propagated.
It is impossible to prove that animals obsess but that doesn’t mean they don’t. People, especially children, sometimes have compulsions that occur without a preceding obsession, so even if animals don’t obsess that doesn’t mean they can’t have a compulsive disorder.
Animals exhibiting compulsive disorders tend to be more anxious and highly strung than their more laidback counterparts. Cribbing horses seem more actively anxious than non cribbers. Middle-aged dogs with ALD seem more anxious and vigilant than their non-compulsive peers. African grey parrots, notorious for their high-strung nature, feather pick more often than other species of psittacine birds.
The anxious nature may be inherited, along with breed- and species-typical behaviors. Having a genetic propensity for a behavior does not mean that an individual will necessarily manifest it. An environmental component, such as a situation of high conflict, seems necessary to cause one or another natural behavior to go awry and be expressed compulsively.
The particular compulsive behavior that is expressed depends on species and breed predilections and the experiences and programming of the individual. Dogs tend to develop compulsive disorders related to the natural behaviors of grooming (ALD) and predation (light/shadow chasing and tail chasing).
Cats develop compulsive disorders related to grooming (psychogenic alopecia) and consummatory behavior (wool-sucking/pica).
It is predictable that horses, who spend the majority of their time in nature grazing and ambling around, will develop consummatory and locomotor compulsions, like cribbing and weaving/stall walking, respectively.
It is predictable that pigs, who spend their days rooting around foraging engage in a compulsion like chain chewing/bar biting; and that birds, which preen their feathers as a matter of survival in the wild, end up with a compulsive disorder like feather picking.
The question is what to do about compulsive disorders? How should they be treated?
In humans there are two options: cognitive therapy and pharmacotherapy. In animals, the former is not an option so it is replaced with environmental enrichment. Environmental enrichment alone will not normally reverse a compulsive disorder, but a stress-free, user-friendly environment can prevent compulsive behavior from developing in the first place and make relapse less likely after successful pharmacological treatment.
Pharmacotherapy relies on the use of SSRIs or, more recently, drugs that block central NMDA receptors, attenuating the action of the excitatory neurotransmitter glutamate.
For those skilled in the art, a combination of SSRI and NMDA blocker can work together synergistically. Although it is popular to consider all repetitive disorders as compulsive disorders, there are still some curve-ball diagnoses out there. Some medical conditions cause behaviors resembling compulsive disorders though they are actually not.
Examples include brain tumors that may cause circling in dogs; allergic skin disease that may lead to over grooming in a cat; or partial seizures that can cause several behavioral manifestations in various species depending on the region of the brain most affected.
Medical conditions aside, veterinarians now have a much better idea about the genetics and circumstances leading to the expression of compulsive disorders in animals and, more importantly, can do something to help affected patients.
It is no longer acceptable to simply block the animal’s ability to engage in the compulsions as this approach does nothing to address the underlying issues.
Preventing compulsive behaviors by physical means, such as applying Elizabethan collars to dogs with ALD or confining weaving horses to one half of their stall by a divider, will lead to more anxiety, not less, and will not resolve the more fundamental problem of environmental stress.
Buccostomy and myectomy make no sense for treating cribbing horses; neither does tail amputation help when it comes to treating tail-chasing dogs. However, employing environmental enrichment and “occupational therapy” coupled with pharmacotherapy, allows us to treat most animal OCDs successfully, sometimes to the point of cure.
An author and researcher, Dr. Dodman is a professional at Cummings School of Veterinary Medicine at Tufts University and is founder and director of Tufts’ Animal Behavior Clinic.
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