The Dogs Must Be Crazy

Researchers estimate that two to three million American adults and half a million children have some type of obsessive-compulsive disorder, characterized by behaviors ranging from excessive hand-washing to constant hair-plucking. The affliction has penetrated popular culture, of course, as we now have reality shows dedicated to obsessive hoarders and even the series Monk, which features a detective whose compulsive attention to cleanliness, ritual, and excruciating detail helps him solve murder mysteries.

In real life, OCD is debilitating. Sufferers are tortured by their worries and trapped in a never-ending cycleof checking, grooming, or hoarding.They live in constant fear and become slaves to their compulsions. The behavior wrecks marriages and careers. Unlike those suffering from psychotic disorders, people with OCD are not delusional. They’re well aware of reality and are terrified by their abnormal and intrusive thoughts and behaviors. Major depression is common, and according to recent studies, as many as 15 percent of people suffering from OCD have attempted suicide, and about half have considered it.

When Dodman opened his animal-behavior clinic in the 1980s, human OCD research was just emerging from Sigmund Freud’s shadow. Throughout most of the 20th century, psychologists believed that compulsive behaviors were fueled by neuroses rather than neurochemistry. Scientists now agree that both genetic and environmental factors are to blame, but the actual causes and pathology of the disease continue to elude them. The biggest roadblock in human OCD research is the fact that patients usually seek help only when their symptoms become too severe to hide. This means that researchers aren’t privy to how OCD develops in the brain, since all of their subjects already have the full-blown illness. Without this data, researchers can’t pinpoint what kinds of events or neurochemical changes trigger OCD. Without blood tests or other ways of diagnosing or assessing a person’s risk, the best doctors can hope for is a treatment, rather than a cure.

Dogs, however, offer researchers many more subjects for observation and study. That’s because 20 to 30 percent of certain breeds show symptoms of compulsive disorders, an order of magnitude more frequent than in people. This is important because, from a certain perspective, the strange behavioral patterns exhibited by the affected dogs can be interpreted as surprisingly human. Dodman told me about a Doberman habit called “shopping” in which the dogs ritually collect things like shoes or stuffed animals from all over the house. “It’s just like hoarding!” Dodman says.

In a 2011 study, meanwhile, Dodman and Alice Moon-Fanelli, an animal behaviorist who was then at Tufts, observed tail-chasing in bull terriers that looked a lot like autism, a disorder that often coincides with OCD. A bull terrier in spin mode seems to be in its own world, and may even lash out at anyone who interrupts. When not spinning, the dogs sometimes lapse into “trance-like staring,” and may become “withdrawn, and abnormally preoccupied with objects, such as ballsor sticks.”

In both humans and dogs there appears to be a genetic link to compulsive behavior disorders as well. OCD tends to run in families, while most canine sufferers are purebreds. Compulsive behaviors are even breed-specific. Labradors, for instance, lick their forelegs raw, while Doberman pinschers suck their own bodies raw and suck holes in blankets, King Charles spaniels stalk shadows and snap at imaginary flies, and bull terriers and German shepherds chase their tails like dervishes.

The more dogs that Dodman saw in his clinic, the more he was convinced of the truth of his compulsive-disorder diagnosis. Other researchers were observing this as well. In 1992, Judith Rapoport, a leading OCD researcher at the National Institutes of Health, published a study showing that Prozac, developed for treating human depression, helped ease compulsive behavior in dogs. Rapoport’s findings were the first ammunition against the folks Dodman calls, “those naysayers who think human beings have this special unique position at the center of the universe.”

Dodman considered the link between Rapoport’s study and his own. Serotonin drugs, along with the opioid blockers that he and Shuster first tried, had calmed the compulsions, but neither was a cure-all. Puzzling over the connection between opioid blockers and serotonin enhancers, Dodman and Shuster eventually zeroed in on a third brain chemical: glutamate.

Glutamate is known to excite whatever synapse it touches, earning it a reputation as the brain’s “go signal.” The opioid blockers Dodman and Shuster had originally used to treat cribbing horses blocked glutamate receptors. Drugs like Prozac also turned down the brain’s glutamate production. Was it possible, they asked, that glutamate had been the culprit all along? To test the idea, they tried the glutamate-blocking drug memantine on various compulsive animals. It worked on mice that had been genetically engineered to groom themselves bare. It worked on cribbing horses. It worked on compulsive dogs, too. In addition, Dodman demonstrated that combining memantine and Prozac was more effective than either drug alone.

Dodman published the dog study in 2009, and almost immediately, Michael Jenike, the medical director of the OCD Institute at McLean Hospital, reached out to him. Dodman had been invited to speak at the institute a few years earlier, and at the time, Jenike had had doubts about his animal models. “I remember being somewhat skeptical, and I still am,” Jenike told me. “With OCD, you have to know what the person’s thinking, and you can’t really know what’s going on in an animal’s head.”

Nevertheless, inspired by Dodman’s work on animals, Jenike decided to try memantine on a couple dozen of his patients who weren’t responding well to standard treatments. He found that the drug worked in people, too.

“That was a ‘wow’ moment,” Dodman said. It didn’t prove that a dog’s tail-chasing and a man’s hand-washing were caused by the same mental misfires, but, pharmaceutically at least, there seemed to be a connection.