The Dogs Must Be Crazy
Can animals get OCD? A leading Massachusetts veterinarian says yes—and his work might hold the key to understanding human obsessive-compulsive disorders as well.
At the same time Jenike was conducting his research, Dodman was at work on two collaborations with leading experts in human psychiatric disorders, one focused on genetics and the other on brain structure. Among the geneticists who teamed up with Dodman was Edward Ginns, the director of the Molecular Diagnostics Laboratory at the University of Massachusetts Medical School, in Worcester. Ginns was studying schizophrenia, bipolar disorder, and other mental health problems in highly isolated communities, such as the Amish. It had been easy for Ginns to find subjects when he was working at the National Institute of Mental Health in Maryland, just a couple of hours away from the genetically isolated communities he’d focused his research on. But in Worcester, there was no comparable group. There were, however, plenty of purebred dogs with mental health issues. When Ginns read about Dodman’s work, he was struck by the collaborative potential and invited him out to UMass to discuss their common research interests.
“It was a natural click,” Ginns told me. “And over the last 10 years we’ve learned to speak each other’s languages. He’s picked up the genetics, and I’ve learned the complexities of how these illnesses present in dogs.” They scoured the DNA of about 160 Doberman pinschers, both normal dogs and compulsive ones—in this case, blanket suckers who sometimes sucked so hard that they risked choking to death, as well as those who sucked on their bodies. On the seventh canine chromosome, the team found a tiny mutation in a gene that codes for a protein called neural cadherin, which is known primarily for helping neurons form connections for learning and memory and, as it happens, regulating glutamate receptors.
Confident that they’d found a genetic marker, the team looked for the same mutations in DNA samples from people with OCD and Tourette’s syndrome, a related disorder. Their results, published in early 2013, were mixed. While one of the genetic markers was found only in people with mental disorders, it was so rare overall that, statistically speaking, the finding was inconclusive. It was disappointing, but not devastating. Ginns and Dodman remain convinced that glutamate is a key to one day unlocking the causes of OCD, and have resolved to keep looking for a genetic connection as well. “If we can find the genetic signposts that are risk factors for these disorders…those all become new drug targets,” Ginns said. And as it happens, the team believes that it has found another suspect gene in compulsive dogs. This one codes for a protein that affects serotonin, but Ginns wouldn’t say much more about it because the results haven’t yet been published.
Meanwhile, Dodman has found another dog-human connection. By peering into the brains of compulsive Dobermans in collaboration with Marc Kaufman, a psychiatrist at McLean Hospital, he discovered structural brain abnormalities that mirrored those previously found in humans with OCD. The brains of compulsive Dobermans and humans, the researchers found, had more gray matter in areas associated with performing well-rehearsed tasks, as well as in one region that’s critical for communication between the brain’s two hemispheres. The gray matter was also denser in these areas.
Their work was published this year, and Dodman and Kaufman hope to begin scanning dogs over their lifetimes to track how the brain develops in canines that exhibit compulsive tendencies. “That’s something we can’t do in humans,” Kaufman said. “People live with these disorders for a decade before they’re diagnosed, and we can’t turn the clock back to see what happened in that person’s brain.”
Despite these promising results, there are plenty of skeptics. Among them is Judith Rapoport, whoselandmark 1992 study of Prozac-treated dogs, subtitled An Animal Model of Obsessive-Compulsive Disorder, had been so inspirational to Dodman. Rapoport doesn’t dispute the discoveries of Dodman and his team, but says that other promising animal treatments have not lived up to the hype when tested on humans. “In theory, it’s wonderful,” Rapoport said of animal models, but she’s lost faith, “because in psychiatry they haven’t paid off.”
That may be true, but not all animal models are created equal, said the geneticist (and Dodman collaborator) Mark Neff, the director of the program for canine health and performance at the Van Andel Research Institute, in Grand Rapids, Michigan. Mice, for instance, are often genetically modified to exhibit a desired behavior. But dogs with naturally occurring compulsive disorders “let biology tell us what’s important,” Neff explained.
Dodman has encountered plenty of skepticism from funding agencies and researchers outside the veterinary field as well. He’s heard from some psychiatrists that dogs can teach us nothing about the intricacies of the human mind. He recalls one member of a panel reviewing grant applications for Boston’s International OCD Foundation defiantly promising to “blackball” any proposals for the study of compulsive dogs.
Thomas Insel, director of the National Institute of Mental Health, expressed his doubts in a recent Science article on Dodman’s work, saying animal models of mental illness “capture, at best, only a fraction of the human syndrome.”
Some think the idea that dogs have mental disorders at all is, in a word, crazy. How deep could the mental connections be between dogs and humans, after all? One builds space stations, forms governments, tells jokes, and reads poetry. The other drinks from the toilet.
The next step for Dodman and his collaborators is to get a major grant to wrap the research involving genetics, environmental influences, brain changes, and drug therapies into one massive long-term dog study. That would allow his team to follow a large number of puppies over several years, looking for connections among their DNA, brain development, and responses to drug, dietary, or behavioral treatments. The ultimate goal would be a diagnostic test—perhaps incorporating some combination of genetic and other biological markers—that could tell us which dogs are at high risk for developing a disorder, combined with effective early interventions. If Dodman is right, and dog brains and human brains really do go haywire in the same way, these discoveries could be readily adapted for human OCD.
Dodman’s first proposal for such a study was summarily rejected by the NIH. Dodman said they’ll try again soon. After so many years, he knows nothing comes easy, especially for a veterinarian treading on what some consider human turf. “There are a lot of heavy-duty people who really believe in what we’re doing, but there are still some naysayers out there. You know, flat-earthers,” Dodman said.
“Vets are used to it, honestly,” added Dodman’s wife, Linda Breitman, herself a fellow veterinarian. “Nick’s kind of an intellectual sponge. I think people get walled in by their preconceptions, but he doesn’t.”
Jenike, of McLean’s OCD Institute, told me that, for humans, the one-two punch of a diagnostic test for OCD paired with early interventions “would be as good as a cure.” But he’s still not sure whether dogs can show us the way. “These behavior problems in humans are so complicated,” he said. “Whether [dog models] will turn out to be dramatically helpful, I just don’t know.”
In the meantime, desperate owners keep showing up at Dodman’s clinic, which he jokingly calls “last-resort nation.” Dodman sent Ryeko and his owners off with a Prozac prescription and pamphlets about compulsive behaviors and treatment tips. The couple took Ryeko on a final walk around the woody North Grafton campus before making the long trip home.
Dodman believes that the compulsive behaviors of dogs are likely triggered by the stresses of a modern pet’s life, including loneliness, confinement, and boredom. In that way, his research may hint at even more profound connections between humans and the four-legged creatures we love, sometimes too much. As Dodman said, “Biologically speaking, we’re all animals in this world together.”
November 7, 2013: Due to a reporting error, the origin of research into horse-cribbing behavior by Nicholas Dodman and Louis Shuster was mischaracterized. The link between cribbing and opioids did not stem from something Shuster read. Rather, Dodman suggested the opioid theory to Shuster based on observations from a separate study of morphine on horses they had undertaken together. He and Shuster then tested and found evidence to support this association.