Inspired by observations of pet behavior, Dr Nicholas Dodman, a veterinarian and director of the animal behavior clinic at Tufts University, has invented several new approaches to treat obsessive compulsive disorder (OCD).
OCD is a very common neurological disorder characterized by repeated occurrence of anxiety-provoking thoughts that must be relieved by repetitive behavior. This behavior may appear to others as strange or extreme and alienate people, and are often very time-consuming and decrease productivity. OCD sufferers are nearly always of normal intellect and personality, and fully recognize the irrationality of their behavior, but are helpless to stop the behavior.
Early in his career, Dodman realized that human OCD rituals are very similar to normal animal behavior that has been ritualized and carried to extremes. For example, a common ritual for OCD sufferers is repetitive hand-washing, which is basically a perversion of grooming behavior, common among all animals. Another common OCD ritual is obsessive hoarding, which is a perversion of the normal gathering and storing behavior of animals. The current mainstay of OCD treatment is cognitive behavioral therapy, basically a form of psychological counseling and training which aims to acclimatize OCD sufferers to the anxious thoughts and train them to endure such thoughts without performing the rituals. However, this therapy requires extreme willpower for success. Current pharmacological treatment is mainly limited to selective serotonin reuptake inhibitors (SSRIs), which often do not work.
Dodman had animal patients which also suffered from OCD, such as pet cats that lick their paws constantly, or dogs that chased their tails for hours. Obviously, cognitive behavioral therapy is not available to animals, and when SSRIs failed, Dodman was forced to experiment with other neurological drugs.
One of the first classes of drugs he tried were glutamate receptor blockers, including dextromethorphan (a common ingredient in cough medicine), and memantine, both of which are NMDA receptor blockers. He found that memantine, when combined with fluoxetine (an SSRI better known as Prozac), effectively prevented compulsive scratching behavior in mice. Based on Dodman’s initial animal work, a group of doctors at McLean Hospital has performed a small preliminary trial of memantine in human OCD sufferers, and found that memantine is effective in human patients .
Dodman has continued his animal OCD work, and has recently compared the genomes of Doberman dogs which displayed compulsive blanket/fur sucking behavior with normal Dobermans. He found that Dobermans which suffered from OCD has a different version of the cadherin-2 gene compared to normal Dobermans, according to his paper: A Canine Chromosome 7 Locus Confers Compulsive Disorder Susceptibility published on Nature. Cadherin-2 is a gene involved in neuronal synapse formation and stability, and different versions of cadherin-2 may cause certain neurological circuits to be strengthened or weakened, and may result in neurological symptoms. Scientists have now begun to study the cadherin-2 gene of human OCD patients to see if similar alterations are present. While there are no current drugs that target the cadherin-2 gene, the hope is that if this gene is proven to be a valid player in OCD, pharmaceutical companies will rapidly develop new drugs against this gene. Further work with animals suffering from OCD will no doubt lead to new better treatment options for human OCD patients.