Researchers have laid to rest the myth that another mental disorder stems from "bad parenting." A new study from Johns Hopkins has shown that obsessive-compulsive disorder, like schizophrenia and bipolar disorder, tends to run in families and has a strong genetic basis.
People with a first-degree relative with OCD--brothers, sisters, parents--have a five times greater risk of having the illness themselves at some time in their lives, according to results of the study published in the April Archives of General Psychiatry.
The researchers identified 80 patients with OCD and 343 of their first-degree relatives and compared them with 73 control patients without mental illness and 300 of their relatives. The results showed the strong familial link for the most common form of the disorder, which strikes in childhood.
Marked by persistent, intrusive, senseless thoughts (obsessions) and repetitive behaviors that can't be ignored (compulsions), OCD has been called one of the 10 most disabling medical conditions worldwide by the World Health Organization. It also has long evaded psychiatrists' attempts to show that genes play a role in who gets the disorder. "We've known OCD as a psychiatric condition for more than a century," says psychiatrist Gerald Nestadt, who led the research team. "But doubts have remained about the hereditary nature."
"There is surely some environmental aspect to OCD," Nestadt says. "If your mother is constantly washing her hands and worrying over it, that could have an effect. But what's obvious to investigators is that, in patients with affected family members, their behavior isn't necessarily the same as the family member's. A patient whose mother washed her hands might, for example, have to check light switches over and over. They both have an obsession, but their behavior is different. And that points to a biological basis.
Psychiatric studies where researchers must evaluate large numbers of people often suffer from the common bugaboo of unintentional bias, Nestadt says. This may be a reason behind inconclusive results of earlier studies that tried to link heredity and OCD. This current research, he says, used patients from different clinics to avoid institutional bias. Diagnosing researchers were blinded as to a patient's condition.
The study opens the door to the next step, identifying the actual gene or genes involved, Nestadt says.
OCD affects as high as 3 percent of the world's population. Although it touches all ages, the period of greatest risk is from childhood to middle age. Twin studies have shown identical twins have a higher instance of OCD--almost 90 percent--than fraternal twins, where the odds of both having the disorder is close to 50 percent.
The study was funded by NIH grants. Other researchers are Jack Samuels, Mark Riddle, O. Joseph Bienvenu III, Kung-Yee Liang, Michele LaBuda, John Walkup, Marco Grados and Rudolph Hoehn-Saric.