NEW YORK (Reuters Health) - A new study adds to evidence that pregnancy may worsen or bring on symptoms of obsessive-compulsive disorder in some women -- suggesting, researchers say, that certain cases of the disorder involve abnormal responses to hormonal changes.

Obsessive-compulsive disorder, or OCD, is an anxiety disorder in which people have persistent, unwanted thoughts that compel them to repeat routines and rituals over and over. An obsession with germs or cleanliness, for example, may drive a person to wash his or her hands constantly throughout the day.

It’s estimated that just over 2 million U.S. adults have OCD, with the symptoms often arising in childhood or the teenage years.

However, a few studies have found that OCD can also arise during or soon after pregnancy, and that pregnancy may worsen OCD symptoms in some women who already have the disorder.

The new study confirms and extends those findings, according to lead researcher Dr. Ariadna Forray, of Yale University School of Medicine in New Haven, Connecticut.

Using medical records and interviews with 126 women treated at the Yale OCD Clinic, the researchers found that of the 78 women who had ever been pregnant, 24 (32 percent) had their first OCD symptoms during or soon after pregnancy.

And when the researchers looked at pregnancies among women with pre-existing OCD, they found that the women’s OCD symptoms worsened one-third of the time. (In a smaller number of pregnancies -- 22 percent -- symptoms actually improved.)

Forray’s team also found that women whose pre-pregnancy OCD typically got worse in the premenstrual period were at greater risk of exacerbations during pregnancy. That finding, the researchers say, supports the notion that there is a “hormone-related” subtype of OCD that affects some women.

“These women may have a differential sensitivity to reproductive hormones, and, as such, normal reproductive events are triggers for the onset or exacerbation of OCD,” Forray told Reuters Health in an email.

It is not known why such differences in hormone sensitivity may exist, she said, but it could involve differences in genes that help regulate, or are regulated by, reproductive hormones.

Forray said the findings suggest that women with OCD, and their doctors, should be aware that pregnancy might worsen their symptoms -- particularly if they normally have exacerbations in the premenstrual period. They and their doctors can then keep track of their OCD symptoms during pregnancy and possibly make changes in how they are managing the disorder.

The standard treatments for OCD include cognitive-behavioral therapy, antidepressants and anti-anxiety medications.

Women and doctors should also be aware that OCD can arise during or soon after pregnancy, according to Forray.

It is normal for expectant or new mothers to have some anxiety and worries. But, Forray said, if certain thoughts and behaviors -- like worries about cleanliness, order, or the baby’s well-being -- start to cause distress and interfere with everyday functioning, then it is time to discuss it with your doctor.

The current findings also suggest that women who develop OCD around the time of pregnancy may be particularly likely to have symptoms related to fear of “contamination” -- germs and dirt.

Of women whose symptoms arose during or after pregnancy, 67 percent had such worries. That compared with 36 percent of women whose OCD onset was not pregnancy-related.

SOURCE: link.reuters.com/nuw39k

Journal of Clinical Psychiatry, online May 18, 2010.