NEW YORK (Reuters Health) – Obesity is a well known risk factor for certain physical health problems, but a new study suggests that heavy adults also have higher rates of psychiatric disorders.

Using data from a national health survey of more than 40,000 Americans, researchers found that obese adults were up to twice as likely to suffer from depression, anxiety and other mental health conditions as normal-weight adults.

In addition, even moderately overweight people had elevated rates of anxiety disorders, the study found.

Whether excess pounds somehow lead to mental health problems is not clear, according to the researchers. But the findings do indicate that a range of psychiatric disorders are more common among overweight people.

They also suggest that briefly screening obese patients for such conditions could be useful, lead researcher Dr. Nancy M. Petry told Reuters Health.

She and her colleagues at the University of Connecticut Health Center in Farmington report their study findings in the journal Psychosomatic Medicine.

The findings are based on a government study of 41,654 U.S. adults who were assessed for recent and lifetime psychiatric disorders.

In general, Petry’s team found, obese adults had higher risks of major and milder depression, anxiety disorders like panic disorder and phobias, and “manic” episodes. They also showed higher rates of alcohol abuse and personality disorders, such as obsessive-compulsive behavior and paranoid personality disorder.

Among adults who were moderately overweight, rates of anxiety disorders were higher than those of normal-weight men and women.

The researchers could not fully investigate the reasons for all of these links, but use of psychiatric drugs — which can cause weight gain — did not explain the findings. They say behavioral, biological or genetic factors could all plausibly play a role in the relationship between weight and mental health.

For example, Petry explained, the links between weight and certain psychiatric disorders could point to a general “behavioral dysregulation,” where people deal with stress by overeating, as well as doing other things in excess.

Eating can also become in a “conditioned reinforcer” in some people, she said. This means that if a person habitually turns to food in response to anxiety, then eventually even minor stress may spur overeating.

SOURCE: Psychosomatic Medicine, April 2008.