Mood and anxiety disorders have positive associations with obesity in the
U.S. population, according to the results of a survey of 9,125 people. Unlike
earlier surveys, the study found no difference between men and women in the
association of obesity with psychiatric disorders, said Gregory Simon, M.D.,
M.P.H., and colleagues, writing in the July Archives of General
Social and cultural factors may play a significant role in connecting
obesity with depression, said Simon, of Group Health Cooperative in Seattle,
in an interview. "However, we can't say from the data what the direction
of causation is."
The researchers used data from the National Comorbidity Survey Replication
(NCS-R) to examine connections between obesity and mood, anxiety, and
substance use disorders in adults and whether these were also associated with
sociodemographic factors. Interviewers used DSM-IV criteria and
assessed participants using the World Mental Health version of the World
Health Organization Composite International Diagnostic Interview. The NCS-R
survey was conducted over one year beginning in February 2002 and was the U.S.
element of a worldwide study coordinated by the World Health organization.
The study concluded that obesity—defined as a body mass index (BMI)
of 30 or more—was associated with about a 25 percent increase in the
lifetime odds of mood and anxiety disorders and a 25 decrease in the odds of
substance use disorders. These may sound like modest effects, wrote Simon and
colleagues, but are important for public health reasons because of the high
levels of obesity in the U.S.
The study measured only association between the two conditions and could
not determine whether obesity caused mood and anxiety disorders or whether
mood and anxiety disorders induced obesity.
"Many mechanisms could explain the relationship, and possibly more
than one is involved," said Simon. "Some people eat more when
they're depressed and some eat less, for example."
The stigma attached to being overweight might also lead to depression, as
well, he said. "In social groupings where obesity is more stigmatized,
it might be equally true that people who can't lose weight become depressed,
or that depressed people can't lose weight."
In analyses of various sociodemographic subgroups, the association of
obesity with psychiatric disorders was strongest among respondents who were
younger than 30 years old, had a college education, or were of non-Hispanic
white ethnicity. Simon suggested that social and cultural factors may
therefore be important in understanding the connection. Similar studies in
China and Poland, for instance, found that increased obesity was associated
with less depression.
"I would imagine—although this study doesn't provide specific
evidence for it— that if obesity and depression vary with educational
and cultural settings, then a social environment that stigmatized obesity
would produce more depression and anxiety among overweight members of that
group," said Simon.
"We've seen that behavioral weight-loss interventions reduce weight
and also lower depressive symptomatology," said Eric Stice, Ph.D., a
senior scientist at the Oregon Research Institute in Eugene. "But
there's not much evidence that treating psychiatric problems leads to weight
"But there's probably a reciprocal relationship. The stress and
rejection caused by obesity lead to mood and anxiety problems, while those
problems lead to an increased risk of overeating."
Stigma is no small concern for the overweight, said Stice, who studies risk
factors that predict onset of eating disorders, obesity, and depression."
I'm amazed at what coaches, parents, and other children say about
overweight kids," he said.
The results of the NCS-R study highlight the importance of sociocultural
factors linking obesity and psychiatric disorders, said Simon. To explore that
link, he and his colleagues are now doing a series of smaller surveys to get
more information on the interaction of depression, obesity, diet, and physical
An abstract of "Association Between Obesity and Psychiatric
Disorders in the US Adult Population" is posted at<http://archpsyc.ama-assn.org/cgi/content/abstract/63/7/824>.▪