Common Mental Health Disorders Strongly Linked to Obesity Risk

Janis Kelly

August 14, 2009

August 14, 2009 — Common mental health disorders such as depression and anxiety are strongly linked to an increased risk for obesity — an association that grows stronger as individuals age, new research suggests.

In a large, population-based, longitudinal study, investigators from University College London in the United Kingdom found that at that age 40 years, 6% of subjects were obese, and that at this age, there no differences in the proportion of mentally healthy subjects who were obese in comparison with those who had mental health disorders.

However, at age 70 years, 35% of participants who had common mental health disorders were obese compared with 27% of those without mental disorders (odds ratio, 1.46). The risk of being obese did not vary by sex, ethnic background, or socioeconomic status.

"This study emphasizes the role of common mental disorders in the risk of obesity at older ages. There is a need for more detailed clinical guidelines to help doctors prevent and treat obesity among adults with mental health disorders, and promote better mental health among older people who are obese," the authors write.

The study is published in the August issue of the British Journal of Psychiatry.

The study included 10,166 civil servants aged 35 to 55 years. Each was classified as obese (body mass index ≥ 30 kg/m2) or nonobese. Participants also completed a General Health Questionnaire, which focuses on self-reported symptoms of anxiety and depression and associated psychosocial dysfunction. These tests were repeated another 3 times during a 19-year follow-up period.

The authors report that the excess risk for obesity in the presence of mental disorders increased with age (P = .004). The estimated proportion of individuals who were obese was 5.7% at age 40 years, both in the presence and absence of mental disorders, but the corresponding figures were 34.6% and 27.1%, respectively, at age 70 years.

Generalizeable to Younger Populations?

Asked by Medscape Psychiatry to comment on the article, Susan L. McElroy, MD, from the University of Cincinnati College of Medicine, Ohio, said the study makes "an important contribution to the literature on the relationship between mental illness and obesity."

"This is probably the largest and longest study to show that age affects the relationship between obesity and common mental disorders," Dr. McElroy said. "However, as the mean age of the cohort was in the early [to] mid-40s at study initiation, these findings cannot be generalized to younger cohorts, where there may also be obesity–psychopathology relationships," she said.

The researchers suggested that this difference might mean that common mental health problems could be a cause of obesity, that weight gain might be in part a result of side effects from medications for depression, that obese individuals may have a poor self-body image and be at greater risk of developing mental health problems, or that concomitant health problems associated with aging might cause both weight gain and depression or anxiety, Dr. McElroy added.

Question of Age Still Unsettled

Gregory Simon, MD, psychiatrist and researcher at Group Health Cooperative in Seattle, Washington, told Medscape Psychiatry that this study confirms and is consistent with the results of many previous studies indicating that there is a strong association between obesity and psychological distress that manifests as symptoms of depression and anxiety.

However, Dr. Simon said that although the Kivimaki study found that this association was absent in younger people and increased with age, his data show that depression and obesity were similarly associated in younger and older people.

"This difference in findings may be due to differences in study methods. For example, the Kivimaki study used the General Health Questionnaire, while other studies have used different measures. It's possible that there are age differences in how people respond to these different measures of psychological distress or depression," said Dr. Simon.

"At this point, I would say the age question (does the relationship between obesity and depression vary by age?) is still unsettled. But this study adds to many others showing that, in general, obesity and depression are strongly related," he added.

Dr. Simon said the implications for clinicians include the need to consider that obesity is very common among people with depression and that treatment for depression will often need to consider the challenges of obesity and the possible effects of medications on weight.

"Depression is especially common among people who are overweight or obese, so clinicians should be prepared to identify depression and discuss treatment options," he said.

The study was funded by the Medical Research Council, British Heart Foundation, UK Health and Safety Executive, National Heart Lung and Blood Institute, National Institute on Aging, Agency for Health Care Policy Research, and the John D. and Catherine T. MacArthur Foundation. The authors have disclosed no relevant financial relationships.

Br J Psychiatry. 2009;195:149–155.

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