New research published on bmj.com today reports that people with ordinary mental disorders such as depression and anxiety are at increased risk of becoming obese.

The authors say their findings also indicate that individuals with chronic or repeat episodes of common mental disorders are particularly at risk.

Earlier studies report conflicting results. It remains unclear if common mental disorders lead to an increased risk of obesity, or if obesity is a risk factor for future mental disorders. It is vital to understand the link between these common conditions because they have a major impact on health care systems. This knowledge could assist in reaching effective treatment and prevention.

In order to find out more, researchers led by Mika Kivimäki from University College London, investigated the pattern and probable dose-response nature of the connection between common mental disorder and obesity.

They based their research on four medical screenings of 4,363 British civil servants aged between 35 and 55 years old, between 1985 and 2004. Each screening included a standardized evaluation of common mental disorder (General Health Questionnaire) and measurement of height and weight from which body mass index (BMI) was calculated.

Several factors were taken into account, including use of medicines for mental disorders. It appeared that weight gain was more frequent among individuals with common mental disorder symptoms at the start of the study, than among those who were symptom free.

Individuals with a common mental disorder at all three earlier screenings were twice as likely to be obese at the final screening compared to symptom free individuals at all previous screenings.

Also, there was obvious evidence of a dose-response relationship. It indicated that those who experienced more incidences of a common mental disorder had a greater risk of weight gain and obesity.

An interesting fact is contradictory to prior research: there was little evidence that obesity leads to common mental disorders in people with no pre-existing mental disorder.

“In this population of British middle-aged adults common mental disorder is predictive of subsequent weight gain and obesity”, explain the authors. They inform that further research is needed to verify how the findings can be generalized to wider populations.

They say in closing that if their observed associations are causal, their findings will have significant implications for prevention and treatment.

In an accompanying editorial, researchers from the University of Adelaide remark that although Kivimäki and colleagues found little evidence that obesity predicts depression or anxiety, clinicians should be aware that this association can occur in both directions.

They recommend further research on the most beneficial approach in order to deliver lifestyle interventions. This includes government action on taxes, tariffs, and trade laws to encourage the supply and consumption of healthy food and physical activity choices.

“Common mental disorder and obesity―insight from four repeat measures over 19 years: prospective Whitehall II cohort study”
Mika Kivima¨ki, professor of social epidemiology, Debbie A Lawlor, professor of epidemiology, Archana Singh-Manoux, senior research fellow, G David Batty, Wellcome Trust fellow, Jane E Ferrie, senior research fellow, Martin J Shipley, senior lecturer in medical statistics, Hermann Nabi, research fellow, Séverine Sabia, research fellow, Michael G Marmot, head of department and director, Markus Jokela, senior research fellow
BMJ 2009; 339:b3765
doi:10.1136/bmj.b3765

“Obesity and depression or anxiety”
Evan Atlantis, early career research fellow, Robert D Goldney, professor emeritus, Gary A Wittert, professor
BMJ 2009; 339:b3868
bmj.com

Written by Stephanie Brunner (B.A.)