Which comes first: Obesity or depression?

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Obesity and depression are often linked, but it’s not clear whether one condition tends to precede the other. One new study suggests depression may help cause obesity, but obesity doesn’t necessarily cause depression.

Researchers at the University of Alabama, Birmingham, looked at data from a longitudinal study of more than 5,000 men and women ages 18 to 30. Over the 20-year study, participants’ waist circumference and body mass index was measured and they were asked about symptoms of depression.

The study found that the waist circumference among the people who started the study with depression was about 1 inch larger than those who started the study reporting lower levels of depression. This was true regardless of race, gender, ethnicity and education level. In contrast, those who started the study with higher body-mass index and waist circumference did not show a change in depression symptoms over time.

‘If you are interested in controlling obesity, and ultimately eliminating the risk of obesity-related diseases, then it makes sense to treat people’s depression,’ the lead author of the study, Belinda Needham, said in a news release.

There is a possible physiological explanation why the two conditions occur together. Both conditions are linked to higher levels of the stress hormone cortisol.

The study is published in the June issue of the American Journal of Public Health.

-- Shari Roan