For the study, researchers evaluated over 1,500 participants (ages 11-24) in Minnesota over a 10-year period and found that females with depression in early adolescence were more likely to become obese by late adolescence.
Furthermore, females with obesity in late adolescence were more likely to experience depression by early adulthood. No significant links between the two disorders were found in males during the study.
“When researchers looked at this connection over time, data had been mixed,” said Dr. Naomi Marmorstein, an associate professor of psychology at Rutgers-Camden.
“Some found that depression and obesity go hand-in-hand, while others did not see that connection. We tried to take the next step in clarifying this link by looking at a sample of youth that we followed from ages 11 to 24.”
The study, published in the International Journal of Obesity, is co-authored with psychology professor Dr. William Iacono of the University of Minnesota and research associate Lisa Legrand, Ph.D.
The new study improves on past research by focusing on the onset of each disorder, rather than just recurrence or persistence of the two conditions.
Participants in the new study were assessed at ages 11, 14, 17, 20, and 24 by using height and weight measurements and clinical, interview-based diagnosis of major depressive disorder. The participants were checked for onsets of either disorder by age 14, between the ages of 14 and 20, and between ages 20 and 24.
Marmorstein said her study was not designed to investigate the reasons for these links, but that other theories and research offer possible explanations. She said depression can lead to obesity through an increased appetite, poor sleep patterns, and lethargy, while obesity can cause depression due to weight stigma, poor self-esteem, and reduced mobility.
“When a person is young, she is still developing eating and activity patterns, as well as coping mechanisms,” Marmorstein explained. “So if she experiences a depressive episode at age 14, she may be more at risk for having an onset of unhealthy patterns that persist.”
Furthermore, a child who is obese may be more susceptible to negative societal messages about obesity or teasing, which could contribute to depression.
“At this age, adolescents are starting to establish relationships becoming self-conscious, so teasing can be particularly painful,” Marmorstein said.
“Prevention efforts aimed at both of these disorders at the same time when just one is diagnosed might help in decreasing their prevalence and comorbidity,” she added.
“When an adolescent girl receives treatment for depression, the clinician might consider incorporating something relating to healthy eating and activity,” she said. “Exercise can assist in the treatment of depression to begin with, so it seems like a good reason to combine prevention efforts for both depression and obesity.”
It is still unknown why they found no links between obesity and depression in males, but Marmorstein hypothesizes that it could be a result of different developmental processes leading to obesity and depression in males and females.
Source: Rutgers University