Depression in children is often linked with obesity. But it seems to be a case of chicken and egg. The two conditions often occur together, but it is unclear exactly which is cause and which is effect.
Obesity rates are soaring. One study, published in Pediatrics, found that the longer a child is overweight, the more he or she is at risk for depression and other mental health disorders.
The study followed nearly 1,000 white children in North Carolina, ages 9 to 16, over eight years. Young boys, but not girls, proved especially prone to the dual problem of obesity with depression.
"The link could have to do with social factors or it could be neuroendocrine-related," says Sarah Mustillo, Ph.D., of Duke University Medical Center. "It could be that if you're only obese for six months, there's not as much of an effect as if you were obese for five years."
At the center of obesity-depression link is biology, notably the hormonal pathway known as the HPA axis. It is the route of communication between the hypothalamus, the peanut-sized part of the brain that governs parts of the nervous system, and the pituitary and adrenal glands, which secrete a variety of hormones.
These three points of the body work together to maintain chemical equilibrium when the body is under stress. The HPA axis is responsible for releasing cortisol, the so-called "stress hormone." It plays a critical role in energy metabolism as well as other functions. The problem is, cortisol prompts the body to deposit fat around the abdomen, a pattern that is especially hazardous to health. Chronic stress also begets depression.
"Obesity, depression and behavioral disorders have all been linked to abnormal functioning of the HPA axis," says Mustillo. While social factors such as teasing and isolation may contribute to depression in obese kids, Mustillo believes the problem is much more complex.
"It's probably a combination of social and biological factors," she says, noting, "There's an interaction between what's outside your body and what's inside." Obesity carries a large social stigma and may bring on depression if it negatively affects self-esteem, body image or social mobility. It may even disrupt the normal hormonal pathways. Then again, depression may also bring on obesity, if a child lacks the energy to exercise or is immobilized by stress.
About 15% of the children Mustillo studied were chronically obese. Another 12% were obese at some point in childhood or adolescence. She believes the obesity epidemic among children is actually three to four times worse than the Centers for Disease Control says.
Depression, of course, is not the only problem for these kids. Another study, published in the Journal of the American Medical Association, found that obese kids were 5.5 times more likely to have an impaired quality of life than healthy kids, putting their life experience on par with that of kids undergoing chemotherapy treatment for cancer.
"Obese children reported scores [on a quality of life survey] that were as bad as cancer patients in each and every domain of life," says Jeffrey Schwimmer, M.D., of the University of California San Diego. "We were surprised it was that bad."
Obese children also missed four days of school a month, compared to less than a day for kids of average weight. "The potential ramifications are huge," says Schwimmer, who believes the low quality of life among overweight kids hinges on their medical problems—they are physically unable to take part in many activities—as well as on how other children treat them.
The best thing parents can do is to treat obesity as a health issue, not a problem of appearance, and to accurately record their child's height and weight. He urges parents, physicians and psychologists to press insurance companies to cover behavioral therapy for obesity.
It's also important to recognize that obesity isn't necessarily caused by overeating. Says Elizabeth Goodman, M.D., of Brandeis University: "There are different types of depression and different types of obesity. It's easy to say that it's all behavioral. That makes it sound like there's a choice; I'm not sure that it is."