Bipolar disorder is one of the most disabling medical conditions among adolescents worldwide. Similarly, being overweight or obese is common in adolescents and is known to confer risk for cardiovascular disease and other poor health outcomes in adulthood. As a result, the intersection of bipolar disorder and overweight is a matter of clinical and public health concern. Previous studies have demonstrated that overweight and obesity are more prevalent among adults with bipolar disorder as compared to the general population, and that overweight and obesity are associated with proxies of increased bipolar disorder severity, such as suicide attempts and greater symptom burden. Thus far, little is known about overweight among adolescents with bipolar disorder.

A study published in the December 2016 issue of the Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP) is the first to examine this topic in a large, representative sample of the US adolescent population. The NCS-A is a face-to-face survey of mental disorders in a representative sample of adolescents 13-17 years old. Participants included 295 adolescents with bipolar disorder, 1,112 with major depressive disorder, and 8,716 with neither of these conditions. 37.9% of adolescents with bipolar disorder were also overweight, compared to 32.4% of adolescents with major depressive disorder, and 32% of adolescents with neither of these conditions -- differences that were not statistically significant.

"We were somewhat surprised about the fact that obesity was not more prevalent among the adolescents with bipolar disorder compared to their peers. But this is good news, as it confirms that there is a window of opportunity to intervene in order to prevent the increased risk of obesity that is evident in adults and in clinical samples of adolescents with bipolar disorder," said Dr. Benjamin Goldstein, director of the Centre for Youth Bipolar Disorder in Toronto's Sunnybrook Health Sciences Centre, and lead author of the study.

The researchers also found that although overweight is not more common among adolescents with bipolar disorder than other adolescents, overweight adolescents with bipolar disorder showed signs of increased illness severity, including more suicide attempts, psychiatric hospitalizations for depression, co-occurring conduct disorder and bulimia/binge-eating, and history of physical or sexual abuse.

"It is concerning that despite the fact that this a non-clinical sample, the links between obesity and indicators of greater bipolar disorder severity are already evident. Some have wondered whether these links are secondary to greater exposure to psychiatric medications, some of which confer risk of weight gain, among adolescents with greater severity of bipolar disorder," added Dr. Goldstein. "Our findings, based on a community sample with low rates of medication use, confirm that there is more to the story than medications -- there appears to be a direct relationship between obesity and greater severity of bipolar disorder."

Asked what next steps should be taken, Goldstein responded: "The main clinical question now becomes: what strategies are most effective for preventing obesity in this specific group of teens, for whom the risks of obesity in terms of both physical and mental health may be especially significant? The answer to that question will require additional research, informed in part by the findings of this study. In addition, there are scientific questions about the biological, psychological, and environmental factors that explain the increased severity of bipolar disorder among obese teens with bipolar disorder."

To that end, Goldstein and his team are studying how overweight is associated with brain structure, cognition, and blood markers of inflammation and other processes, among adolescents with bipolar disorder. Goldstein is planning to study intervention strategies to prevent and treat overweight among adolescents with bipolar disorder, and is hopeful that if successful these strategies will improve mental as well as physical health. "Wouldn't it be interesting, and efficient, if an intervention focused on optimizing weight could also yield mental health benefits?" he concluded.