Obesity in patients with major depression is related to bipolarity and mixed features: evidence from the BRIDGE-II-Mix study

Objectives: The Bipolar Disorders: Improving Diagnosis, Guidance and Education (BRIDGE)-II-Mix study aimed to estimate the frequency of mixed states in patients with a major depressive episode (MDE) according to different definitions. The present post-hoc analysis evaluated the association between obesity and the presence of mixed features and bipolarity. Methods: A total of 2811 MDE subjects were enrolled in a multicenter cross-sectional study. In 2744 patients, the body mass index (BMI) was evaluated. Psychiatric symptoms, and sociodemographic and clinical variables were collected, comparing the characteristics of MDE patients with (MDE-OB) and without (MDE-NOB) obesity. Results: Obesity (BMI ≥30) was registered in 493 patients (18%). In the MDE-OB group, 90 patients (20%) fulfilled the DSM-IV-TR criteria for bipolar disease (BD), 225 patients (50%) fulfilled the bipolarity specifier criteria, 59 patients (13%) fulfilled DSM-5 criteria for MDEs with mixed features, and 226 patients (50%) fulfilled Research-Based Diagnostic Criteria for an MDE. Older age, history of (hypo)manic switches during antidepressant treatment, the occurrence of three or more MDEs, atypical depressive features, antipsychotic treatment, female gender, depressive mixed state according to DSM-5 criteria, comorbid eating disorders, and anxiety disorders were significantly associated with the MDE-OB group. Among (hypo)manic symptoms during the current MDE, psychomotor agitation, distractibility, increased energy, and risky behaviors were the variables most frequently associated with MDE-OB group. Conclusions: In our sample, the presence of obesity in patients with an MDE seemed to be associated with higher rates of bipolar spectrum disorders. These findings suggest that obesity in patients with an MDE could be considered as a possible marker of bipolarity.