Abstract
Individuals with bipolar disorders (BD) frequently suffer from obesity, which is often associated with neurostructural alterations. Yet, the effects of obesity on brain structure in BD are under-researched. We obtained MRI-derived brain subcortical volumes and body mass index (BMI) from 1134 BD and 1601 control individuals from 17 independent research sites within the ENIGMA-BD Working Group. We jointly modeled the effects of BD and BMI on subcortical volumes using mixed-effects modeling and tested for mediation of group differences by obesity using nonparametric bootstrapping. All models controlled for age, sex, hemisphere, total intracranial volume, and data collection site. Relative to controls, individuals with BD had significantly higher BMI, larger lateral ventricular volume, and smaller volumes of amygdala, hippocampus, pallidum, caudate, and thalamus. BMI was positively associated with ventricular and amygdala and negatively with pallidal volumes. When analyzed jointly, both BD and BMI remained associated with volumes of lateral ventricles and amygdala. Adjusting for BMI decreased the BD vs control differences in ventricular volume. Specifically, 18.41% of the association between BD and ventricular volume was mediated by BMI (Z = 2.73, p = 0.006). BMI was associated with similar regional brain volumes as BD, including lateral ventricles, amygdala, and pallidum. Higher BMI may in part account for larger ventricles, one of the most replicated findings in BD. Comorbidity with obesity could explain why neurostructural alterations are more pronounced in some individuals with BD. Future prospective brain imaging studies should investigate whether obesity could be a modifiable risk factor for neuroprogression.
Highlights
Bipolar disorders (BD) are among the most disabling and expensive psychiatric illnesses [1,2,3]
We focused on subcortical volumes, as these regions, including amygdala [20, 24, 38], hippocampus [19, 20, 38,39,40], striatum [19, 20, 39, 41], thalamus [19, 20, 24, 39, 40] or lateral ventricles [42] were previously associated with obesity
As the rates of monotherapy were low in this sample, we studied the association between number of medication classes used and body mass index (BMI) or subcortical volumes
Summary
Bipolar disorders (BD) are among the most disabling and expensive psychiatric illnesses [1,2,3]. Some individuals with BD show marked neuroimaging alterations, whereas the brains of others appear to be comparable to those of controls [4, 5]. The strength and even the direction of associations between BD and individual brain imaging measures vary widely across studies [6,7,8,9,10]. One potential source of differences among individuals with BD is the comorbidity with medical conditions known to affect the brain [11]. One such condition, which targets the brain and is disproportionately frequent in BD, is obesity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
