Objective: We recently reported that in patients with BD, clinically significant weight gain (CSWG) occurs very rapidly following the first manic episode, and is associated with pronounced functional impairment. In non-psychiatric samples, elevated body mass index (BMI) is correlated with reduced global brain volume. However, despite the prevalence of obesity in BD and its association with poor outcomes, no studies have examined the relationship between BMI and brain structure in patients with BD.
Methods: Here, we report data on body mass index (BMI) and normalized brain volume (NBV), measured using MRI, in 46 patients with BD enrolled in the Systematic Treatment Optimization Program for Early Mania (STOP-EM), and 22 age- and gender-matched healthy subjects who were recruited for comparison purposes. BMI was calculated using the formula BMI = weight (kg) / height (m)2. Brain volumes were normalized using the formula NBV = (total grey matter + total white matter) / (total grey matter + total white matter + total CSF volume) to control for inter-individual differences in intracranial volumes. We calculated Pearson correlation coefficients to examine the association between BMI and NBV for patients and healthy subjects one year after the initial manic episode.
Results: No difference was observed between patients and healthy subjects in NBV (.878 vs .873; p=NS). Our preliminary data analysis showed that in healthy subjects, 1-year BMI was negatively correlated with 1-year normalized brain volume (r=-.494, p=.02). In contrast, a significant correlation was not observed between BMI and brain volumes in patients with BD (r=.030, p=.86).
Conclusions: The neurobiological sequelae of weight gain may be different in patients with BD and healthy subjects. We will conduct additional analyses of specific regional brain volumes to further clarify the association between BMI and brain structure in BD.