Individuals at increased risk for development of bipolar disorder display structural alterations similar to people with manifest disease

Abstract

In psychiatry, there has been a growing focus on identifying at-risk populations. For schizophrenia, these efforts have led to the development of early recognition and intervention measures. Despite a similar disease burden, the populations at risk of bipolar disorder have not been sufficiently characterized. Within the BipoLife consortium, we used magnetic resonance imaging (MRI) data from a multicenter study to assess structural gray matter alterations in N = 263 help-seeking individuals from seven study sites. We defined the risk using the EPIbipolar assessment tool as no-risk, low-risk, and high-risk and used a region-of-interest approach (ROI) based on the results of two large-scale multicenter studies of bipolar disorder by the ENIGMA working group. We detected significant differences in the thickness of the left pars opercularis (Cohen's d = 0.47, p = 0.024) between groups. The cortex was significantly thinner in high-risk individuals compared to those in the no-risk group (p = 0.011). We detected no differences in the hippocampal volume. Exploratory analyses revealed no significant differences in other cortical or subcortical regions. The thinner cortex in help-seeking individuals at risk of bipolar disorder is in line with previous findings in patients with the established disorder and corresponds to the region of the highest effect size in the ENIGMA study of cortical alterations. Structural alterations in prefrontal cortex might be a trait marker of bipolar risk. This is the largest structural MRI study of help-seeking individuals at increased risk of bipolar disorder.

Fig. 1. ROI-based analysis of cortical thickness by individuals at increased risk for development of bipolar disorder.

A Left inferior frontal gyrus—pars opercularis as defined by the Desikan−Killiany atlas. B Mean thickness of the left pars opercularis. The post hoc tests revealed a significantly thinner cortex of the left pars opercularis between no-risk and high-risk groups. The low-risk group tends to have lower thickness than the no-risk group, while having a greater thickness than the high-risk group. However, these differences were not significant. ^* denotes statistical significance at p = 0.012 (FDR-corrected). Error bars represent the 95% confidence intervals.