Association between longitudinal changes in prefrontal hemodynamic responses and social adaptation in patients with bipolar disorder and major depressive disorder

Abstract Background Patients with affective disorders exhibit changes in regional brain function and show abnormal social adaptation. However, to our knowledge, no near-infrared spectroscopy (NIRS) study has examined the relationship between these two phenomena longitudinally. This study examined the region-specific functional abnormality associated with bipolar disorder (BD) and major depressive disorder (MDD), and the association between particular longitudinal changes in regional activation and social adaptation. Methods We evaluated frontotemporal functioning during a verbal fluency test (VFT) for patients with BD ( N =18), those with MDD ( N =10), and healthy controls (HCs; N =14) using NIRS. NIRS measurements and the Social Adaptation Self-evaluation Scale (SASS) were administered twice with an interval of approximately 6 months. Results The BD and MDD groups showed lesser activation than the HCs in the bilateral ventro-lateral prefrontal cortex and the anterior part of the temporal cortex (VLPFC/aTC). Longitudinal changes in SASS scores were positively associated with the extent of change in left VLPFC/aTC activation in the BD group and with right VLPFC/aTC activation in the MDD group. Limitations Our small sample size limited statistical power, and the effect of medication and multiple comparisons cannot be excluded, although these effects were considered in the interpretation of the present results. Conclusion Longitudinal increases of VLPFC/aTC activation were associated with improvement in social adaptation in patients with BD and those with MDD. NIRS measurement could be a useful tool for objective evaluation of changes in social adaptation in BD and MDD.