Response to pharmacotherapy and hypofrontality assessed by near-infrared spectroscopy in major depression: Comparison between responders and non-responders

Approximately 30% of patients with depression are reported to be treatment-resistant, and a number of bio-psycho-social factors are known to influence responsiveness to pharmacotherapy. In the present study, we investigated whether pre-treatment frontal functions of patients with depression as measured by near-infrared spectroscopy (NIRS) would predict future responsiveness to pharmacotherapy. Thirty-two drug-naive outpatients with major depressive disorder participated in the present study. All the patients were started with antidepressants and their clinical symptoms were evaluated twice with the Hamilton Rating Scale for Depression (HRS-D), on their first visit and 8-12 weeks after the beginning of pharmacotherapy. All patients received multi-channel NIRS on their first visit, and their frontal reactivity was measured by changes in oxy-hemoglobin concentration in the frontal lobes. Comparison of pre-treatment NIRS findings demonstrated that the overall increase of oxy-hemoglobin in responders was lower than that in non-responders, with significant differences in channels in the medial frontal areas. The results suggest that the treatment-responsive patients with depression demonstrated typical hypofrontality as has been reported in previous literature. In contrast, NIRS findings of the treatment-resistant depressive patients were similar to those reported in healthy persons, suggesting that patients with atypically preserved frontal reactivity may respond minimally to antidepressants. Pre-treatment hypofrontality of patients with depression as measured by NIRS may be useful for predicting future responsiveness to pharmacotherapy.