Prefrontal cortex hypoactivity distinguishes severe from mild-to-moderate social anxiety as revealed by a palm-sized near-infrared spectroscopy system.

The purpose of this study was to compare prefrontal cortex (PFC) activity among subjects with differing social anxiety (SA) severity levels to identify a possible biomarker for severe SA. Further, SA is generally under-diagnosed, so we examined if such measurements could be acquired conveniently, non-invasively, and at low cost using a portable near-infrared spectroscopy (NIRS) system. We classified 96 participants into three groups based on Liebowitz Social Anxiety Scale (LSAS) total score: Low SA (LSA, n = 40), Moderate SA (MSA, n = 39), and High SA (HSA, n = 17). We compared the prefrontal hemodynamic responses among LSAS severity groups during a verbal fluency task using a palm-sized NIRS system. The HSA group exhibited a significantly lower hemodynamic response in the left PFC compared to LSA and MSA groups, whereas there was no significant difference between LSA and MSA groups. There was also no significant difference in the right PFC hemodynamic response among groups. Differences in the severity of SA symptoms may be related to the left PFC function. Low PFC activity during specific cognitive tasks may provide a biomarker for distinguishing severe from mild/moderate SA symptoms to guide subsequent therapeutic decisions.