Long-term Monitoring of NIRS signals for Mental Health Assessment

Mental disorder caused by chronic stress is mostly difficult to be aware of by oneself. There are social barriers including lack of perceived need for mental health services even if the potential patients have the desire to receive healthcare support. On the other hand, self-report inventories such as the Beck Depression Inventory (BDI-II) and State-Trait Anxiety Inventory (STAI) can tell the emotional valence as a screening test for depressive and anxiety disorders, which are the key elements in the mental health assessment. However, the results of the self-report inventories themselves are not sufficient tool to persuade the test respondents to clearly understand how the results can be serious and the causal factors can affect the mental state in their recent life-style. On the other hand, Laterality Index at Rest (LIR) has been proposed for evaluation of mental stress level from the analysis of dynamic changes in oxygen concentration in the prefrontal cortex at the resting-state. This study practically applies LIR for the long-term lifelog monitoring. Correlation analysis on LIR, STAI and BDI-II for 19 young subjects was first performed, and then compared with the temporal changes in the lifelog including the sleep time and the amount of physical activity. Importantly, LIR correlates to both STAI and BDI scores in the time series with different cycles.