Effects of Mid-Infrared Light Intervention on Mood, Executive Control and Autonomic Nervous System Activity in Young Adults with Sub-Clinical Psychological Distress: An Exploratory Randomized Controlled Trial

ABSTRACT: The purpose of this study was to investigate the effects of Mid-infrared light on executive control functions and autonomic nervous system dysregulation in early adulthood in screen-positive for depression and general psychological symptoms group. The Symptom Checklist-90 (SCL-90) and the Depression Screening Questionnaire (PHQ-9) were administered online to 74 adolescent participants aged 18–22 years. Functional near-infrared brain imaging (fNIRS) was used to test brain function during the Stroop task, and heart rate variability (HRV) devices were used to test the autonomic nervous system. After a two-week Mid-infrared light intervention, subjects showed significant improvement in their depressive symptoms and psychological distress. The mean strength of brain functional connectivity was much more increased in the screening positive group, and significantly decreased after intervention. HRV measure showed significant differences across several indicators: LF, HF, LF/HF, SDNN, and RMSSD between screening positive and health control, and significant improvements in several key indicators: LF/HF, RMSSD, and HF after intervention. This integration of mood, HRV, and functional brain imaging data provides a comprehensive view of Mid-infrared light interventions, which can restore autonomic balance and enhance cognitive efficiency, highlighting its potential as a non-pharmacological approach worthy of further investigation for regulating mood and cognitive function. It is important to underscore that this study is exploratory and hypothesis-generating in nature. The modest sample size from a single population limits generalizability. The lack of pre-registration and the control condition, which did not fully mimic the device’s placebo effect, are notable limitations. Consequently, all findings should be interpreted as preliminary, serving primarily to generate hypotheses and guide the design of more definitive future studies, rather than to inform direct clinical practice. Future research necessitates larger-scale, pre-registered, double-blind, sham-controlled trials to verify these initial observations.