Effect of Radiance-Dimmer Devices Simulating Natural Sunlight Rhythm on the Plasma Melatonin Levels and Anxiety and Depression Scores of the Submarine Personnel

Objective: Not perceiving circadian shifts of sunlight due to living in enclosed environments may have deleterious effects on mental health and plasma parameters. This study aimed to determine the effect of dim regulation on the submarine personnel of Iranian Navy forces by radiating devices according to natural circadian sunlight shifts. Also, this study aimed to investigate the impact of mimicking sunlight circadian by artificial radiance luminating devices on the serological and psychological measures of submarine personnel. Method: Participants were randomly assigned to experimental and control groups in this non-randomized controlled trial. There were 26 participants in each group, and they were all male aged 21-29 years. Both groups were living in the submarine underground hall, with 120 meters 2 area with constant radiance with the same intensity. The experimental group had been given extra lighting devices with changing radiance intensity according to the natural sunlight circadian cycles. Plasma melatonin levels and depression and anxiety scores were determined before and after the experiment for both groups. Minnesota Multiphasic Personality Inventory (MMPI) and Cattell’s Anxiety Scale Questionnaire (IPAT) were used to measure depression and anxiety, respectively. Results: Findings indicate that the plasma melatonin levels (-16.2±13.6 vs 8.0±9.3 mg/dL, respectively; p<0.001), depression scores (-6±6 vs 3.9±5.4, respectively; p<0.001), and anxiety scores (-1±1.2 vs 0.73±1.04, respectively; p<0.001) significantly reduced in the experimental group compared to the control group. Conclusion: Using radiance dimmers, with a radiance intensity regularity according to the sunlight, is effective in improving psychiatric and plasma parameters and can be used in closed occupational environments such as underground environments and submarine halls.