Relaxation Effect of Nature Sound Exposure on Gambling Disorder Patients: A Crossover Study

Gambling disorder (GD) has been associated with economic, social, mental, and physical problems. Alternative leisure activities or stress-relieving activities have been adopted as part of GD treatment. Moreover, it has been proven that activities utilizing the natural environment, such as shinrin-yoku, have a relaxing effect on healthy people. In this study, we examined the physiological and psychological responses of patients with GD to determine whether nature therapy could reduce their stress responses. This study included 22 Japanese male participants who were found to be pathological gamblers, with a South Oaks Gambling Screen score of ≤5. We exposed the participants to the digital nature sounds of insects and city sounds of a scramble intersection. The nature and city sounds were presented in a counterbalanced order. A two-channel near-infrared spectroscopy system was used to measure the changes in oxyhemoglobin (oxy-Hb) concentrations in the bilateral prefrontal cortex. The heart rate variability was measured to evaluate the autonomic nervous activity. Subjective evaluation was performed using the modified version of the semantic differential method and the Profiles of Mood States, Second Edition (POMS2). The oxy-Hb level in the bilateral prefrontal cortex significantly decreased. No significant difference in the high-frequency (HF) and low-frequency/HF ratio was observed. The subjective evaluation indicated that the participants experienced increased comfort and relaxation and had more natural feelings. Nature sounds significantly decreased the POMS2 negative emotion subscale and total mood disturbance scores and increased the positive emotion subscale scores. Nature-based stimulus exposure induces physiological relaxation and other positive effects among individuals even with GD. Exposure to nature-based sounds induces physiological relaxation and other positive responses among individuals with GD. In patients with GD, nature sounds produce the same relaxation response as in healthy individuals. (Umin.ac.jp under registration number: UMIN000042368).