Discussion
impulsivity
PHYSIOLOGICAL STRESS, CORTEX
This study assessed the effects of listening to nature- and city-based sounds among individuals with GD. The participants' responses to auditory stimuli were investigated under laboratory conditions. In this research, we reduced the elements of the natural environment to a single stimulus to simplify the evaluation. We focused on the sound of buzzing insects, which is one of the natural environmental elements. Then, the reaction of participants with GD to this sound alone was evaluated. The following results were obtained: (1) listening to nature sounds significantly reduced the oxy-Hb concentrations in the bilateral prefrontal cortex. (2) The results of the assessment using the modified SD method showed that nature-based stimuli significantly increased comfort, relaxation, and natural feelings. (3) The POMS2 negative subscale scores significantly decreased after listening to nature sounds compared with city sounds.Song et al. showed that various nature therapies had physiological relaxation effects on activities in the central nervous system, ANS, endocrine system, and immune system, from the perspective of EBM.Furthermore, our results are also consistent with those of previous reports on the physiological and psychological relaxation effects of nature-based auditory stimuli on patients with GD.From the perspective of neurotransmitters, an inseparable relationship between stress and the risk of developing addiction can be observed,However, several limitations must be considered when interpreting the results of this study. First, a risk of selection bias is present because the participants had stable symptoms based on the assessment performed by psychiatrists. Second, we limited our experiments to men as GD tends to be predominant in men. Thus, further studies should be conducted to examine the relationship between impulsivity and physiological stress responses among individuals with GD, especially women.Third, the exposure time to the stimuli was short. Since we compared the relaxation levels before and 1 min after exposure to stimulation using nature and city sounds, the results were only preliminary. Fourth, we did not check the extent of participants' contact with nature. The frequency of contact with nature could influence the results. The relationship between specific stimuli and biological responses is a complex research topic that is challenging to investigate. Therefore, more extensive research about the appropriate extent, duration, and frequency of stimulus exposure and types of stimuli should be conducted.