Figure 2. Distribution of Serotonin Level Based on Participants’ Characteristics. a) Serotonin level based on gender, b) serotonin level based on age categories, c) serotonin level based on transmission history, d) serotonin level based on occupation, and e) serotonin level based on education. The p-values were obtained using the Mann–Whitney U test with a 95% level of confidence (α=0.05). All p-values did not show a significant difference.