Demographic variables and scores of the various measures
Participant demographic variables and scores on the various measures are presented in Additional Table
1. Although, we planned to recruit 2700 participants, a total of 2708 participants were included, with a mean age of 49.16 years (standard deviation (SD) = 16.32). Nearly the same number of individuals were in each age group (20s - 60s, all
N = 454, 16.8%; 70s,
N = 438, 16.2%), the same number of males and females were included (both
N = 1354, 50%), and nearly the same number of individuals were included in each employment status category (full-rime worker,
N = 956, 35.3%; no regular employment,
N = 876, 32.4%; unemployed including homemaker, retired, and jobless,
N = 876, 32.4%) since the survey used a quota sampling method to compare equal numbers across age groups, sexes, and employment statuses.
Based on the cut-off score of the PHQ-9, the number of patients in the no-depression group was 2211 (81.65%), and the number of patients in the probable depression group was 497 (18.35%). The probable depression group was younger (t = 12.91, df = 800.41, p < 0.001, d = 0.62), with a greater percentage of individuals in their 20s and 30s and a lower percentage of individuals in their 60s and 70s (χ2 = 146.65, p < 0.001), and included a greater percentage of males (χ2 = 10.41, p = 0.001), a lower percentage of full-time workers and homemakers and a greater percentage of individuals not working (χ2 = 55.79, p < 0.001), a greater percentage of participants with underlying disease (χ2 = 4.95, p = 0.026), a greater percentage of individuals who were single (χ2 = 129.1, p < 0.001), a greater percentage of those with less than 2 million JPY household income and a lower percentage of those with more than 8 million JPY (χ2 = 44.84, p < 0.001), and a lower percentage of participants who experienced no economic impact and a greater percentage of participants who experienced a negative economic impact (χ2 = 29.68, p < 0.001) than the no-depression group.
Regarding scores on measures, the probable depression group had higher scores on the PHQ-9 (t = 57.83, df = 594.89, p < 0.001, d = 3.21), state anger (t = 17.21, df = 588.98, p < 0.001, d = 0.96), self-distraction (t = 5.25, df = 2706, p < 0.001, d = 0.26), denial (t = 3.74, df = 651.29, p < 0.001, d = 0.20), substance use (t = 7.21, df = 636.19, p < 0.001, d = 0.39), use of emotional support (t = 2.74, df = 681.25, p < 0.01, d = 0.15), use of instrumental support (t = 2.74, df = 677.90, p = 0.006, d = 0.08), behavioural disengagement (t = 12.58, df = 660.97, p < 0.001, d = 0.65), venting (t = 5.21, df = 660.86, p < 0.001, d = 0.27), religion (t = 6.26, df = 655.67, p < 0.001, d = 0.33), and self-blame (t = 14.19, df = 628.77, p < 0.001, d = 0.76) and lower scores on active coping (t = 3.74, df = 2706, p < 0.001, d = 0.18) and planning (t = 2.42, df = 695.27, p = 0.016, d = 0.13) than the no-depression group.
Relationship between probable depression and demographics, anger, and coping strategies
The results of multiple logistic regression with J-PHQ-9 as the objective variables are shown in Additional Table
2. Demographics with ORs greater than 1 were having an underlying disease (OR = 1.96, 95% CI = 1.32–2.92,
p < 0.001), not working (OR = 1.85, 95% CI = 1.22–2.80,
p < 0.01), and experiencing a negative economic impact (OR = 1.33, 95% CI = 1.01–1.77,
p < 0.05), and demographics with ORs less than 1 were increased age (OR = 0.97, 95% CI = 0.96–0.98,
p < 0.001), being married (OR = 0.53, 95% CI = 0.38–0.74,
p < 0.001), and household income with more than 8 million JPY (OR = 0.45, 95% CI = 0.25–0.80). Both state anger and anger control had ORs greater than 1 (state anger: OR = 1.17, 95% CI = 1.14–1.21, p < 0.001; anger control: OR = 1.08, 95% CI = 1.04–1.13,
p < 0.001). Regarding coping strategies, the strategies with ORs greater than 1 were behavioural disengagement (OR = 1.28, 95% CI = 1.13–1.44,
p < 0.001) and self-blame (OR = 1.47, 95% CI = 1.31–1.65,
p < 0.001), and the strategies with ORs less than 1 were denial (OR = 0.88, 95% CI = 0.77–0.99,
p < 0.05), use of instrumental support (OR = 0.85, 95% CI = 0.76–0.95,
p < 0.01), and planning (OR = 0.84, 95% CI = 0.74–0.94,
p < 0.01). The OR for humour was less than 1 (OR = 0.89,
p < 0.05); however, the CI level included 1 (95% CI 0.80–1.00).