Development of severe psychological distress among low-income individuals during the COVID-19 pandemic: longitudinal study

BACKGROUND It has been indicated that the health impact of COVID-19 is potentially greater in individuals from lower socioeconomic status than in the overall population. AIMS To examine how the spread of COVID-19 has altered the general public's mental health, and whether such changes differ in relation to individual income. METHOD An online longitudinal survey was conducted at three different time periods during the pandemic. We recruited 1993 people aged 20-70 years, living in the Tokyo metropolitan area in Japan. Participants' mental health was measured with the six-item version of the Kessler Psychological Distress Scale; the existence of severe psychological distress was ascertained through the cut-off data. Multiple logistic and mixed-model ordinal logistic regression analyses were performed, with income as the independent variable. RESULTS Of the participants, 985 were male, with a mean age of 50.5 (±15.8) years. Severe psychological distress percentages for each tested period were 9.3%, 11.2% and 10.7% for phases 1, 2 and 3, respectively. Between phases 1 and 2 or phases 2 and 3, the group that earned <£15 000 had significantly higher propensity to develop severe psychological distress than the group that earned ≥£45 000 (odds ratio 2.09, 95% CI 0.95-4.56 between phases 1 and 2; odds ratio 3.00, 95% CI 1.01-9.58 between phases 2 and 3). CONCLUSIONS Although there has been significant deterioration in mental health among citizens during the COVID-19 pandemic, this was more significant among those with lower income. Therefore, mental health measures that focus on low socioeconomic groups may be necessary.