Impact of loneliness on suicidal ideation during the COVID-19 pandemic: findings from a cross-sectional online survey in Japan

OBJECTIVES: We aim to reveal how loneliness relates to suicidal ideation following the onset of the COVID-19 pandemic. DESIGN: Cross-sectional online survey. SETTING: Community cohort study in Japan. PARTICIPANTS: The second wave of a large web-based survey, Japan COVID-19 and Society Internet Survey, was conducted in February 2021, and we analysed the data of 6436 men and 5380 women who were aged 20–59 years. MAIN OUTCOME MEASURES: The prevalence ratios (PRs) of suicidal ideation due to loneliness, depression, social isolation and decline in income during the pandemic and other sociodemographic and economic information were adjusted in the analysis. STATISTICAL METHODS: Estimations were conducted by separating a male and female sample. The survey weight (inverse probability weighting) was applied for analyses, and a Poisson regression model was used with all the potential confounders adjected. RESULTS: Overall, 15.1% of male and 16.3% of female participants were found to have had suicidal ideation during the COVID-19 pandemic. Among them, 23% of male and 20% of female participants experienced suicidal ideation for the first time. The results of the Poisson regression suggested that those who were feeling lonely had higher PRs for suicidal ideation (4.83 for men (95% CI, 3.87 to 6.16) and 6.19 for women (95% CI, 4.77 to 8.45)). The relationship between loneliness and suicidal ideation remained robust even after adjusting for depression, although there were declines in PRs. Additionally, the results showed that those who were lonely, and continued to feel lonely during the pandemic, had the highest PRs of suicidal ideation. CONCLUSION: Loneliness had both direct and indirect effects on suicidal ideation mediated through depression. Those who felt lonelier during the pandemic had the highest risk of suicidal ideation. It is necessary to adopt national measures focused on providing psychological support to people who feel lonely to prevent them from taking their own lives.