Temporal Analysis of a Japanese Online Forum for Suicide Risk Monitoring

Background : Suicide prevention can be significantly enhanced by time-sensitive surveillance using digital data sources like online forums. To inform more effective suicide prevention strategies, this study analyzes the temporal patterns of posts on a Japanese mental health forum—the NHK “Facing Suicide” forum—that may aid in early risk detection. Methods : We analyzed 63,046 posts from Japan’s national broadcaster (NHK) forum (Jan 1, 2008–Mar 31, 2025), stratified by sex and age (≤ 19, 20s, 30s, ≥ 40). Generalized additive models were used to model hourly, weekly, and monthly variations, with time included as a spline term. Results are presented as incidence rate ratios (IRRs) with 95% confidence intervals (CIs). Results : Females contributed 75.5% of posts, and the 20–29 age group was the most active (32.4%). Posting activity consistently peaked around 23:00 across all subgroups. A marked increase was observed among adolescents (≤ 19) in August (males: IRR = 1.30, 95% CI [1.05–1.61]; females: IRR = 1.55, 95% CI [1.43–1.69]), while adults showed decreases in January–February. Weekly patterns varied by subgroup; for instance, males aged 20–29 posted more on Mondays and Tuesdays (IRR = 1.17, 95% CI [1.05–1.30]). Conclusions : Online forum activity displays predictable temporal cycles with demographic-specific patterns. These findings provide an essential baseline for real-time systems to detect deviations that may signal elevated suicide risk. The August peak in adolescent posts aligns with back-to-school distress, and the late-night peaks underscore the need for 24-hour support services. These insights can guide the development of targeted, time-sensitive suicide prevention strategies.