Seasonal variations in suicide mortality in Canada: A nationwide analysis

OBJECTIVE: To investigate the seasonality of suicide mortality in Canada and explore differences across sex and age. METHODS: We analyzed monthly suicide deaths spanning January 2001 to December 2015 from the Canadian Vital Statistics Death Database. Data from 2016 onwards were not included in the main analysis as Ontario and Yukon data were unavailable due to data-sharing agreement limitations. However, data from 2016-2019 were included in the sensitivity analyses. Seasonal variations were assessed by evaluating the timing of peak and trough monthly suicide mortality rates, and amplitude (peak-to-trough risk ratio) overall and by sex and age groups. Statistical significance was tested using the Seasonal Autoregressive Integrated Moving Average procedure. RESULTS: With 40,405 recorded suicides, results indicated a peak in suicide rates in July (0.95 per 100,000 people), 6.74% higher than the monthly average, and a trough in February (0.78 per 100,000 people), 12.36% lower than the monthly average. The peak/trough relative risk (RR) was 1.22 (95% CI: 1.00, 1.47). Seasonality patterns were similar between sexes, but stronger and more stable among males. Seasonality patterns were similar across age groups, but the amplitude was larger among those aged 65+. CONCLUSIONS: This study confirms seasonal patterns in suicide mortality in Canada, peaking during the summer months. Such patterns are more prominent and stable among males, and its amplitude was larger among older adults. Contrary to the common perception that suicide rates peak in January, our findings show a summer peak. Future research should explore the underlying mechanisms driving these seasonal variations and their demographic differences.