Associations between ambient temperature and suicide: а systematic review

Background: Over the past 150 years, a large number of articles have been published around the world on the associations between ambient temperature and suicide. However, only in the last 30 years daily data with sufficient validity are in use, necessitating the systematization of the latest research evidence. Aim: To conduct a systematic selection and qualitative synthesis of published information on the associations between ambient air temperature and suicide over the past 30 years. Methods: A systematic review using PRISMA criteria. Studies published in peer-reviewed journals from January 1990 to April 2022 in PubMed and eLIBRARY in Russian or English, respectively, comprised the study base. The selection of articles was made according to the following criteria: original research; data on the ambient temperature in the studied period of time are presented and the upper part of the temperature range was studied; data on suicide counts are available. Results: Of the 1932 identified articles, 32 empirical studies with the number of cases ranging from 225 to 1067333 from 26 countries were included in the qualitative synthesis. In addition to mean temperatures, the minimum and maximum temperatures, as well as the calculated apparent mean, minimum and maximum temperature were used. By design, most studies had ecological or case-crossover design. Generalized Additive Models (GAM) were used as the main analytical tools, and in multicenter studies the results were obtained using meta-regression. The results were presented as relative risks or the percentage increase in the number of suicides with an increase in temperature by 1C. Virtually all studies reported a significant linear relationship between the temperature and suicide rates, but effect sizes varied between countries. The effect was more pronounced in temperate climate, in men and people over 65 years of age. Conclusions: Most of the studied suggest a direct relationship between high air temperature and the number of suicides in different latitudes. It is necessary to monitor the situation and study the mechanisms behind the associations between high temperatures and the risk of suicide to minimize the consequences of climate change for public health.