Inverse relationship between lithium levels in drinking water and suicide rates

Abstract

Introduction: Suicide is an important public health problem in Lithuania and around the world. Lithuania ranks fourth in the world’s suicide rate, while it has a second rank for the male suicide rate among all countries in the world [1]. Although suicide rate in Lithuania declined over the past few years from 30 suicides per population of 100,000 in 2015 to 28.3 in 2016 and 26 in 2017, the overall number of people taking their own lives remains rather high [2]. The findings across geographical regions provided evidence that higher lithium levels in the public drinking water may be associated with lower suicide rates [3,4,5]. Studies of environmental and neurobiological factors which may increase or decrease suicide risk may lead to a development of new suicide prevention methods. Aim: To investigate an association of lithium levels in drinking water with suicide mortality rates in Lithuania. Methods: Fifty-six samples from public drinking water systems were taken in all 54 districts municipalities of Lithuania. Lithium levels were determined using the ion chromatography method. For the statistical calculations, lithium levels were averaged per district municipality and plotted against suicide standardized mortality rates (SMR) per 100,000 populations, within the 5-year period from 2012 to 2016. In accordance with the International Statistical Classification of Diseases (ICD-10) we considered only suicide attempts that resulted in death with the ICD-10 codes from X60 to X84. Data on potential confounding factors of suicide risk that included unemployed rate, number of visits to psychiatrist, divorce rate, female/male proportion (number of females per 1000 males) were obtained from the Department of Statistics, and were averaged across the investigated time period. Results: The mean lithium concentration in 56 drinking water samples was 11.5 (SD 9.9) μg/L ranging from 1.0 to 39.0 μg/L, median – 7.0 (IQR 3. [...].