Lithium and Other Elements in Scalp Hair of Residents of Tokyo Prefecture as Investigational Predictors of Suicide Risk

Abstract

The high suicide rates in Japan and several reports of inverse associations of suicide rates with the levels of lithium (Li) in drinking water prompted determinations of Li along with other elements in samples of scalp hair of 100 male and 100 female residents of Tokyo Prefecture. In more than half of the samples of both genders, Li levels were below the instrumental detection limit or below or the lower limit of the laboratory reference ranges. Among other elements, the concentrations namely of cobalt were also frequently below the laboratory reference range, suggesting that low circulating levels of vitamin B₁₂ were common in this study population. As vitamin B₁₂ deficiency is associated with depression and other psychiatric conditions, and there is evidence of interactions between Li and vitamin B₁₂, Li deficiency as well as suboptimal vitamin B₁₂ status must be considered as potential suicide risk factors. In view of its established positive effects on mood and brain function, an adequate supply of selenium (Se) is important as well. Although the analytical results suggested that the Se status of the subjects was generally adequate, as seafood was a major dietary source of Se, much of it was actually sequestered by mercury and only a fraction was bio-available. In addition, the hair samples were found to contain not insignificant levels of As, Cd, Ni, and Pb, arising from the adventitious presence of these elements in foods and the environment. As these elements also interact with Se in vivo and are known to adversely affect mood and behavior, in investigational studies, subjects at risk need to be evaluated also with respect to these elements.