Comparison of lithium levels between suicide and non-suicide fatalities: cross-sectional study

IntroductionEcological studies have suggested the protective effect of micro-dose lithium in drinking water against suicide, however, the association between body lithium level and suicide is unknown.ObjectivesWe aimed to compare body lithium levels between suicide and non-suicide fatalities.MethodsThis cross-sectional study included 12 suicides and 16 non-suicides who were examined or dissected at the Tokyo Medical Examiner’s Office from March 2018 to June 2021. The aqueous humor lithium concentration was measured twice using inductively coupled plasma mass spectrometry. Analysis of covariance (ANCOVA) was used to compare the lithium concentration between suicides and non-suicides. Mixed-effects model was conducted to account for all lithium concentration data.ResultsThe aqueous humor lithium concentration did not change after death (t(7)=-0.70, SE=0.03, 95% CI=[-0.09, 0.05], P=0.51, Cohen’s d=0.01). The aqueous humor lithium concentration was lower in suicides (mean 0.50 μg/L (variance s2 0.04)) than in non-suicides (mean 0.92 μg/L (s2 0.07)) (t(26)=4.47, SE=0.09, 95% CI=[0.22 to 0.61], P