The purpose of this study was to evaluate whether elements signifying relative insulin sensitivity (IS) were prospectively linked to accidents and suicides in 14,976 Helsinki Heart Study (HHS) screenees. The main outcome measure was hospitalizations and deaths from accidents and suicide attempts determined from Finnish registries, in aggregate; and separating out suicides (and attempts). Cox proportional hazards regression was used to determine adjusted risk ratios (RR) relating IS characteristics (extreme quartiles of high HDL-C, low BMI, and low SBP), individually and conjointly, to subsequent accidents or suicides (including attempts), adjusted for age, alcohol use, smoking, and non-HDL cholesterol. Each IS element was related to combined hospitalization and death, from accidents and from suicide attempts; increasing numbers of these characteristics were associated with increased risk, an effect that was more powerful and statistically significant for suicide. For accidents, the presence of one and two to three IS characteristics provided RRs (95% confidence intervals (CI)) of 1.08 (0.97-1.20) and 1.14 (0.98-1.31), respectively. For suicides including attempts, RRs (95%CI) were 1.61 (1.09-2.38) for one IS factor, and 1.88 (1.18-2.98) for two to three IS factors, while for completed suicides, the figures were 2.01 (1.19-3.38) and 2.24 (1.20-4.17), respectively. We speculate that insulin sensitivity may relate to these outcomes through low central serotonin activity.