A prospective study of the paradoxical relationship between impulsivity and lethality of suicide attempts

Background: Biological studies suggest that lower serotonergic activity is associated with both greater suicide lethality and impulsive personality tr aits. These results may lead to the conclusion that impulsivity in the atte mpt should be associated with greater lethality. However, Klerman's review of epiderniologic suicide studies suggests an inverse relationship between impulsivity and lethality. This seemingly paradoxical relationship between impulsivity and lethality has not been explored in large representative cli nical samples of suicide attempts. Method. During 1996 to 1998, 478 individuals who attempted suicide were stu died in a general hospital in Madrid, Spain. Impulsivity was measured as de scribed in the literature by combining 2 items of Beck's Suicidal Intent Sc ale (active preparation for attempt and degree of premeditation). Lethality of the attempt was assigned 1 of 4 levels according to the need for medica l and/or psychiatric treatment. Results: More than half of the attempts were impulsive (55%; 95% confidence interval [CI], 51% to 59%), approximately one fourth of the attempts had a n intermediate level of impulsivity (28%; 95% CI, 24% to 3.2%), and approxi mately one sixth of the attempts were not impulsive (17%,95% CI, 13% to 2 1 %). There was an inverse association between the impulsivity and lethality of the suicide attempt chi (2) = 62.639, df = 6, p < .0001). The most impul sive attempts tended to result in less morbidity, while the less impulsive attempts tended to be more lethal. Conclusion: If the inverse relationship between impulsivity and lethality i s replicated in other large and representative samples, new studies will be needed to clarify the complex interactions between the clinical dimensions (lethality, impulsivity as a state, and impulsivity as a personality trait ) and the biological correlates (particularly serotonergic function) of sui cidal behavior.