Admixture analysis of age at first suicide attempt

Clinical and familial studies have suggested that age at first suicide attempt (SA) is a marker for different subtypes of suicidal behaviors. However, none of the various thresholds used to define subgroups according to the age at first suicide attempt have been validated. The aim of this study was to try to define different subgroups according to age at first SA subtypes using admixture analysis.

In a sample of 368 consecutively recruited patients from Sept. 2001 to Sept. 2005 with a personal history of suicide attempt, admixture analysis was used to determine the best-fitting model for the observed distribution of age at first SA.

The theoretical model that best explains the observed distribution of age at first SA was a mixture of two Gaussian distributions with mean ages (+/-SD) of 19.5 +/- 4.3 and 38.5 +/- 12.4 years with a cut-off point of 26 years for the two subgroups. In multivariate analyses, the early onset subgroup was characterized by more frequent comorbid anxiety disorders, cannabis misuse and personal history of emotional and sexual abuse. Patients belonging to the late onset subgroup were more likely to suffer from major depressive disorders (single or recurrent).

This study provides a mathematical modelisation suggesting the existence of two age at onset subgroups in suicidal behaviors with different clinical picture and history of childhood trauma. Given the heterogeneity of suicidal behavior, these results suggest that the age at first SA may represent a valid 'candidate symptom' for future investigations of vulnerability factors.