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1. Introduction
Suicide attempts (SA) represent a major public health problem with a lifetime prevalence ranging between 1.1% [1] and 5.9% [2]. Suicidal behavior (death and attempts) is frequently a complication of psychiatric diagnoses [3]. However, there is increasing evidence that suicidal behavior exists independently from major psychiatric disorders [4–6]. Indeed, it has recently been suggested that suicidal behavior should be considered a separate diagnostic category apart from major psychiatric conditions [7]. Because a SA is one of the most compelling predictors of completed suicide, an optimal categorization of suicide attempters may serve to improve current suicide prevention and intervention policies [8, 9].
Some studies have documented that younger age at first SA is strongly associated with higher rates of family history of suicidal behavior [10] and childhood risk factors [11, 12]. Also, life events preceding SA have been found to vary depending on the age of the first SA. A study by Heikkinen et al. [13] found physical-and social-related problems becoming more prominent and employment and financial problems less prominent with increasing age. Age at onset (AAO) of SA may aid in delineating disorder subtypes of suicidal behavior [10, 12, 13] and diminish heterogeneity [14]. The definition of clear-cut phenotypes is critical to establish the genetic underpinnings of complex behaviors such as suicidal behavior [15, 16]. Precise delineation of subtypes of SA will facilitate future research on the course, family transmission, pathophysiology, and treatment responsiveness of suicide attempters. In addition, an adequate understanding of AAO is essential for implementing prevention of psychiatric disorders, including suicidal behaviors [17]. To date, only one threshold to differentiate subgroups according to the AAO in SA has been proposed. Recently, Slama et al. [18] found that the theoretical model that best explained the distribution of age at first SA was a mixture of two Gaussian distributions with a cut-off point of 26 years old. Those in the younger group were found to be more likely to have anxiety disorders, cannabis misuse, and a history of childhood emotional and physical abuse, but less likely to present major depressive disorder.
Sex, as well as age, has been widely recognized as a sociodemographic correlate significantly associated with SA [19]. Despite obvious differences in prevalence, rates of psychiatric disorders, lethality of attempts...