Type of study:Population-based birth cohort study

Annotation

The Findings: Working with a population-based birth cohort of about 4,750 individuals, those who confirmed having ever experienced suicidal ideation at age 16 (n=456) and those who endorsed having ever engaged in non-suicidal self-harm at age 16 (n=569) were identified and followed for transition to suicidal attempts by  age 21, five years later. Complete data outcome at 21 years of age were available for 310 of those who had experienced suicidal thoughts five years earlier, and 380 of those who had endorsed non-suicidal self-harm at age 16. In each of these groups, 12% (38 and 46 individuals, respectively) had attempted suicide by age 21. (Cohort members who had reported an initial suicide attempt by the age 16 were not included in the subsequent study group since the intent of the study was to identify factors associated with the transition from ideation and non-suicidal self-harm to a suicide attempt; the number  who had already attempted suicide at age 16 was 325.) Nearly 20 risk factors were examined for association with transition to suicide attempt at age 21. The three strongest predictors in the group who identified having had suicidal ideation at age 16 were non-suicidal self-harm, cannabis use, and other illicit drug use. Among those who endorsed non-suicidal self-harm at age 16, the three strongest predictors of transition to a suicide attempt were cannabis use, other illicit drug use, and sleep problems. Of the 107 study participants who reported both suicidal thoughts and non-suicidal self-harm at age 16, 22 (21%) reported having attempted suicide by age 21. By comparison, 1% of study participants who reported neither suicidal thoughts or non-suicidal self-harm at age 16 had attempted suicide by age 21.

Strengths and Weaknesses: This study is distinguished by its size and the longitudinal design which enabled prospective examination of multiple risk factors; the exclusion of individuals who had attempted suicide by the age of 16 enabled the authors to focus on factors associated with the transition from ideation and prior non-suicidal self-harm to suicide attempts. These strengths notwithstanding, the study illustrates associations, not cause-and-effect. Moreover, the follow-up interval of five years does not shed much light on factors that might predict transition to a suicide attempt in the short-run.

Relevance: Reported suicidal ideation is a frequent source of psychiatric consultation requests. The prominent association of cannabis use and other illicit drug use (but no evidence for association with alcohol use, incidentally) in the transition from ideation and non-suicidal self-harm to actual suicide attempts in adolescents and young adults underscores the value of including these risk factors in a psychiatric assessment. This may become increasingly important in the United States as the number of states where recreational use of marijuana is legalized increases.