Predictors of future suicide attempt among adolescents with suicidal thoughts or non-suicidal self-harm: a population-based birth cohort study

Background Suicidal thoughts and non-suicidal self-harm are common in adolescents and are strongly associated with suicide attempts. We aimed to identify predictors of future suicide attempts in these high-risk groups. Methods Participants were from the Avon Longitudinal Study of Parents and Children, a population-based birth cohort study in the UK. The sample included 456 adolescents who reported suicidal thoughts and 569 who reported non-suicidal self-harm at 16 years of age. Logistic regression analyses were used to explore associations between a wide range of prospectively recorded risk factors and future suicide attempts, assessed at the age of 21 years. Findings 38 (12%) of 310 participants with suicidal thoughts and 46 (12%) of 380 participants who had engaged in non-suicidal self-harm reported having attempted suicide for the first time by the follow-up at 21 years of age. Among participants with suicidal thoughts, the strongest predictors of transition to attempts were non-suicidal self-harm (odds ratio [OR] 2.78, 95% CI 1.35-5.74; p=0.0059), cannabis use (2.61, 1.11-6.14; p=0.029), other illicit drug use (2.47, 1.02-5.96; p=0.045), exposure to self-harm (family 2.03, 0.93-4.44, p=0.076; friend 1.85, 0.93-3.69, p=0.081), and higher levels of the personality type intellect/openness (1.62, 1.06-2.46; p=0.025). Among participants with non-suicidal self-harm at baseline, the strongest predictors were cannabis use (OR 2.14, 95% CI 1.04-4.41; p=0.038), other illicit drug use (2.17, 1.10-4.27; p=0.025), sleep problems (waking in the night 1.91, 0.95-3.84, p=0.069; insufficient sleep 1.97, 1.02-3.81, p=0.043), and lower levels of the personality type extraversion (0.71, 0.49-1.03; p=0.068). Interpretation Most adolescents who think about suicide or engage in non-suicidal self-harm will not make an attempt on their life. Many commonly cited risk factors were not associated with transition to suicide attempt among these high-risk groups. Our findings suggest that asking about substance use, non-suicidal self-harm, sleep, personality traits, and exposure to self-harm could inform risk assessments, and might help clinicians to identify which adolescents are at greatest risk of attempting suicide in the future. Funding American Foundation for Suicide Prevention, National Institute for Health Research Biomedical Research Centre at the University Hospitals Bristol National Health Service Foundation Trust, and the University of Bristol. Copyright (c) The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.