Life event trajectories and suicidal ideation throughout adolescence: a prospective cohort study from Germany, France, Ireland, and the UK

Background Adolescence is a sensitive period when suicidal ideation can peak. Although traumatic life events are a well established risk factor for suicidal ideation, the role of cumulative ordinary life events across multiple dimensions, such as family, autonomy, and sexuality, remains underexplored. Crucially, no evidence is available on how multidimensional trajectories of cumulative exposure to such events relate to suicidal ideation throughout adolescence. We aimed to examine how cumulative and domain-specific trajectories of ordinary life events during adolescence relate to suicidal ideation. Methods In this multinational, prospective cohort study, we used longitudinal data from the IMAGEN cohort, gathered from eight centres in Germany, France, Ireland, and the UK between January, 2008, and January, 2010, to model trajectories of exposure to life events during adolescence, and to quantify the association between trajectory group and suicidal ideation. Participants were assessed at ages 14, 16, 19, and 23 years, and key inclusion criteria included having the capacity to provide informed assent or consent, and having parental completion of perinatal and developmental history. Exposure to 39 life events across seven dimensions (family, accidents, distress, autonomy, deviance, sexuality, and relocation) were assessed using the Life Events Questionnaire (LEQ), administered at each of the study timepoints. Childhood maltreatment was also assessed, using the Childhood Trauma Questionnaire, administered once at age 19 years. The primary outcome was the number of participants with suicidal ideation across trajectories, assessed via a dedicated item in the LEQ at the first three timepoints. We also compared self-harm and suicidal ideation responses from the Developmental and Well-Being Assessment at the first three timepoints. Latent trajectory analysis was used to identify classes of cumulative life event exposure across repeated assessments: high, mid-high, mid-low, and low. The association between trajectory group and suicidal ideation was quantified using logistic mixed model regressions, adjusting for childhood maltreatment and demographic covariates. No individuals with lived experience of suicidality or mental health conditions were involved in the design, conduct, or reporting of this research. Findings At baseline, 2161 adolescents, enrolled between January, 2008, and January, 2010, were included in the cohort (1106 [51·2%] female and 1055 [48·8%] male). Sample sizes at subsequent waves were 1581 at first follow-up (which took place between January, 2011, and January, 2012), 1474 at second follow-up (between January, 2013, and January, 2015), and 1331 at third follow-up (between January, 2016, and January, 2019). At each timepoint, the high trajectory group (1125 [52·1%] of 2161 participants) had the highest proportion of participants with suicidal ideation (90 [8·0%] of 1125 at pre-baseline, 127 [11·3%] of 1125 at age 14 years, 102 [13·4%] of 759 at age 16 years, and 78 [11·0%] of 709 at age 19 years). After controlling for demographics and childhood maltreatment, the high trajectory group had the highest predicted probability of suicidal ideation at each timepoint. Life events in the family dimension predicted adolescent suicidal ideation (marginal R 2 GLMM =0·078) more than those in all remaining dimensions combined (marginal R 2 GLMM =0·073). Interpretation We found that higher cumulative exposure to ordinary life events across multiple dimensions is associated with higher suicidal ideation in adolescence, with life events occurring within the family environment carrying the highest risk. These results point to the importance of evaluating different types of everyday life event exposure, not just childhood trauma or maltreatment, when assessing suicidal risk in adolescents. Funding Abroad Advanced Study Fellowship, Chang Gung Medical Foundation, Taiwan; National Science and Technology Council, Taiwan; Medical Research Council, UK.