Psychosocial and neurocognitive correlates of suicidal thoughts and behaviours amongst siblings of persons with and without neurodevelopmental conditions

Objective: Siblings of individuals with neurodevelopmental conditions (NDCs) have greater incidence of neuropsychiatric diagnoses and neurocognitive difficulties compared to siblings of persons without NDCs. Despite suicidality being labelled a global health crisis (WHO, 2014) and NDC siblings experiencing risk factors implicated in suicidality, no previous studies examined suicidality amongst adolescent and young adult siblings of persons with NDCs. Our study aimed to bridge this gap. Method: The present study used Bayesian analyses and risk classification models to examine individual and environmental risk factors associated with suicidal thoughts and behaviours amongst siblings of persons with and without NDCs (n = 267; 132 NDC, 135 control group, mean age 20.61, range 14-27, 76.40% female, 76.78% White Caucasian), as measured using self-report survey data and remote self-administered cognitive tests. Results: NDC siblings had higher rates of current nonsuicidal self-injury (NSSI; 18.94% versus 14.07%, 8 = -0.32), suicidal ideation (25.76% versus 8.89%, 8 = -0.40) and history of suicide attempts (18.18% versus 4.44%, 8 = -0.43) compared to controls. Classification models using boosting and random forest demonstrated adequate performance: positive predictive value 0.86-0.91, negative predictive value 0.81-0.90, false negative rates 0.11-0.24. Cognitive inflexibility, alexithymia, inattention, bullying, depression, NSSI, and eating or psychotic disorder history had the highest relative importance in predicting lifetime suicidality. Poorer executive functioning (measured by the Wisconsin Card Sorting Task, Sustained Attention to Response Task, Stop Signal Task, and N-Back 2-back task) was strongly correlated with suicidality. Conclusions: Screening for proximal and modifiable risk factors is critical to inform suicidal behaviour intervention and prevention programs for at-risk siblings.