Stability and change in self-reported risk and resilience factors associated with mental health of siblings of individuals with and without neurodevelopmental conditions over 15 months

Background: Siblings of individuals with neurodevelopmental conditions (NDCs) are a minority population at higher genetic and environmental risk of poorer neurocognitive and psychosocial outcomes compared to siblings of individuals without NDCs. Method: Measured over a 15-month interval between 2021 and 2022, the present prospective follow-up study is the first Bayesian examination of the unique relationships between self-reported modifiable individual-level risk, resilience, and neuropsychiatric variables amongst siblings of persons with (n = 134) and without (n = 143) NDCs (mean age 22.42, range 9–38 years, 75.81% female, 79.78% White Caucasian). Results: The NDC group maintained elevated rates of self-reported mental health diagnoses at follow-up (effect size δ −0.57), with greater risk and fewer resilience variables than controls (δ ranging 0.50–1.07). The NDC group demonstrated group-level worsening of depression (δ −0.32). At the participant level, NDC siblings had statistically reliable declines in executive functioning and self-regulation (anxiety, empathy, attention, cognitive reappraisal) compared to the controls. Baseline self-reported sleep difficulties strongly predicted both depression and anxiety at follow-up for NDC siblings. Life events had minimal impact on mental health outcomes. Implications: Findings suggest the clinical utility of interventions for NDC siblings could be improved with a multi-modal approach, and monitoring and targeting changes in transdiagnostic risk factors contributing to poorer mental health.