Preventing mental health problems in children after high conflict parental separation/divorce study: An optimization randomized controlled trial protocol

•Interparental conflict amplifies the risk of adverse consequences associated with children's parental separation/divorce experience. There is a pressing need for effective interventions to reduce such risk.•Effective, affordable, scalable, and efficient interventions have the greatest public health impact. Optimized interventions include only active components for best-expected outcomes under real-world implementation constraints.•Adaptive coping mitigates the effects of stressors on children's outcomes but assessing “goodness-of-fit” is needed to identify effective coping strategies for particular contexts.•Effective interventions that preserve children's emotional security and coping efficacy hold promise for protecting their long-term mental health.