Four studies tested a theory that high interparental conflict increases child mental health risk by shaking children's sense of security in the family. Findings showed that children's fear, avoidance, and involvement were prominent responses, especially relative to reactions predicted by other theories. Interparental conflict related to greater child insecurity. Insecurity related to greater mental health difficulties even when considering previous mental health, child's perceptions of conflict, and parent-child relationship. (Author/KB)