This dissertation research will examine the joint contributions of childhood environment and family background factors, traumatic events, and genetic effects to the development of depression, panic attacks, and panic disorder using a genetically informative sample of twins. Exploration of the interplay between genes and environment can be an important tool for intervention research. Identifying developmental stages where environmental factors can have the greatest effect on later expression of disorder can aid in identification of more precise and potentially effective points for early prevention or intervention efforts. The aims of this proposal are (1) to examine associations between early trauma exposure and development of depression, considering effects of gender, type of trauma, and age at first trauma, (2) to identify family background factors associated with increased risk of early trauma exposure, and to determine contributions of early trauma exposure and correlated family background factors to risk for depression, (3) to examine the joint contributions of trauma, family background factors, and genetic effects on risk for depression, (4) to examine the differential effects of family background factors, traumatic events, and genetic effects on risk for depression, panic attacks, and panic disorder. [unreadable] [unreadable]