The tendency to appraise naturally occurring life events (LEs) as having high negative impact may be a predisposing factor for the development of depression and anxiety disorders. In the current study, appraisals of the negative impact of recent LEs were examined in relationship to depressive and anxiety disorders in a sample of 653 adolescents who were administered diagnostic and life stress interviews at ages 15 and 20. Participants' appraisals of the negative impact of LEs reported at age 15 were statistically adjusted using investigator-based ratings to control for objective differences across LEs. Higher appraisals of the negative impact of LEs were associated with both past and current depressive and anxiety disorders at age 15 and predicted subsequent first onsets of depressive and anxiety disorders occurring between ages 15 and 20. In addition, appraisals of the negative impact of LEs were particularly elevated among those experiencing both a depressive and anxiety disorder over the course of the study. The findings suggest that systematically elevated appraisals of the negative impact of LEs are a predisposing factor for depression and anxiety disorders and may represent a specific risk factor for co-morbid depression and anxiety in mid-adolescence and early adulthood.