This chapter examines five issues of childhood and adolescent depression that consider the interplay between continuity and risk. The first focuses on the rate of various forms of depression in the childhood and adolescence years. The second tracks the physiological concomitants and possible predictors of depression among the physiological changes that characterize early adolescence. The third is regarding the timing and sequencing of biopsychosocial changes in the first half of adolescence. The fourth concerns family history and rearing environment. Finally the fifth looks at what is known about continuity between clinical depression and less severe forms of depressed affect, especially as the study of physiological processes might shed light on this most important aspect of continuity. Research suggests that a high degree of comorbidity occurs between depression and other mental disorders and research on psychological mechanisms considers both clinical depression and depressed affect.