In adulthood, twice as many women as men are depressed, a pattern that holds in most nations. In childhood, girls are no more depressed than boys, but more girls than boys are depressed by ages 13 to 15. Although many influences on this emergent gender difference in depression have been proposed, a truly integrated, developmental model is lacking. The authors propose a model that integrates affective (emotional reactivity), biological (genetic vulnerability, pubertal hormones, pubertal timing and development) and cognitive (cognitive style, objectified body consciousness, rumination) factors as vulnerabilities to depression that, in interaction with negative life events, heighten girls' rates of depression beginning in adolescence and account for the gender difference in depression.