Affect dynamics reflect individual differences in how emotional information is processed, and may provide insights into how depressive episodes develop. To extend prior studies that examined affect dynamics in currently depressed individuals, the present study tested in 68 nondepressed young adults whether three well-established risk factors for major depressive disorder (MDD) -(a) past episodes of MDD, (b) family history of MDD, and (c) reduced neurophysiological responses to reward -predicted mean levels, instability, or inertia (i.e., inflexibility) of positive affect (PA) and/or negative affect (NA). Momentary PA and NA were assessed up to 6 times per day for 14 days (mean number of surveys completed=45.89). MDD history and family history of MDD were assessed via semi-structured interview, and neurophysiological responses to reward were indexed using the Reward Positivity, an eventrelated potential related to depression. After adjusting for current depressive symptoms, results indicated that (a) past episodes of MDD predicted higher mean levels of NA, (b) family history of MDD predicted greater PA inertia, and (c) blunted reactivity to reward predicted greater NA inertia. Collectively, these results suggest that elevated mean levels of NA and inflexibility of PA and NA may be potential mechanisms that confer risk for depression.

Background During adolescence, peer support has an increasingly important role in identity formation and well‐being. Prior research has identified that lack of social support from peers in adolescence is a potent risk factor for depression. Two ways that social support has been operationalized is by the number of one's friends (i.e., ‘quantity’) and perception of one's network (i.e., ‘quality’). Typically, these aspects of peer support are assessed separately. Methods Using data from the National Longitudinal Study of Adolescent to Adult Health (N = 3,857), this study sought to test whether (1) adolescent depression relates to having fewer friends versus lower quality friendships, (2) these aspects of adolescent peer support prospectively predict depression in adulthood, (3) gender moderates the effects of peer support on depression, and (4) these aspects of peer support buffer the effects of stressful life events on depression. Results Peer support quality uniquely predicted depression in adolescence and adulthood among both males and females. The effect of peer support quality on depressive symptoms, however, was greater for females than males. By contrast, peer support quantity did not uniquely predict depression for males or females. Conclusions Qualitative aspects of adolescent peer support uniquely contribute to mental health not only in adolescence, but in adulthood as well. Potential processes through which peer support relates to depression are discussed, as well as implications for treatment.