Longitudinal trajectories of depression across adolescence, emerging adulthood and adulthood: findings from the National Longitudinal Study of Adolescent to Adult Health (Add Health) (1994-2008).

Background: The heterogeneity of depression is well documented. Considering the Life Course Theory, longitudinal analysis establishing trajectories may demonstrate the stability and variation of depression. Methods: Data from four waves of the National Longitudinal Study of Adolescent to Adult Health (Add Health) were used to investigate depression trajectories. Nine items from the Center for Epidemiological Studies (CES-D) measured depression of 9421 participants. Trajectories were established using growth mixture modelling (GMM) and multinomial regression was employed to explore the influence of gender and ethnicity. Results: Five distinct and unique trajectories were established as minimal (66.8%), moderate (19.1%), Emerging Adulthood (EA) trough (7.6%), persistently high (3.3%) and EA peak (3.1%). Being female and non-white increased the probability of being in the elevated trajectories during adolescence. Conclusion: Three stable and two fluctuating trajectories demonstrate both the predictability and heterogeneity of depression across three distinct developmental stages.