Depression trajectories from mid to late life (50-89 Years): The roles of cohort, multimorbidity status, and national contexts across nine European countries

OBJECTIVES: This study aims to disentangle the age and cohort effects on depressive symptoms among middle-aged and older adults, while accounting for the role of multimorbidity across nine European countries. METHODS: Using longitudinal data from the Survey of Health, Ageing, and Retirement in Europe (SHARE) (2004-2022), with participants aged 50-89 and birth cohorts from 1921 to 1970, we employed Hierarchical Age-Period-Cohort (HAPC)-Growth Curve models to estimate age and cohort effects on depressive symptoms. Interaction effects of multimorbidity and country with cohort and age were also tested. Bounding analysis was used as a robustness check. RESULTS: The age effect revealed a U-shaped trajectory of depressive symptoms, with a decline after age 50, reaching a low point around age 65, followed by a sharp increase after age 70. The cohort effect showed that later-born cohorts experienced higher levels of depression. Bounding analysis confirmed these findings: period effects were near zero, with the exception of Spain. Multimorbidity was positively associated with depression, with significant national differences. Younger cohorts with multimorbidity status in Scandinavian countries show elevated depressive symptoms. For Spain, depressive symptoms are concentrated among earlier-born cohorts. Central European countries showed variability, but Germany's depression trajectory remained stable, with cohort effects being most pronounced. DISCUSSION: Our findings emphasize the need for a life-course perspective to understand depression trajectories. Cohort differences highlight the role of sociohistorical contexts, while multimorbidity requires attention in long-term healthcare policy.