Voshaar RCO, Dimitriadis M, van den Brink RHS, et al. - In view of the conceptualisation that depressive disorder is a condition of accelerated biological ageing, researchers herein operationalized a frailty index (FI) as marker for biological ageing with the aim to explore the bidirectional, longitudinal association between frailty and either depressive symptoms or depressive disorder. In this cohort study, 377 older (≥ 60 years) outpatients with a DSM-IV defined depressive disorder and 132 never-depressed controls with 6-year follow-up were included. Frailty likely confounds the sum score of depression rating scales. Accelerated biological ageing was observed in correlation with depressive disorder according to DSM-IV criteria. This argues for generating multidisciplinary geriatric care models integrating frailty to improve the overall outcome of late-life depression.