Physical activity (PA) is an important and potentially modifiable determinant of healthy ageing with positive effects on healthrelated quality of life [1]. It is often assumed that depression increases with age, but current epidemiological studies point to a lower prevalence of depressive disorder at higher age, compared to younger age patients [2]. Population-based studies have provided strong evidence that PA decreases the risk for depressive symptoms in younger [3] as well as in older adults [4]. As the majority of studies rely on (self-report) depressive symptom scales, it remains unknown whether these findings can be extrapolated to patients experiencing depressive disorder according to DSM-criteria [5,6]. To our knowledge, four longitudinal observational studies on the amount of PA in clinically depressed patients have been conducted in three different samples [7–۱۰]. Low PA as well as less sports activity predict unfavorable outcome of depression in depressed adults over time [7,10], with a reduction in the effect of low PA on depression outcome with increasing age up to 60 years [7]. In younger depressed adults, increasing levels of PA three weeks after admission was associated with decreasing levels of depressive symptoms [9]. Another sample of depressed patients aged 60 years and over, showed a lower level of PA during a depressive episode compared to their non-depressed counterparts [۱۱]. In this study, no relationship between PA and the course of the depressive disorder was observed over time [8]. These findings suggest there may be a moderating effect of age on the reciprocal association between PA and the course of a depressive disorder. PA might be useful as an (adjunct) intervention in the treatment of depressive disorder [12]. Meta-analyses on exercise interventions suggest that exercise may have a small, short term antidepressant effect in patients with depressive disorder [13]. However, it is also known that the most important preconditions for successful implementation of such interventions – participating and maintaining – are difficult to achieve, because of the nature of depressive disorder [14]. Interestingly, meta-regression showed that studies restricted to adults over 60 years of age showed a higher efficacy than those with subjects below 60 years [15].