Rumination is a maladaptive form of emotion regulation and seems to be the cognitive mechanism linking stress to depressive symptoms. However, it remains to be investigated whether individuals' variation in rumination in relation to the occurrence of stressful events (e.g., phasic co-variation between stressful events and rumination) prospectively predict the experience of depressive symptoms in lengthy follow-up moments. In this eighteen months prospective design, a large unselected sample of undergraduates was tested before, during, and after a period with prominent naturally occurring stressful events. The multilevel results show that the co-variation of stressful events and ruminative thinking predicts the experience of depressive symptoms at 3 and 15 months follow up moments, also when statistically controlling for baseline depressive symptoms. Moreover, the data demonstrate that the phasic elevations of rumination in relation to the occurrence of stressful events are more predictive of depressive symptoms compared with the stable aspects of rumination measured at one occasion. At the clinical level, the current findings seem to suggest a process-oriented intervention to target the phasic ruminative cognitions where individuals need to learn to control rumination exactly at moments of stress.
Keywords: Stressful events, rumination, depressive symptoms, prospective design3 Stressful life-events are known to initiate negative, self focused thoughts, rendering individuals vulnerable for depression (e.g., for a review, see Monroe, Slavich, & Georgiades, 2014). In the processing of these stress-induced negative cognitions, depressive ruminationpassively and repetitively contemplating symptoms and consequences of distress (NolenHoeksema, 1991;2000) -is considered a key mechanism of action. Although individuals often ruminate to understand negative feelings and problems, rumination does not enhance clarity and instead has detrimental effects on emotional well-being (Nolen-Hoeksema, Luybomirski, & Wisco, 2008). Considerable empirical support has shown that rumination is a maladaptive form of emotion regulation and has linked this thinking style to numerous maladaptive outcomes (e.g., Nolen-Hoeksema, 1991). Indeed, if these abstract and selfevaluative cognitions regarding the symptoms of distress are recursively activated and rehearsed, symptoms of distress are likely to be maintained (rather than overcome) and become depressogenic (Robinson & Alloy, 2003; Papageorgiou & Wells, 2004;Watkins & Nolen-Hoeksema, 2014). Therefore, rumination may be a cognitive mechanism that mediates the association between stress and depressive symptoms/depression (Ruscio et al., 2015).Even though many theoretical models exist, the principal theory on depressive rumination is the Responses Styles Theory (RST; Nolen-Hoeksema, 1991), which hypothesizes that depressive rumination is a stable and habitual, trait-like tendency to engage in repetitive selffocused thoughts in response to depressed mood (see Nolen-Hoeksema et al., 2008)...