Unraveling co-rumination: Extensive discussion of problems may have a negative impact on adolescent emotional adjustment

Depressive symptoms dramatically increase in the transition from childhood to adolescence (Hankin et al., 1998). Although friendships provide an important source of social support in this period and can protect youth against emotional problems (Bukowski et al., 1996), some characteristics of friendships may actually increase levels of depression rather than protect against such symptoms. Co-rumination, or excessively discussing personal problems within a dyadic relationship (Rose, 2002), has been found disadvantageous for emotional wellbeing, while also promoting friendship quality and closeness among best friends. The current dissertation aims to extend past research on co-rumination in several ways.

First, although co-rumination is understood as the interpersonal form of rumination, no study hitherto has explored whether the intrapersonal rumination components ‘brooding’ and ‘reflection’ (Treynor et al., 2003), also apply to an interpersonal context. In the first two papers with 2- and 3-month intervals, we distinguished co-brooding from co-reflection and studied relations with outcomes. Interpersonal brooding was found to be maladaptive, predicting higher concurrent and prospective depressive symptoms in girls. Interpersonal reflection predicted less depressive symptoms in girls and higher concurrent friendship quality, and was thereby understood as adaptive. Second, although the relation between co-rumination and depressive symptoms has frequently been established, knowledge on its underlying mechanisms is scarce. The third paper investigated intrapersonal rumination as a mediator in this relation. An indirect effect was established, with co-rumination predicting relative increases in levels of depressive symptoms after two years, through rumination. No evidence was obtained for relations with co-rumination in opposite directions. Third, inconsistent findings on relations between co-rumination and depressive symptoms raise the question of possible interaction effects. The fourth paper investigated co-rumination from a vulnerability-stress perspective and studied whether it acts as a potentiating factor strengthening the associations between stress and depression. Girls high on co-rumination but boys low on co-rumination reported higher levels of depressive symptoms in the context of interpersonal stress across a one-year period. Fourth, although co-rumination has been shown to be maladaptive for emotional well-being, research on the antecedents of co-rumination is lacking. The fifth paper aimed to gain insight into who may be (more) prone to co-ruminate by studying temperament and attachment as two predictors of co-rumination trajectories. Higher positive affectivity, higher trust in the availability of a mother, and higher attachment anxiety were found to predict higher co-rumination in boys and girls. Higher effortful control and lower attachment avoidance related to higher co-rumination among boys. Higher positive affectivity in boys and girls and higher trust in boys predicted decreases in co-rumination across a 3-year interval. Fifth, although depression involves both increased negative affect and decreased positive affect, researchers studying best friend dyads so far solely associated depression with communication about problems. The sixth paper focused on different ways in which best friends talk about happy events and associated positive feelings. Concurrently, co-dampening was found to be maladaptive by predicting higher depressive symptoms and lower friendship quality. Co-enhancing appeared adaptive, showing concurrent associations with lower depressive symptoms and higher friendship quality. Over a 1-year interval, depressive symptoms predicted relative increases in co-dampening. In the final chapter, avenues for future research are discussed, together with clinical implications.

In sum, the findings of the current dissertation further clarified how, when, and for whom co-rumination is related to depressive symptoms. In addition, preliminary evidence was obtained for the relevance of studying communication about uplifting events. Insights provided by the present dissertation may lead to more efficient use of prevention and intervention efforts.