Previous research has shown that ruminative thoughts are associated with impairments in well-being. However, the direction of this relationship is unclear. There are findings indicating both unidirectional and bidirectional (i.e., reciprocal) relationships. The question therefore arises how rumination and well-being are related. Furthermore, previous findings on the relationship between rumination and problem solving are heterogeneous. However, since ruminative thinking involves an increased use of resources to solve a problem, it is assumed that these resources (i.e., attention and effort) can positively (...) mediate the relationship between rumination and problem solving. On the other hand, it is also assumed that the negative effects of rumination on well-being negatively mediate the relation between rumination and problem solving. In Study 1 and 2 of the present dissertation, therefore, the relationship between rumination, well-being, resources (i.e., attention and effort), and problem solving was examined in a longitudinal way. The assumption that rumination also has a functional side is further supported by the hypothesis that ruminative thoughts can also lead to more constructive and deliberative thoughts about a problem, which in turn can foster the positive reappraisal of an event and ultimately personal growth. Study 3 of the present dissertation therefore examined to what extent ruminative thoughts can also lead to more constructive coping strategies. Furthermore, it was analysed to what extent the appraisal of an event as threatening and uncontrollable can cause the occurrence of ruminative thoughts. In summary, this work focuses on the functional and dysfunctional aspects of ruminative thoughts related to human well-being and problem solving. (shrink)