Is Pessimism a Mediator between Intolerance of Uncertainty and Depression/General Anxiety?
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Intolerance of uncertainty (IU) is considered a transdiagnostic factor for several disorders including depression and generalised anxiety disorder (GAD), although the mechanism through which it has its effect is unclear. This study sought to examine if pessimism mediates the relationship between IU and depression/GAD. A cross-sectional design was used to test the hypothesis that pessimism is a mediator for the effect of IU on depression/GAD symptoms while controlling for rumination and worry respectively. Participants (N = 441) were recruited from Utrecht University and filled out several batteries of questionnaires, which were coded and analysed. Mixed results were found. Pessimism partially mediated the relationship between IU and depression while controlling for rumination, 95% CI[0.11, 0.2]. In the GAD model no mediation was found when controlling for worry, 95% CI [-0.01, 0.01], however, a partial mediation was found when worry was not controlled for, 95% CI[0.03, 0.06]. IU continued to explain a significant amount of variance of both depression and GAD when controlling for rumination and worry respectively. These results raise the possibility that pessimism may trigger worry causing a double mediation, and/or there is construct overlap between pessimism/worry. The results also have implications for theoretical models of IU, depression, and GAD, as well as for the development and maintenance of pessimism. Results also show that IU has a relationship with depression and GAD that is unique of pessimism, worry, and rumination, which has yet to be explained. There were several limitations of this study which require replication both longitudinally and experimentally.