The extended perseverative cognition hypothesis: Testing the effects of worry/rumination on physical and behavioural health outcomes

Perseverative cognition (PC) is the repeated psychological activation of stress-related cognitions (including worry and rumination). The Perseverative Cognition Hypothesis (PCH) posits that, in the same way as stress, PC damages health via its ensuing physiological activation and, in recent years, PC has been shown to influence health via an indirect, behavioural pathway, termed the Extended PCH (EPCH). However, this evidence seldom considers experimental methodologies testing interventions, pathways, or how robust this is across health outcomes. The principal aim of this thesis was therefore to examine methods to reduce PC, its relationship with health behaviours/physical health outcomes, and moderating/mediating variables that may exacerbate and/or attenuate this relationship.
Both general and work-related worry and rumination predicted significantly higher scores in burnout and somatization, as well as lower scores in sleep quality while several mediation effects were found for the indirect pathway from job strain, through PC, to several health outcomes (Chapter 2; Study 1). Meta-analysis of 36 studies testing (non-pharmacological) interventions produced medium effect sizes for worry and rumination, corresponding to small, but positive, effect sizes for health behaviours (and small-medium positive effect sizes for sleep) (Chapter 3; Study 2). In a randomised controlled trial, participants in an augmented worry postponement intervention produced significantly lower worry duration (by ~15 minutes, on average, per day), relative to an active-control arm and those in the augmented worry postponement condition reported significantly shorter worry duration and lower worry frequency, relative to the standard arm. Neither of the interventions had any effect on sleep (Chapter 4; Study 3). In another study, worry and rumination (at baseline) predicted significantly poorer sleep quality (at 7 days follow-up). Worry, but not rumination, and PBC interacted to predict significantly lower physical activity frequency and consistent with mediation, the indirect paths from both worry and rumination, through PBC, to sleep quality and total sleep time were significant (Chapter 5; Study 4).
The findings of this thesis provide some support for the EPCH and varying degrees of support for the PCH. PC poses a serious, indirect, risk for disease processes via modifying health behaviours and influencing some physical health outcomes. Further work is needed to elucidate how PC interacts with other components known to predict (or influence) disease processes and to uncover new interventions that can attenuate the now axiomatic relationship between PC and ill-health.