Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Psychology

Supervisor

Schermer, Julie Aitken

2nd Supervisor

Saklofske, Donald H.

Co-Supervisor

Abstract

Rumination is a past-focused distress response characterized by repetitive and passive fixation on symptoms, possible causes, and/or consequences of distress (Nolen-Hoeksema, 1991). To date, previous measures of rumination have focused on general levels of rumination without considering the content of ruminative thought. This dissertation describes the development of a new rumination measure, the Rumination Domains Questionnaire (RDQ), which considers the content of ruminative thought. Furthermore, the present dissertation describes group differences found in the content of ruminative thought that have been difficult and/or unfeasible to capture in research prior to the introduction of the RDQ. In the introduction, a case is made for how scientists and practitioners may benefit from such a scale and how such a scale should be developed based on the scale development literature. Study 1 describes the rigorous procedures which constituted scale development, including item generation and selection based on empirical criteria. Study 2 is concerned with the validation of the RDQ in terms of reliability, concurrent validity, convergent validity, discriminant validity, and structural validity using two samples: a student sample and a community sample. In this study, reliability, concurrent, convergent, and to a lesser extent discriminant validity is supported, as was the scale’s structural validity as a 10-factor scale (domains as factors). In Study 3, the criterion and incremental validity of the scale was tested using daily diary methods. In this study, daily rumination (specific to a domain) was predicted by the corresponding RDQ domain score, whereas the RDQ-total score predicted relevant outcomes such as negative mood and amotivation, often even above and beyond the effect of other rumination scales. In Study 4, criterion validity was assessed once again, reliability was demonstrated (both internal consistency and test-retest reliability), and relationships with social desirability were examined. Moreover, two samples were collected: a student sample and an older sample, with which sex differences and differences between the samples in rumination content, as well as anxiety and depression, were investigated. Overall, these studies provide promising preliminary evidence for the RDQ’s validity, which may be used to assess the previously oft-neglected area of rumination content.

Summary for Lay Audience

Rumination is a past-focused distress response characterized by repetitive and passive fixation on symptoms, possible causes, and/or consequences of distress. Overall, researchers have generally been interested in the extent to which individuals ruminate but have largely neglected the content of the rumination – that is, what people ruminate about. The dearth of research on this topic is at least partially due to a lack of measurement tools that capture the degree to which individuals ruminate about certain issues. The purpose of this dissertation was to create a rumination scale that considers the content of rumination. Based on the previous literature, as well as clinical and counselling case studies, I generated approximately 250 statements for 10 domains of life. After expert screening, these statements were subjected to rigorous statistical treatments to reduce the initial pool of items to a total of 60 statements (six statements per domain). In a subsequent study, a student sample and a community sample completed the 60 items, as well as various other measures to assess the extent to which this new scale (called the Rumination Domains Questionnaire; RDQ) complies with other constructs in such a way that is consistent with other rumination measures, previous rumination research, as well as relevant theory. Overall, the RDQ did well according to these empirical and theoretical criteria. In the next study, participants completed the RDQ and then every day for seven days reported the time they spent ruminating about each domain of life, as well as their daily sleep quality, amotivation, and negative mood. It was found that the RDQ domains successfully predicted the daily rumination in the corresponding domain, as well as outcomes such as amotivation and negative mood, supporting the validity of the RDQ (i.e., that the RDQ measures what it is supposed to measure). In the final study, it was demonstrated that the RDQ is reliable, and correlates with relevant outcomes. Further, it was found that women ruminate more than men in most domains of life and that students ruminated more than older individuals in almost all domains of life.

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