Longitudinal Processes That Predict Affective Symptoms

Abstract

Depressive and anxiety symptoms can be associated with high levels of impairment and distress. Thus, it is important to understand the processes that contribute to the exacerbation and alleviation of affective symptoms. Various factors have been implicated, including individuals’ tendencies towards rumination and mindfulness, and the psychological processes of stress and sleep disturbance. While these associations are generally well established, the bulk of existing research is dominated by specific conceptualisations, and thus limited measurement, of these constructs, and there is a paucity of research into theoretically important interactive processes. Hence, the aim of this thesis was to explore various key mechanisms by which core depression and anxiety symptoms can change over time, including the direct and/or interactive effects of dispositional rumination and mindfulness (Study 1), and the effects of psychological stress, whether direct, mediated by rumination and/or sleep disturbance, and/or attenuated by dispositional mindfulness (Study 2). A prospective study was conducted, whereby a convenience sample of Australian community adults completed three online surveys, three months apart (Time 1, n = 730; Time 2, n = 498; and Time 3, n = 353). Participants answered questions about their recent experiences of depression, anxiety, stress, and sleep disturbance, and their tendencies towards non-mood-responsive rumination, mindful-acting-with-awareness, and mindful-non-judging. Findings from Study 1 revealed that greater rumination directly predicted increased depression across three months, and stress across three and six months. In addition, greater mindful-acting-with-awareness directly predicted decreased anxiety across three months. Finally, high mindful-acting-with-awareness attenuated the effects of lower non-judging on increasing anxiety and stress across three months, in addition to the effects of greater rumination on increasing anxiety and depression across six months. Findings from Study 2 revealed that greater stress predicted increased six-month depression and anxiety indirectly via three-month sleep disturbance, and also via rumination leading to three-month sleep disturbance, whereas rumination uniquely mediated between stress and six-month depression. Further, high mindful-acting-with-awareness attenuated the effects of greater stress on increased anxiety across six months. Overall, the findings suggested that: (1) a general tendency to ruminate is more predictive of later stress and depression over anxiety symptoms; (2) that poor sleep plays a key intermediary role in linking subjective stress to later affective symptoms (as a unique factor and also following rumination); and (3) a tendency to attend to present-moment experiences is especially protective in attenuating the effects of self-critical appraisal processes and/or subjective stress on later anxiety. Various theoretical, clinical, and methodological considerations are implicated from the research findings, elucidating numerous avenues for continued research. Of particular clinical importance, the findings align with mechanistic accounts of mindfulness-based treatment interventions by suggesting that regularly attending to present-moment experiences may protect against escalating distress by buffering the effects of harmful self-evaluative processes.