Date of Graduation

2015

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Psychology

Committee Chair

Amy Fiske

Committee Co-Chair

Karen G Anderson

Committee Member

Barry A Edelstein

Committee Member

Dina L Jones

Committee Member

Daniel W McNeil

Abstract

The current study examined potential mediators of the association between physical disability and depressive symptoms, along with positive mental health variables, including meaning in life and positive affect, within the framework of an empirically supported model of depression---the behavioral model of depression (Lewinsohn, 1985). The behavioral model of depression posits that reduced contact with positive reinforcement in the environment (i.e., engagement in pleasant events) precipitates and maintains depressive symptoms (Lewinsohn et al., 1985). Treatment studies have demonstrated the efficacy of interventions based on the behavioral model of depression in older adults (Cuijpers et al., 2007; Dimidjian et al., 2006; Hopko et al., 2003). The application of the behavioral model of depression to understanding the link between physical disability and depressive symptoms fits well with previous conceptualizations specifying the ways in which disability may affect mood (Bruce, 2001). First, consistent with role of life events in the behavioral model of depression (Lewinsohn et al., 1985), onset of disability can function as a discrete life event with the potential to create initial dysregulation in mood and disruption in schedules of reinforcement (Bruce, 2001; Dunne et al., 2011; Heckhausen et al., 2010), conditions that serve as catalysts for reduction in positive reinforcement over time (Lewinsohn, 1985). Second, physical disability is often chronic in nature and requires goal-adjustment and various forms of coping for successful adaption over time (Boerner, 2004; Hall et al., 2010). Failure to successfully adjust goals and coping strategies in response to physical disability may lead to reduced positive reinforcement if older adults do not replace lost activities with new ones, thereby increasing risk for depression over time (Duke et al., 2002). The current study was designed to examine whether the frequency of pleasant events, as well as frequency by pleasantness of events product (i.e., frequency of pleasant events and frequency x pleasantness of events), mediated the association between physical disability and affective outcomes (depressive symptoms, positive affect, meaning in life), after controlling potential confounds (age, gender, education, cognitive functioning, and perceived social support; Blazer, 2003). Participants were (N = 82) adults 65 years and older recruited from Morgantown, WV and surrounding towns/cities, Mage = 77.6 (SD = 8.0), 64.6% female, 97.6% White. Questionnaires measured physical disability (ADLS/IADLS), affective outcomes (GDS, GSIS-MIL, PANAS-PA), pleasant events (OPPES), and covariates (MoCA, DSSI, demographics). Simple mediation analyses with each proposed mediator (frequency of pleasant events and frequency x pleasantness of events) predicting affective outcomes were conducted using Preacher and Hayes' (2008) bootstrapping macro in SPSS. Consistent with predictions, frequency of pleasant events mediated the association between physical disability and affective outcomes, including depressive symptoms (unstandardized coefficient = 0.16, 95% bias-corrected CI [0.03, 0.41]), meaning in life (unstandardized coefficient = -1.58, 95% bias-corrected CI [-3.19, -0.47]), and positive affect (unstandardized coefficient = -2.65, 95% bias-corrected CI -5.38, -0.88]). The frequency by pleasantness of events product mediated the association between physical disability and affective outcomes (depressive symptoms: unstandardized coefficient = 0.11, 95% bias-corrected CI [0.01, 0.35]; meaning in life: unstandardized coefficient = -1.10, 95% bias-corrected CI [-2.59, -0.13]; positive affect: unstandardized coefficient = -1.89, 95% bias-corrected CI -4.38, -0.26). Mediation effects remained after controlling for covariates. Post hoc analyses revealed that after controlling for frequency of pleasant events, there was no longer significant indirect effect of pleasantness ratings, suggesting that frequency of pleasant events is most impactful in accounting for the association between physical disability and affective outcomes. Results are consistent with the behavioral mode of depression and generate ideas for future research, including prospective study designs, inclusion of daily diaries to capture real-time activity and mood, and inclusion of variables that may account for additional variance in the association between physical disability and affective outcomes in multiple mediation models, such the role of avoidance. Major depressive disorder (MDD) is a mental health condition characterized by the presence of depressed mood and/or anhedonia most of the day, nearly every day for two weeks, along with a minimum of five of nine additional symptoms (e.g., loss of energy, feelings of worthlessness or guilt; American Psychiatric Association, 2013). By the year 2020, MDD is expected to be the second leading cause of disease burden worldwide surpassing the disease burden attributed to road-traffic accidents and cardiovascular disease (Murray & Lopez, 1997). MDD is associated with increased all-cause and disease-related mortality (Kohler et al., 2013; Meijer et al., 2011; Park, Katon, & Wolf, 2013; Pinquart & Duberstein, 2010; Zheng et al., 1997). In addition, MDD is one of the strongest predictors of suicide across the life span (Brown, Beck, Steer, & Grisham, 2000; Conwell, Duberstein, & Caine, 2002). The economic consequences of MDD in the U.S. are staggering. In 2000, the cost of MDD, including direct treatment costs, morbidity, and mortality, was {dollar}81.1 billion (Greenberg et al., 2000). Reducing prevalence rates of MDD through interventions is a public health imperative that first begins with identifying the groups that are vulnerable to depressive symptoms.

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