What explains the association between socioeconomic status and depression among vietnamese adults

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WHAT EXPLAINS THE ASSOCIATION BETWEEN SOCIOECONOMIC STATUS AND DEPRESSION AMONG VIETNAMESE ADULTS? Vuong Diem Khanh Doan Doctor of Medicine (Hue University of Medicine and Pharmacy) Master in Public Health Methodology (Universite Libre de Bruxelles) Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy School of Public Health and Institute of Health and Biomedical Innovation Queensland University of Technology April, 2011 Keywords Chronic stress, cross-sectional survey, depression, life time trauma, mastery, mediating effect, prevalence, psychological resources, recent life events, self esteem, social support, socioeconomic status, Vietnamese adults. i What explains the association between socioeconomic status and depression among Vietnamese adults? Abstract Background Depression is a major public health problem worldwide and is currently ranked second to heart disease for years lost due to disability. For many decades, international research has found that depressive symptoms occur more frequently among low socioeconomic (SES) individuals than their more-advantaged peers. However, the reasons as to why those of low socioeconomic groups suffer more depressive symptoms are not well understood. Studies investigating the prevalence of depression and its association with SES emanate largely from developed countries, with little research among developing countries. In particular, there is a serious dearth of research on depression and no investigation of its association with SES in Vietnam. The aims of the research presented in this Thesis are to: estimate the prevalence of depressive symptoms among Vietnamese adults, examine the nature and extent of the association between SES and depression and to elucidate causal pathways linking SES to depressive symptoms Methods The research was conducted between September 2008 and November 2009 in Hue city in central Vietnam and used a combination of qualitative (in-depth interviews) and quantitative (survey) data collection methods. The qualitative study contributed to the development of the theoretical model and to the refinement of culturally-appropriate data collection instruments for the quantitative study. The main survey comprised a cross-sectional population–based survey with randomised cluster sampling. A sample of 1976 respondents aged between 25-55 years from ten randomly-selected residential zones (quarters) of Hue city completed the questionnaire (response rate 95.5%). ii What explains the association between socioeconomic status and depression among Vietnamese adults? Measures SES was classified using three indicators: education, occupation and income. The Center for Epidemiologic Studies-Depression (CES-D) scale was used to measure depressive symptoms (range0-51, mean=11.0, SD=8.5). Three cut-off points for the CES-D scores were applied: ‘at risk for clinical depression’ (16 or above), ‘depressive symptoms’ (above 21) and ‘depression’ (above 25). Six psychosocial indicators: life time trauma, chronic stress, recent life events, social support, self esteem, and mastery were hypothesized to mediate the association between SES and depressive symptoms. Analyses The prevalence of depressive symptoms were analysed using bivariate analyses. The multivariable analytic phase comprised of ordinary least squares regression, in accordance with Baron and Kenny’s three-step framework for mediation modeling. All analyses were adjusted for a range of confounders, including age, marital status, smoking, drinking and chronic diseases and the mediation models were stratified by gender. Results Among these Vietnamese adults, 24.3% were at or above the cut-off for being ‘at risk for clinical depression’, 11.9% were classified as having depressive symptoms and 6.8% were categorised as having depression. SES was inversely related to depressive symptoms: the least educated those with low occupational status or with the lowest incomes reported more depressive symptoms. Socioeconomicallydisadvantaged individuals were more likely to report experiencing stress (life time trauma, chronic stress or recent life events), perceived less social support and reported fewer personal resources (self esteem and mastery) than their moreadvantaged counterparts. These psychosocial resources were all significantly associated with depressive symptoms independent of SES. Each psychosocial factor showed a significant mediating effect on the association between SES and depressive iii What explains the association between socioeconomic status and depression among Vietnamese adults? symptoms. This was found for all measures of SES, and for males and females. In particular, personal resources (mastery, self esteem) and chronic stress accounted for a substantial proportion of the variation in depressive symptoms between socioeconomic groups. Social support and recent life events contributed modestly to socioeconomic differences in depressive symptoms, whereas lifetime trauma contributed the least to these inequalities. Conclusion This is the first known study in Vietnam or any developing country to systematically examine the extent to which psychosocial factors mediate the relationship between SES and depression. The study contributes new evidence regarding the burden of depression in Vietnam. The findings have practical relevance for advocacy, for mental health promotion and health-care services, and point to the need for programs that focus on building a sense of personal mastery and self esteem. More broadly, the work presented in this Thesis contributes to the international scientific literature on the social determinants of depression. iv What explains the association between socioeconomic status and depression among Vietnamese adults? Table of Contents Keywords….. ................................................................................................................ i Abstract…… ................................................................................................................ ii Table of Contents ......................................................................................................... v List of Figures ............................................................................................................. ix List of Tables ............................................................................................................... x List of Abbreviations ................................................................................................ xiv Statement of Original Authorship ............................................................................ xvii Contributions to Thesis ........................................................................................... xviii Ethical Clearance ...................................................................................................... xix Acknowledgments ...................................................................................................... xx CHAPTER 1:INTRODUCTION .............................................................................. 1 1.0 Background ......................................................................................................... 1 1.1 Research aim and questions ............................................................................... 5 1.1.1 Research aim ............................................................................................. 5 1.1.2 Research questions .................................................................................... 5 1.2 Outline of this Thesis .......................................................................................... 5 CHAPTER 2:LITERATURE REVIEW.................................................................. 7 2.0 Introduction ........................................................................................................ 7 2.1 Definition of depression ..................................................................................... 7 2.2 Psycho-behavioural theories of depression ........................................................ 8 2.2.1 Learned helplessness ................................................................................. 9 2.2.2 Cognitive constructions of self and reality................................................ 9 2.2.3 Response Contingent Positive Reinforcement Theory ........................... 10 2.2.4 Psychoanalytic theories ........................................................................... 10 2.3 Rating scales for measuring depression............................................................ 11 2.3.1 Classification ........................................................................................... 11 2.3.2 Overview of currently-used depression rating scales.............................. 14 2.4 International prevalence of depression ............................................................. 19 2.5 The relationship between socioeconomic status and depression ...................... 24 2.5.1 Introduction ............................................................................................. 24 2.5.2 Conceptualising SES ............................................................................... 24 2.5.3 Education and depression........................................................................ 26 2.5.4 Occupation and depression ..................................................................... 27 v What explains the association between socioeconomic status and depression among Vietnamese adults? 2.5.5 Income and depression ............................................................................ 27 2.6 Conceptualising the association between SES, depression and health ............. 30 2.7 The association between stress and depression ................................................ 33 2.7.1 Conceptualising stress ............................................................................. 33 2.7.2 The association between stress and depression ....................................... 34 2.8 The association between social support and depression ................................... 36 2.8.1 ConceptualiSing social support .............................................................. 36 2.8.2 The association between Social support and depression ......................... 38 2.9 The association between psychological resources and depression ................... 40 2.9.1 Conceptualising self esteem .................................................................... 40 2.9.2 The association between self esteem and depression .............................. 41 2.9.3 Conceptualising mastery ......................................................................... 42 2.9.4 The association between mastery and depression ................................... 44 2.10 The association between SES and stress, social support and psychological resources……………….. ........................................................................................... 45 2.10.1 Association between SES and stress ..................................................... 45 2.10.2 Association between SES and social support ....................................... 47 2.10.3 Association between SES and psychological resources ....................... 49 2.11 Research on depression in Vietnam .................................................................. 53 2.12 Hypotheses and conceptual model of the study ................................................ 55 2.11.1 Hypotheses ............................................................................................ 55 2.11.2 Conceptual model ................................................................................. 56 2.13 Chapter summary .............................................................................................. 57 CHAPTER 3:RESEARCH METHODS ................................................................ 59 3.0 Introduction....................................................................................................... 59 3.1 Timeline ............................................................................................................ 59 3.2 Geographic location and scope ......................................................................... 59 3.3 Research design……………………………………………………………….61 3.4 Phase 1: Pilot study........................................................................................... 62 3. 4.1 Exploratory qualitative research.............................................................. 62 3. 4.2 Pilot study of the quantitative survey ...................................................... 67 3.5 Phase 2: Main survey ........................................................................................ 75 3.5.1 Sample size .............................................................................................. 75 3.5.2 Sample selection ...................................................................................... 76 3.5.3 Training of data collectors....................................................................... 77 3.5.4 Preparing for data collection ................................................................... 77 3.5.5 Data collection......................................................................................... 77 3.5.6 Data management .................................................................................... 78 3.5.7 Data screening ......................................................................................... 79 3.5.8 Measures .................................................................................................. 80 3.5.9 Data analyses ......................................................................................... 105 3.6 Summary ......................................................................................................... 113 vi What explains the association between socioeconomic status and depression among Vietnamese adults? CHAPTER 4:RESULTS........................................................................................ 115 4.0 Introduction .................................................................................................... 115 4.1 Prevalence of depressive symptoms and depression ...................................... 116 4.1.1 Overall prevalence of depression .......................................................... 116 4.1.2 Sociodemographic factors and the prevalence of depression ............... 116 4.2 Descriptive (bivariate) analyses of the association between SES, depression and each of the mediators......................................................................................... 122 4.2.1 Socioeconomic status and depression scores (CES-D) ......................... 122 4.2.2 Socioeconomic status and lifetime trauma ............................................ 123 4.2.3 Socioeconomic status and chronic stress .............................................. 124 4.2.4 Socioeconomic status and recent life events ......................................... 125 4.2.5 Socioeconomic status and social support .............................................. 126 4.2.6 Socioeconomic status and self esteem .................................................. 127 4.2.7 Socioeconomic status and mastery........................................................ 128 4.3 Mediation analyses: The causal steps approach - three steps in Baron and Kenny’s framework.................................................................................................. 129 4.3.1 Step 1: The Total effects of SES on depression .................................... 129 4.3.2 Step 2: Multiple regression of potential mediators on SES .................. 133 4.3.3 Step 3: Multiple regression of CES-D score on potential mediators - controlling for the effect of SES ......................................................... 146 4.4 Estimating the size and significance of the indirect or mediated effects........ 150 4.4.1 The mediated effect of lifetime trauma on SES and depression ........... 151 4.4.2 The mediated effect of chronic stress on SES and depression .............. 155 4.4.3 The mediation effect of recent life events on SES and depression ....... 158 4.4.4 The mediation effects of social support on SES and depression .......... 162 4.4.5 The indirect effects or mediated effect of self esteem on SES and depression .............................................................................................. 166 4.4.6 The indirect effect or mediated effect of mastery on SES and depression .............................................................................................. 169 4.5 Percentage mediation of total effects of SES on CES-D: summary ............... 172 4.6 Summary......................................................................................................... 184 CHAPTER 5:DISCUSSION ................................................................................. 187 5.0 Introduction ....................................................................................................... 187 5.1 Prevalence of depressive symptoms and depression ...................................... 187 5.1.1 Prevalence of being ‘at risk for clinical depression’ ............................. 188 (CES-D≥ 16) ................................................................................................... 188 5.1.2 Prevalence of depressive symptoms (CES-D > 21) and depression (CES-D > 25) ........................................................................................ 190 5.1.3 Gender and depression………………………………………………..192 5.1.4 Age and depression …………………………………………………..193 5.1.5 SES and the prevalence of depression………………………………..195 5.2 Psychosocial mediators of the SES-depression relationship .......................... 197 vii What explains the association between socioeconomic status and depression among Vietnamese adults? 5.2.1 5.2.2 5.2.3 5.2.4 5.2.5 5.2.6 5.2.7 Association between SES and levels of depressive symptoms ............. 197 The mediating role of stress .................................................................. 198 The mediating role of social support ..................................................... 203 The mediating role of self esteem ......................................................... 206 The mediating role of mastery............................................................... 208 Comparing mediating effects of different psychosocial factors ............ 213 Gender difference in mediating effects ................................................. 219 5.3 Study strengths, limitations and implications for further research ................. 219 5.3.1 Strengths ................................................................................................ 219 5.3.2 Study limitations and implications for further research ........................ 221 5.4 Implications for mental health policy in Vietnam .......................................... 224 5.5 Conclusion ...................................................................................................... 232 BIBLIOGRAPHY .................................................................................................. 234 APPENDIX A: GUIDELINES FOR EXPLORATORY QUALITATIVE RESEARCH ……………………………………………………………………….267 APPENDIX B: SURVEY QUESTIONNAIRE ...................................................... 271 APPENDIX C: RESULTS OF EXPLORATORY QUALITATIVE RESEARCH 293 APPENDIX D: RESULTS OF PILOT QUANTITATIVE RESEARCH .............. 303 APPENDIX E: CONFIRMATORY FACTOR ANALYSIS.................................. 324 APPENDIX F: BIVARIATE RELATIONSHIPS BETWEEN EACH SES INDICATOR AND THE CONTROL VARIABLES (AGE, MARITAL STATUS, SMOKING, DRINKING AND CHRONIC DISEASES) ........................................ 327 APPENDIX G: VIETNAM MAP AND LOCATION OF STUDY SITE.............. 333 APPENDIX H: PICTURES OF HOUSEHOLD BOOKLET AND TRANING DATA COLLECTORS ............................................................................................ 335 viii What explains the association between socioeconomic status and depression among Vietnamese adults? List of Figures Figure 2.1. Classification of rating scales for depression …………………………..12 Figure 2.2. Theoretical model of the association between socioeconomic status, depression and health outcomes ......................................................................... 32 Figure 2.3. Conceptual model of the association between SES and depression ........ 56 Figure 3.1. Research design of the study ................................................................... 61 Figure 3.2. Histograms of lifetime trauma scale by sex............................................. 86 Figure 3.3. Histograms of chronic stress scale by sex ............................................... 89 Figure 3.4. Histograms of the recent life events scale by sex .................................... 92 Figure 3.5. Histograms of the social support scale by sex ......................................... 94 Figure 3.6. Histogramsof self esteem scale by sex .................................................... 96 Figure 3.7. Histograms of the mastery scale by sex…………………………….….98 Figure 3.8. Histograms of CES-D scale by sex........................................................ 104 Figure 3.9. Mediational model using Baron and Kenny’s (1986) notation ............. 107 Figure 4.1. Prevalence of depressive symptoms (CES-D > 21) by education (%) . 119 Figure 4.2. Prevalence of depressive symptoms (CES-D > 21) by occupation (%) 120 Figure 4.3. Prevalence of depressive symptoms ( CES-D > 21) by income (%) .... 121 ix What explains the association between socioeconomic status and depression among Vietnamese adults? List of Tables Table 2.1 Diagnostic schedules assessing depression within currently-used diagnosis systems………………………………………………………………16 Table 2.2 Dimensional rating scales: clinician- or observer-rated scales for depression……………………………………………………………………... 17 Table 2.3 Self-rated scales for depression………………………………………... 18 Table 3.1 Pilot study: internal consistency of scales………………………………. 71 Table 3.2. Pilot study: Summary of the fit statistics of mastery scale……………… 72 Table 3.3 Ordinary Least Squares Regression of CESD score on income (controlled for age), comparing the two models: values of missing income included (substituted) and excluded…………………………………………………….. 80 Table 3.4 SES distribution of the sample………………… 82 Table 3.5 Frequency of lifetime trauma items…………………………………….. 84 Table 3.6 Descriptive statistics of the lifetime trauma scale……………………... 85 Table 3.7 Frequency of chronic stress items……………………………………… 87 Table 3.8 Descriptive statistics of chronic stress scale……………………………. 88 Table 3.9 Frequency of recent life event items…………………………………….90 Table 3.10 Descriptive statistics of the recent life event scale……………………. 91 Table 3.11 Descriptive statistics of the social support scale………………………. 93 Table 3.12 Descriptive statistics of the self esteem scale…………………………. 95 Table 3.13 Descriptive statistics of the mastery scale…………………………….. 97 Table 3.14 Mean age (SD) and age group distribution of the sample……………. 99 Table 3.15 Marital status distribution of the sample…………………………….. 100 Table 3.16 Smoking status distribution of the sample…………………………... 100 Table 3.17 Alcohol consumption distribution of the sample…………………….. 101 x What explains the association between socioeconomic status and depression among Vietnamese adults? Table 3.18 Chronic diseases distribution of the sample………………………….. 102 Table 3.19 Descriptive statistics of the CES-D scale……………………………. 103 Table 3.20 Simple Linear Regression of CES-D score on SES indicators………. 106 Table 3.21 Bivariate inter-correlation matrix of mediator variables…………….. 110 Table 3.22 Ordinary least squares regression of CES-D score on education without and with adjusted for clusters in quarter and in interviewer in females (all models adjusted for age)…………………………………………………….. 113 Table 4.1 Percentage of ‘category at risk for clinical depression’, percentage with depressive symptoms and percentage with depression by demographic characteristics and SES………………………………………………………. 117 Table 4.2 CES-D scale: mean scores (and 95% CI) by SES for males and females……………………………………………………………………….. 123 Table 4.3 Lifetime trauma scale: mean scores (and 95% CI) by SES for males and females……………………………………………………………………….. 124 Table 4.4 Chronic stress scale: mean scores (and 95% CI) by SES for male and female…………………………………………………………………………125 Table 4.5 Recent life events scale: mean scores (and 95% CI) by SES for males and females……………………………………………………………………….. 126 Table 4.6 Social support scale: mean scores (and 95% CI) by SES for males and females……………………………………………………………………….. 127 Table 4.7 Self esteem scale: mean scores (and 95% CI) by SES for males and females……………………………………………………………………….. 128 Table 4.8 Mastery scale: mean scores (and 95% CI) by SES for males and females……………………………………………………………………….. 129 Table 4.9 Ordinary least squares regression of CES-D score on SES…………….. 130 Table 4.10 Ordinary Least Squares Regression of Lifetime trauma score on SES. 133 Table 4.11 Ordinary least squares regression of chronic stress score on SES…….135 Table 4.12 Ordinary least squares regression of recent life events score on SES... 138 Table 4.13 Ordinary least squares regression of social support score on SES……. 140 xi What explains the association between socioeconomic status and depression among Vietnamese adults? Table 4.14 Ordinary least squares regression of self esteem score on SES………142 Table 4.15 Ordinary least squares regression of mastery score on SES…………. 144 Table 4.16 Ordinary Least Squares Regression of CES-D on possible mediators (psychosocial resources) when controlling for the effect of education……… 146 Table 4.17 Ordinary least squares regression of CES-D on possible mediators (psychosocial resources) when controlling for occupation………………….. 148 Table 4.18 Ordinary least squares regression of CES-D on possible mediators (psychosocial resources) when controlling income………………………….. 149 Table 4.19a Ordinary least squares regression of CES-D on SES indicators and the mediated effect of lifetime trauma for males………………………………… 153 Table 4.19b Ordinary least squares regression of CES-D on SES indicators and the mediated effect of lifetime trauma for females……………………………….154 Table 4.20a Ordinary least squares regression of CES-D on SES indicators and the mediation effects of chronic stress among males……………………………. 156 Table 4.20b Ordinary least squares regression of CES-D on SES indicators and the mediation effect of chronic stress among females…………………………... 157 Table 4.21a Ordinary least squares regression of CES-D on SES indicators and the mediated effects of recent life events among males…………………………. 160 Table 4.21b Ordinary least squares regression of CES-D on SES indicators and the mediated effect of recent life events among females…………………………161 Table 4.22a Ordinary least squares regression of CES-D on SES indicators and the mediation role of social support among males………………………………. 164 Table 4.22b Ordinary least squares regression of CES-D on SES indicators and the mediation effects of social support among females………………………….. 165 Table 4.23a Ordinary least squares regression of CES-D on SES indicators and the mediation of self esteem among males………………………………………. 167 Table 4.23b Ordinary least squares regression of CES-D on SES indicators and the mediation role of self esteem among females………………………………...168 Table 4.24a Ordinary least squares regression of CES-D on SES indicators and the mediation effect of mastery among males…………………………………… 170 Table 4.24b Ordinary least squares regression of CES-D on SES indicators and the mediation effect of mastery among females…………………………………. 171 xii What explains the association between socioeconomic status and depression among Vietnamese adults? Table 4.25 Summary of the percentages of total effects (education on CES-D) mediated by psychosocial resources…………………………………………. 173 Table 4.26 Summary table: percentages of total effects (occupation on CES-D) mediated by psychosocial resources…………………………………………. 176 Table 4.27 Summary table: percentages of total effects (income on CESD) mediated by psychosocial resources…………………………………………………….179 Table 4.28 Average percentages of total effects (SES on CES-D) mediated by hypothesised mediators………………………………………………………. 182 xiii What explains the association between socioeconomic status and depression among Vietnamese adults? List of Abbreviations ACE Adverse childhood experiences BDI Beck Depression Inventory BRAC Bangladesh Rural Advancement Committee CDS Carroll Rating Scale for Depression CES-D Center for Epidemiologic Studies-Depression Scale CFA Confirmatory factor analysis CFI Comparative fit index CHD Coronary Heart Disease CI Confidence interval CIDI Composite International Diagnostic Interview CIS-R Clinical Interview Schedule- Revised DACL Depression Adjective Check Lists D-ARK Depression-Arkansas Scale DASS Depression Anxiety Stress Scale DIGS Diagnostic Interview for Genetic Studies DIS Diagnostic Interview Schedule DSM-III-R Diagnostic and Statistical Manual of Mental Disorders, Third Edition, revised DSM-IV-TR Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, text revision EFA Exploratory factor analysis FA Factor analysis xiv What explains the association between socioeconomic status and depression among Vietnamese adults? GFI Goodness of Fit Index GMSE Geriatric Mental State Examination Ham-D Hamilton Rating Scale for Depression HPA Hypothalamic–pituitary–adrenocortical axis ICC Intra-class correlation coefficient ICD-10 International Classification of Diseases–10th revision ICPE International Consortium of Psychiatric Epidemiology IDD Inventory to Diagnose Depression IDS-C Inventory of Depressive Symptomatology- Clinician Administered IDS-SR Inventory of Depressive Symptomatology- Self Reported KECAS Korean Epidemiologic Catchment Area Study MADRS Mongomety-Asberg Depression Rating Scale MDD Major depressive disorder MINI Mini-international Neuropsychiatric Interview MSPSS Multidimensional Scale of Perceived Social Support NCS US National Co-morbidity Study NFI Normed Fit Index NS Not significant OLS Ordinary least squares OR Odds ratio PCA Principal component analysis PHQ-2 Patient Health Questionnaire Two-item Screener PIC Positive influences in childhood PRIME-MD Primary Care Evaluation of Mental Disorders xv What explains the association between socioeconomic status and depression among Vietnamese adults? RMSEA Root Mean Square Error of Approximation RSES The Rosenberg Self-Esteem Scale SADS Schedule for Affective Disorders and Schizophrenia SCID-I Structures Clinical Interview for DSM-IV Axis I Disorders SDDS-PC Symptom-Driven Diagnostic System for Primary Care SCAN Schedule for Clinical Assessment in Neuropsychiatry SEM Structural Equation Modelling SES Socioeconomic status SAM Sympathetic adrenal–medullary system SD Standard deviation SWAN Study of Women’s Health Across the Nation VBSP Vietnam Bank for Social Policies VO Village Organisation WHO World Health Organization Zung SDC Zung Self-Rating Depression Scale xvi What explains the association between socioeconomic status and depression among Vietnamese adults? Contributions to Thesis The work presented in this thesis was conducted by the author under the supervision of Professor Gavin Turrell (Principal Supervisor) and Professor Michael Dunne (Associate Supervisor) at the School of Public Heath, Queensland University of Technology, Australia, and A. Professor Vo Van Thang (Associate Supervisor), at Hue College of Medicine and Pharmacy, Vietnam. The work conducted by the author included: Conceptualisation of research program, design and methodology; development of funding submissions; submission of ethics applications; measurement design and development; data collection, data management and analyses; interpretation of results and the preparation of this thesis. This PhD research program and the study presented in this thesis was conducted with funding support from Atlantic Philanthropies. xviii What explains the association between socioeconomic status and depression among Vietnamese adults?
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