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%).
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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
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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.
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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
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What explains the association between socioeconomic status and depression among Vietnamese
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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
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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
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What explains the association between socioeconomic status and depression among Vietnamese
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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
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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
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What explains the association between socioeconomic status and depression among Vietnamese
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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
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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
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What explains the association between socioeconomic status and depression among Vietnamese
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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
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What explains the association between socioeconomic status and depression among Vietnamese
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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
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What explains the association between socioeconomic status and depression among Vietnamese
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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
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What explains the association between socioeconomic status and depression among Vietnamese
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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
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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
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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.
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