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Background
Gradients in physical ill-health by socio-economic status are well-recognised.
Physical morbidity such as coronary heart disease and chronic bronchitis
are more prevalent in lower socio-economic status groups. This may
also be the case for common mental disorders like anxiety and depression,
and many studies suggest that depressive symptoms are more prevalent
in lower rather than higher socio-economic status groups.
What are the
explanations for these socio-economic gradients in ill-health? For
physical ill-health, characteristics of the psycho-social work environment,
such as low control over work, and lack of personal social support,
have been invoked as potential explanations of the social gradient
in addition to conventional risk factors such as health-related
behaviours. It is possible that these factors have a similar impact
on the social gradient in common mental disorders, particularly
depression. Possible explanations for social gradients in depression
may be sought in early life factors, in contemporary exposure to
stressors (including lack of material resources and excessive demands),
lack of social support at work and at home, and in pre-existing
physical illness.
If these factors
are important in explaining the social gradient in depression, what
might be their mechanism of action? A likely mechanism is suggested
by the stress hypothesis, where stress is conceptualized as an imbalance
between demands and resources. An excess of demands and lack of
resources in lower socio-economic strata might result in an increased
risk of illness. Not only might there be more exposure to stressors,
like life events and material problems in lower socio-economic groups,
but they may also be perceived differently by social status. For
instance, control over work and demands at work may be interpreted
differently by those in lower and higher socio-economic groups and
by men and women. Effective coping with stressors requires that
stressors are perceived and dealt with in a way that minimises their
threat to health. Furthermore, it depends on having both environmental
and personal coping resources to deal with stressors. These include
social supports and coping skills which may also differ in distribution
by socio-economic status and thus contribute to differences in combating
stressors.
Aims and
Objectives
This project will examine:
- qualitative
differences in stressors and supports at home and at work by social
status and gender;
- the mechanisms
by which these stressors and supports may contribute to social
inequalities in depression. The relative contribution of each
of these factors to explaining the social gradient in depression
will be assessed using quantitative analysis and the possibility
of common causes for both depression and physical illness will
be examined.
Study Design
The study sample will be chosen from a prospective occupational
cohort study, the Whitehall II Study of middle-aged male and female
civil servants. There are two parts to this investigation: qualitative
and quantitative. First, in-depth interviews of 120 participants
stratified by employment grade (the measure of socio-economic status),
gender and depression score will be conducted to assess how stressors,
supports and coping vary by employment grade. All these interviews
will include a semi-structured section elaborating on earlier questionnaire
responses, while 60 will also include an unstructured in-depth interview.
The quantitative part comprises analyses of risk factors, including
work and social support, from the whole Whitehall II cohort to explain
the employment grade gradient in depression (measured by the Composite
International Diagnostic Interview) found in this study.
Policy Implications
The research will aid in understanding which risk factors and which
protective factors, both at home and at work, are relevant to social
inequalities in depression and how these may differ by gender. It
is anticipated that this will identify possible points for intervention
with preventative programmes to promote mental health.
Project Summary
Promoting mental health is an integral part of the UK's national
health strategies. The project focused on depression, one of the
most prevalent of the mental health disorders.
It drew on analyses
of the Whitehall II study of 10308 civil servants, a prospective
cohort study of London-based office staff working in 20 civil service
departments. These analyses were informed by 75 qualitative interviews,
which explored individuals' everyday lives in the contexts of home,
work and neighbourhood.
The Whitehall
II cohort was first studied in 1985-1988 (baseline survey), with
the most recent wave of data collection in 1997-99 (phase 5). Civil
Service employment grade provides a finely-graded measure of occupational
position and the project used this measure to examine grade differences
in depressive symptoms over time, the comparative importance of
everyday stressors and protective factors, and the home and work-based
factors contributing to them.
Key findings
- The grade
gradient in depressive symptoms had become more marked over the
10 years of the Whitehall II Study. For women, a gradient had
emerged; for men, the gradient, already evident at the baseline
survey, had widened. Adjustment for upward and outward mobility
did not alter the overall grade gradients in depression among
men and women at phase 5.
- Adverse changes
in the psycho-social work environment (reduced skill discretion,
increased job demands and reduced work support) between phase
1 and phase 3 were predictors of depressive symptoms at phase
5. Those who were upwardly mobile were less likely to have depressive
symptoms. Further analyses suggested that improved work environment
is part of the explanation for the reduced depression scores among
those who were upwardly mobile. It is also suggested that those
who were in adverse work environments on more than one occasion
were at increased risk of depression. Adverse changes in perceived
material problems were also a predictor of depressive symptoms.
- Work characteristics
and material deprivation statistically explained the grade gradient
in depression at phase 5 for both men and women but their effects
were more marked in the case of men (after taking account of baseline
mental and physical health). Social support and life events were
also related to depression score, but varied little by employment
grade and so did not contribute as much as work characteristics
and material deprivation to the explanation of the grade gradient
in depression.
- Common factors
- including work characteristics, health behaviours and material
deprivation - contribute to the grade gradient in both physical
health (physical functioning) and depression. Work characteristics
were the most important explanatory factors for gradients in mental
health and health behaviours were most important for physical
health; perceived material problems also explained more of the
grade gradient in depression for women than they did for men.
Civil servants in the lower grades were more likely to experience
both physical and mental ill health. But common risk factors explained
only about 15% of the association between physical and mental
ill health. The most important of these were work characteristics
and material conditions. Pre-existing physical illness increased
risk of developing mental ill health and vice versa.
- There was
evidence that early life factors also played a role in the aetiology
of depression. One in ten men and one in five women stated that
they were separated from their mother for a year or more in childhood.
About 40% experienced at least one of seven situations relating
to emotional deprivation and a similar proportion reported experiencing
material deprivation. Those in low employment grades were more
likely to have experienced emotional or material deprivation in
childhood. Both were significantly related to phase 5 depression
score after adjustment for employment grade. However, employment
grade gradients in depression were only reduced by 7% after adjustment
for early life influences.
- The qualitative
study suggested that partner's employment status may have different
effects on the mental health and well-being of women compared
to men. The quantitative analyses confirmed that partner's employment
status was related to phase 5 depression in both men and women
- but that there were gender differences. Men whose partners worked
part-time or who were at home caring for the family had lower
depression scores than those whose partners worked full-time.
Men whose partners moved from caring for the family to full-time
employment had higher depression scores. For women, having an
unemployed partner was associated with higher depression scores
and having a partner who became unemployed was associated with
an increased depression score.
- The qualitative
interviews highlighted how negative perceptions of the workplace
- more common in lower grades - were exacerbated by isolation
and exclusion. Integration into co-operative work groups was linked
to job satisfaction, and was beneficial for reducing stress when
facing difficulties, or coping collectively with organisational
change. Experiencing stressors in both home and work environments
could be especially damaging for mental health. This suggests
that there may be a sliding social class scale whereby co-incidence
of stressors, and the balance of resources and stressors, leads
to mental illness.
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