Systematic Review and Meta-Analysis of Work Environment and Depressive Symptoms

R E S E A R C H A R T I C L E Open Access
A systematic review including meta-analysis
of work environment and depressive symptoms
Töres Theorell1,2* , Anne Hammarström 3
, Gunnar Aronsson 4
, Lil Träskman Bendz 5
, Tom Grape6 , Christer Hogstedt7 ,
Ina Marteinsdottir 8 , Ingmar Skoog 9 and Charlotte Hall 10
Abstract
Background: Depressive symptoms are potential outcomes of poorly functioning work environments. Such
symptoms are frequent and cause considerable suffering for the employees as well as financial loss for the employers.
Accordingly good prospective studies of psychosocial working conditions and depressive symptoms are valuable.
Scientific reviews of such studies have pointed at methodological difficulties but still established a few job risk factors.
Those reviews were published some years ago. There is need for an updated systematic review using the GRADE
system. In addition, gender related questions have been insufficiently reviewed.
Method: Inclusion criteria for the studies published 1990 to June 2013: 1. European and English speaking countries. 2.
Quantified results describing the relationship between exposure (psychosocial or physical/chemical) and outcome
(standardized questionnaire assessment of depressive symptoms or interview-based clinical depression). 3. Prospective
or comparable case-control design with at least 100 participants. 4. Assessments of exposure (working conditions) and
outcome at baseline and outcome (depressive symptoms) once again after follow-up 1-5 years later. 5. Adjustment for
age and adjustment or stratification for gender.
Studies filling inclusion criteria were subjected to assessment of 1.) relevance and 2.) quality using predefined
criteria. Systematic review of the evidence was made using the GRADE system. When applicable, meta-analysis of
the magnitude of associations was made. Consistency of findings was examined for a number of possible
confounders and publication bias was discussed.
Results: Fifty-nine articles of high or medium high scientific quality were included. Moderately strong evidence
(grade three out of four) was found for job strain (high psychological demands and low decision latitude), low
decision latitude and bullying having significant impact on development of depressive symptoms. Limited
evidence (grade two) was shown for psychological demands, effort reward imbalance, low support, unfavorable
social climate, lack of work justice, conflicts, limited skill discretion, job insecurity and long working hours. There
was no differential gender effect of adverse job conditions on depressive symptoms
Conclusion: There is substantial empirical evidence that employees, both men and women, who report lack of
decision latitude, job strain and bullying, will experience increasing depressive symptoms over time. These
conditions are amenable to organizational interventions.
Keywords: Depression, Work stress, Prevention, Ergonomic, Toxicology
* Correspondence: [e-mail]
1
Stress Research Institute, Stockholm University, SE-106 91 Stockholm,
Sweden
2
Department of Neuroscience, Karolinska Institutet, SE- 171 77 Stockholm,
Sweden
Full list of author information is available at the end of the article
© 2015 Theorell et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License
(http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium,
provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://
creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Theorell et al. BMC Public Health (2015) 15:738
DOI 10.1186/s12889-015-1954-4

Background
Depressive symptoms are potential outcomes of poorly
functioning work environments. Such symptoms are fre-
quent and may cause considerable suffering for the em-
ployees themselves as well as financial loss for the
employers. Accordingly good prospective studies of psy-
chosocial working conditions and depressive symptoms are
valuable.
Several reviews including prospective studies of
psychosocial factors at work in relation to depression
have been published. Bonde [1] concluded that there
were consistent findings that perception of adverse psy-
chosocial factors in the workplace is related to an ele-
vated risk of subsequent depressive symptoms or major
depressive episode but also that methodological limita-
tions preclude causal inference. Netterström et al. [2]
made a similar conclusion but pointed out that studies
are needed that assess in more detail the duration and
intensity of exposure necessary for developing depres-
sion. The conclusions in a review by Siegrist from the
same year [3] were similar. Also, Michie and Williams
[4] concluded that” many of the work related variables
associated with high levels of psychological ill health, are
potentially amenable to change which has been shown
in intervention studies that have successfully improved
psychological health and reduced sickness absence”. A
review of psychosocial and health effects of workplace
reorganization by Egan et al. [5] concluded that” some
organizational-level participation interventions may
benefit employee health, as predicted by the demand-
control model”. However, several other psychosocial
exposures should be examined more in detail.
Most of the work environment reviews published so far
have not been confined to depression only - they have
included for instance stress related disorders, psychologic-
ally related sick leave and suicide or combinations [4, 6–8]
as outcomes, and it has sometimes been difficult to disen-
tangle them. Studied work environment factors have
mostly been limited to psychosocial factors although two
reviews have included physical/chemical/ergonomic expo-
sures as well. The conclusion from them [4, 7] was that
the evidence for physical/chemical/ergonomic exposures
is limited and inconclusive. Nieuwenhuijsen et al. [8] pub-
lished a review of the effects of the psychosocial environ-
ment on risk of stress-related disorders (SRDs) and
concluded that there is” strong evidence that high job de-
mands, low job control, low co-worker support, low
supervisor support, low procedural justice and a high ef-
fort- reward imbalance predicted the incidence of SRDs”.
In summary, the evidence about the negative impact
of certain work environments for depressive symptoms
is accumulating but so far there has been no review
taking the entire spectrum of adverse working condi-
tions into account and at the same time focusing on
depressive conditions/symptoms as outcome. Most of
the reviews have used multiple kinds of mental health
outcomes. However, depression is the most widely re-
ported outcome in the field of mental health in epi-
demiological research. Depressive symptoms are well
understood in psychiatry which has resulted in a large
number of studies. Accordingly this outcome should
provide a good basis for a focused systematic review. As
far as the authors know there is no published study that
has used the international GRADE system [9] for evalu-
ating the evidence in this field. In addition there is a
need for a systematic review utilizing the most recent
developments in search technology.
An important aspect of the systematic review process
is to systematically and transparently assess the scientific
evidence. We have chosen to use the internationally rec-
ognized GRADE- system for scientific evaluation. The
GRADE system uses four levels of evidence, namely
High, Moderate, Limited and Very Limited. We are well
aware that the system has been developed primarily for
assessing interventions in a health care context, but the
system has been adapted to epidemiological evaluation.
Beside the transparency, an advantage is that the
GRADE system [9] - a system often applied in reviews
conducted within the Cochrane Collaboration - is in-
creasingly used internationally e.g., by the World Health
Organization. Hence results from systematic reviews can
be more easily compared.
Time has elapsed since most of the previous reviews
were published and new studies are published continu-
ously. The most relevant reviews were published in 2008.
They pointed at several methodological shortcomings,
and it is not known whether researchers more recently
have tried to address the identified scientific problems. In
particular, the reviews have pointed at the paucity of stud-
ies on physical/chemical/ergonomic exposures.
A topic that has not been addressed sufficiently in pre-
vious reviews is gender in the relationship between
working conditions and the development of depressive
symptoms. Are the associations different for men and
women?
Aim of the study
The aim of this study was to provide systematically
graded evidence for possible associations between work
environment factors and near-future development of de-
pressive symptoms
Methods
The present review was based upon studies with a pro-
spective design and is focused on the relationship
between working conditions and development of symp-
toms of depression among the employees.. We con-
ducted and funded this systematic review within the
Theorell et al. BMC Public Health (2015) 15:738 Page 2 of 14

framework for the Swedish Council on Health and Tech-
nology Assessment, a public agency with the charge of
providing impartial and scientifically reliable information
to decision makers and health care providers [10].
Search strategy
Systematic literature search was performed in the following
data bases: PubMed, Embase, Psycinfo, Arbline (Swedish
database), Cochrane library and NIOSHTIC-2. A combin-
ation of controlled search words (e.g., MeSH) and free- text
words was used. The search strategy for the outcome was
performed for mesh terms (‘Depression’ and ‘Depressive
Disorders’) and as free search in title and abstract (depress*
and dysthym*). The whole search strategy is available at
http://www.sbu.se/upload/Publikationer/Content0/1/223E/
Inclusion%20criteria_occupational%20exposure_depression
_burnout.pdf. We only accepted as articles in scientific
journals with independent reviews.
Inclusion criteria
The inclusion criteria for studies were:
1. The study should have examined the importance of
the work environment for depressive symptoms.
Our review was not confined to any specific kind of
work environment factors. Physical/chemical/
ergonomic exposures as well as psychosocial factors
were screened.
2. The study should be relevant for Swedish conditions
and focused on people at work. Work environments
in Europe, North America, Australia and New
Zealand were included.
3. In the study symptoms of depression should have
been analyzed. These should have have been
certified through diagnostic investigation or with
established scales. We argued that not only
diagnosed major depression, but also milder states
with depressive symptoms are relevant since
depressive feelings give rise to suffering, increase the
risk of long term sick leave and cause productivity
decline and quality loss in work places [11]. Thus,
our review included both studies with standardized
clinical interviews regarding diagnosed depression
and studies based upon rating scales on depressive
symptoms. As diagnosed depression is also to a large
extent based on symptoms we decided that the most
accurate naming of the outcome of our review was
depressive symptoms. A few studies were based
upon either sick leave data or registered anti-
depression medication as outcome but these studies
are not included in this review.
4. A minimum of 100 persons should have been
included in the exposed group and the results were
controlled for at least age and gender.
5. The study should have been published between the
years 1990 and (June) 2013 and written in English.
6. Prospective or comparable case-control design. Only
prospective cohort, case control (with design equivalent
to prospective) and randomized intervention studies
with at least 100 participants were included. By case
control studies with “design equivalent to prospective”
we are referring to studies with strict definition of cases
recruited in a representative way in the same
population as the control group.
Assessments of exposure should have been made be-
fore disease onset.
Doublets were systematically identified and only the
most relevant publication in a doublet was included.
Analyses of relevance and quality
Abstract screening and full-text assessment were con-
ducted by a specialist in occupational medicine and a
psychiatrist.
After that, the scientific experts started their examin-
ation. Pre-set evaluation forms were used. The experts
judged relevance and quality of the studies on the basis
of the relevance/quality criteria, their experience as re-
searchers and their knowledge of the field. Accordingly
they were recruited among Swedish academic high
ranking specialists in fields of relevance for the process,
namely psychiatry (three), epidemiology and stress re-
search (three), work psychology (one) and family prac-
tice (one). This group was divided into pairs with as
widely differing specialty in the pair as possible. In the
following process, the articles remaining in the process
were randomly assigned to the four pairs (with avoid-
ance of author bias). Concordance in judgments of rele-
vance and quality was trained. After the training
session, each member of the pair did the assessments
separately, and then discordances were discussed within
the pair. If disagreement remained another pair was
asked to make an independent judgment. If that deci-
sion was in disagreement with the first group, we made
the decision in the whole group.
In the first expert phase, the group judged relevance.
Relevance criteria are presented in http://www.sbu.se/up-
load/Publikationer/Content0/1/223E/Inclusion%20criteria
_occupational%20exposure_depression_burnout.pdf.
Secondly, we performed a quality assessment. Three
levels of quality rating were used, (low, medium high
and high quality) and in the final grading process only
those with medium high and high quality were accepted.
Accordingly the important dividing line was between
poor and medium high quality whereas the distinction
between medium high and high was less crucial. Studies
on the borderline between low and medium high quality
were accordingly re-examined by the whole group. A list
Theorell et al. BMC Public Health (2015) 15:738 Page 3 of 14

of relevant articles meeting the inclusion criteria judged
to be of low quality is available at http://www.sbu.se/up-
load/Publikationer/Content0/1/223E/Inclusion%20cri-
teria_occupational%20exposure_depression_burnout.pdf
The following aspects of quality were considered:
1.) Representativeness of study sample.
Representativeness and ways of defining and
recruiting the sample as well as attrition in different
steps were considered in the quality rating.
Statistical considerations and an insightful discussion
of possible consequences of a possible systematic
drop-out for findings were required in case of
marked drop-out problems.
2.) Confounding. Age and at least some aspect of
socioeconomic conditions should have been
considered. Gender specific analyses were preferred
but when such analyses were not available,
adjustment for gender was required. Life habits such
as smoking habits and alcohol consumption were
not taken into account as confounders in our
review.
3.) Prospective data collection. All results of the studies
included in this review (apart from case-control
studies) are based upon assessments of exposure and
depressive symptoms in the beginning and of the
depressive symptoms again at least one year later. In
the calculations of associations a design with either
exclusion of subjects with depressive symptoms at
baseline or adjustment for baseline level of depressive
symptoms was required. Qualified statistics and
thorough discussion of longitudinal data rendered
higher quality ratings.
4.) For both exposure and outcome assessment,
psychometrically standardized and validated
methods were required. Well established methods
enable comparison across studies and therefore
contributed to higher quality rating.
5.) Designs that enable the analysis of a dose response
relationship contributed to a high quality rating. For
instance, in a few studies the work environment was
assessed in two or three subsequent waves and the
development of depressive symptoms followed up
after the last assessment. Exposure to given work
environment factor on one, two or three occasions
could be regarded as a progressive duration of
exposure and was regarded as equivalent of a dose-
response analysis.
Even between studies of specific work environment
factors there were differences with regard to operationa-
lization of exposure. Examples are job strain (combin-
ation of high psychological demands and low decision
latitude) and effort reward imbalance (combination of
high effort and poor reward). Since the overall aim of
the present study was to grade total evidence, not to as-
sess magnitude of associations, and since it was impos-
sible to re-construct operationalizations in such a way
that they would match one another we decided to use
the definitions presented by the authors themselves and
to mostly abstain from assessment of overall magnitude
of the different relationships.
The final list of studies judged to be of high or
medium high quality is listed in Appendix.
GRADE procedure
An important aspect of the systematic review process
was to systematically and transparently assess the scien-
tific evidence. According to the GRADE instructions
explicit consideration should be given to each of the
GRADE criteria for assessing the quality of evidence
(risk of bias/study limitations, directness, consistency of
results, precision, publication bias, magnitude of the ef-
fect, dose-response gradient, influence of residual plaus-
ible confounding and bias “antagonistic bias”) although
different terminology may be used. For level 4 (=High),
randomized trials are required and there were no such
published relevant studies in our search. For observa-
tional studies of the kind included in the present review,
the highest possible grade is Moderate = 3 if there is
sufficient reason for an upgrading from the normal level
for such studies of 2 (=Limited). Level 1 (=Very limited)
corresponds to evidence based on case reports and case
series or on reports downgraded evidence from observa-
tional studies.
We allowed for upgrading the scientific evidence
when there was strong coherence of results between
studies - according to the most recent guidelines [12].
Accordingly when there were many published observa-
tional studies of medium high or high quality with
homogenous results (almost all pointing in the same
direction although all findings may not have been statis-
tically significant) the evidence was graded on level 3
(two exposures, high decision latitude as protective and
job strain as negative exposure, see below). Level 3 can
also be used according to the GRADE system even when
there are relatively few studies if there are unanimous
findings with high odds ratios (above 2.0). This occurred
for one exposure – bullying (see below).
Meta-analyses/Forest plots
In the studies results were reported as calculations of
association, e.g., expressed as odds ratios, from mul-
tiple logistic regression, multivariate correlations or
multiple linear regression coefficients. Whenever pos-
sible, the results were transformed into multiple logis-
tic regression odds ratios. Forest plots were used for
visual interpretation. To assist in illustrating the
Theorell et al. BMC Public Health (2015) 15:738 Page 4 of 14