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Working Overtime is Associated With Anxiety
and Depression: The Hordaland Health Study
Elisabeth Kleppa, MD
Bjarte Sanne, MD, PhD
Grethe S. Tell, PhD, MPD
Learning Objectives
•Compare Hospital Anxiety and Depression Scale scores of anxiety (HADS-A)
and depression (HADS-D) as well as the estimated prevalence rates of
“possible” anxiety and depressive disorders in 1350 overtime workers (more
than 40 hours per week) and a reference group of 9092 employees not working
overtime.
•Contrast the findings in male employees working 41 to 48 hours per week
(moderate overtime) with those in employees working 49 to 100 hours a
week (very much overtime).
•Describe the characteristics of women working overtime when compared to
those in the reference group.
Abstract
Objective: To examine whether long work hours are associated with increased
levels and prevalences of anxiety and depression. Methods: Overtime workers
(n ⫽1350) were compared with a reference group of 9092 workers not working
overtime regarding anxiety and depression by means of the Hospital Anxiety and
Depression Scale. Self-reported information on various work-related factors,
demographics, lifestyle, and somatic health was included. Results: Overtime
workers of both genders had significantly higher anxiety and depression levels and
higher prevalences of anxiety and depressive disorders compared with those
working normal hours. Findings suggest a dose-response relationship between
work hours and anxiety or depression. Conclusions: Working overtime is
associated with increased levels of anxiety and depression. The working groups
differed significantly regarding several factors including income and heavy
manual labor. (J Occup Environ Med. 2008;50:658 – 666)
Earlier studies have concluded that
there is sufficient evidence to raise
concerns about the risks to health
and safety of employees who have
long working hours.
1–3
This was es-
pecially discussed when The Euro-
pean Community Directive on
Working Time from 1993
4
was pub-
lished. The directive contained sev-
eral requirements related to working
hours, for example the right of em-
ployees to refuse to work more than
48 hours per week.
1
However, as
Spurgeon et al
2
concluded, much of
the research in this area has focused
on the problems of shift work and
there is much less information about
the effects of working long hours.
The few articles that are published
on this topic have concluded that
more studies are needed, and espe-
cially studies focusing on the relation
between working overtime and men-
tal health status.
1,2
Sanne et al
5
discussed occupa-
tional differences in levels of anxiety
and depression in the Hordaland
Health Study. This article expands
our previous findings, and examines
in more detail issues related to over-
time work. In particular, the levels
and prevalences of anxiety and de-
pression in groups working overtime
are compared with those working
normal hours. The study was carried
out in a large Norwegian population-
based sample of men and women
living and working in both urban and
rural settings.
The following research questions
were posed:
1. Are long work hours associated
with increased levels and preva-
lences of anxiety and depression? If
From the Medical Faculty (Dr Kleppa), University of Bergen, Bergen, Norway; Centre for Child and
Adolescent Mental Health (Dr Sanne), University of Bergen, Bergen, Norway; and Department of
Public Health and Primary Health Care (Dr Tell), University of Bergen, Bergen, Norway.
Elisabeth Kleppa and coauthors have no financial interest related to this research.
Address correspondence to: Elisabeth Kleppa, Medical Faculty, University of Bergen, Bergen,
Norway; E-mail: elisabeth.kleppa@student.uib.no.
Copyright © 2008 by American College of Occupational and Environmental Medicine
DOI: 10.1097/JOM.0b013e3181734330
CME Available for this Article at ACOEM.org
658 Working Overtime is Associated With Anxiety and Depression •Kleppa et al
so, does this association represent a
dose-response relationship?
2. Do workers with normal and long
work hours differ with regard to
other work related factors, demo-
graphic and lifestyle indicators, and
somatic health problems?
3. To what extent do possible differ-
ences found in (2) explain the even-
tual differences found in (1)?
Materials and Methods
Study Population
The Hordaland Health study 1997
to 1999 (HUSK) was conducted as a
collaboration between the National
Health Screening Service, the Uni-
versity of Bergen and local health
services. The study population in-
cluded 29,400 individuals born be-
tween 1953 and 1957 who resided in
Hordaland county (of Western Nor-
way) on December 31, 1997. A total
of 8598 men and 9983 women par-
ticipated, yielding a participation rate
of 57% for men and 70% for women.
Participants filled out question-
naires and underwent a brief health
examination, as has previously been
reported.
5
The present study encompassed
only those participants who reported
to have at least 2 hours of paid work
per week and valid Hospital Anxiety
and Depression Scale(HADS)
scores. These selection criteria gave
a total number of 13,975 individuals.
The number of participants working
normal hours (35 to 40 and 32 to 40
hours/wk for men and women, re-
spectively) and overtime (41 to 100
hours/wk) was 10,442.
Measurements
Anxiety and Depression. Levels of
anxiety and depression were as-
sessed by the HADS, which has been
found to perform well in assessing
symptom load and caseness of anxi-
ety and depressive disorders in both
somatic, psychiatric and primary
care patients, and in the general pop-
ulation.
6
Valid HADS scores were
defined as having answered at least
five of seven items on both the anx-
iety (HADS-A) and the depression
(HADS-D) sub-scales. Each item
was scored on a four-point scale
from 0 to 3, and the item scores were
added, giving sub-scale scores from
0 (minimum symptom level) to 21
(maximum symptom level). The
scores of those who filled in five or
six items were based on the sum of
completed items multiplied with 7/5
or 7/6, respectively.
Caseness (ie, “possible cases” of
HADS anxiety and depressive disor-
ders) was defined as a score of 8 or
above on HADS-A or HADS-D, as
this cutoff level has been shown to
give an optimal balance between
sensitivity and specificity on receiver
operating characteristic curves.
6
Work-Related Variables. Informa-
tion about number of paid work
hours per week (0 to 100 hours)
enabled the categorization of partic-
ipants into different groups. For both
genders, the reference group refers to
participants with normal work hours
(35 to 40 and 32 to 40 hours/wk for
men and women, respectively). The
overtime group consists of those
working 41 to 100 hours per week.
For men, this group was dichoto-
mized into “moderate overtime” (41
to 48 hours of work per week) and
“very much overtime” (49 to 100
hours of work per week), as a total
number of 48 hours of work per
week is the upper limit in the Euro-
pean Community Directive on
Working Time.
4
Because the number
of women working overtime was
rather small, this group was not di-
vided further.
Information on other work-related
factors included level of physical
activity at work (mainly sedentary
work/work demanding much walk-
ing with or without much lifting/
heavy manual labor), shift work,
night work or duties (yes/no), and
major occupation, which was manu-
ally classified according to Standard
Classification of Occupation
7
whose
structure is based on skill level, ie,
which technical and formal skills
that are normally required.
Demographics, Individual Life-
style, and Somatic Health. Informa-
tion concerning the following was
also reported: Educational attain-
ment, annual household income,
marital status, children (yes/no),
smoking, alcohol consumption, level
of leisure time physical activity,
musculoskeletal problems (pain or
stiffness of at least 3 months duration
in the last 12 months, resulting in
reduced work capacity or sick leave),
chronic somatic diseases (having
[had] myocardial infarction, angina
pectoris, hypertension, stroke,
asthma, chronic bronchitis, diabetes
mellitus, or multiple sclerosis), and
the physical composite score of the
SF-12 Health Survey as an indicator
of health-related quality of life.
Height and weight were measured
and body mass index (BMI, kg/m
2
)
was calculated.
Statistics
All analyses were stratified by
gender, due to different mean HADS
scores and a considerably different
distribution pattern of work hours
between genders. Univariate analysis
of variance (ANOVA) was used to
test the hypothesis of no differences
in mean HADS scores between over-
time workers and the reference
group, and between subgroups of
overtime workers. As Levene’s test
of equality of variances showed that
the variances differed significantly
between the groups for mean
HADS-D scores in most of the tests
performed, these analyses were re-
peated using the nonparametric
Kruskal-Wallis test. Unless other-
wise stated, the two methods gave
equivalent levels of significance.
Significance level was set to P⫽
0.05 with two-sided tests. All
HADS-A and HADS-D scores
throughout the article refer to mean
HADS scores.
Cross tabulations and
2
test or
Fisher exact test were used to exam-
ine if and how the groups differed
regarding prevalences of anxiety and
depressive disorders and regarding
work-related factors, demographics,
JOEM •Volume 50, Number 6, June 2008 659
lifestyle, and somatic health prob-
lems. Possible differences in anxiety
and depression caseness were also
examined by logistic regression.
ANOVA was used to adjust the
HADS-A and HADS-D scores for
possible confounders, primarily by
using two-way ANOVA. Then, be-
cause the differences in HADS
scores could not be explained by a
single variable, different models
were made for the simultaneous ad-
justment of several explanatory fac-
tors. The models were based on
themes (“work related,” “demo-
graphics,” “individual lifestyle,” and
“somatic health”; see Measurements
for details), the different variables’
explained variance (in one-way
ANOVA with the corresponding
HADS score as the dependent vari-
able) and on variables that differed
most between overtime workers and
reference group (Table 1). A similar
procedure was used to adjust case-
ness for possible confounders in lo-
gistic regression.
The dose-response relationship of
the association between working
hours and caseness of anxiety and
depressive disorders was further ex-
amined by Generalized Additive
Model curves.
The analyses were performed by
using SPSS for Windows, version
14.0 and SPLUS, version 6.1.
Ethics
The HUSK study protocol was
cleared by the Regional Committee
for Medical Research Ethics of
Western Norway and approved by
the Norwegian Data Inspectorate.
Each participant signed an informed
consent.
Results
General Findings
The distribution pattern of work
hours differed considerably between
genders. Women had considerably
shorter working weeks than men,
fewer worked overtime, and those
who did worked fewer hours over-
time than men (Fig. 1). Some 1099
men and 251 women worked more
than 40 hours per week (Table 1).
Overtime workers had significantly
higher HADS-A and HADS-D scores
and higher prevalences of “possible”
anxiety and depressive disorders than
the reference groups in both genders
(Table 2). Also those who had the
lowest annual household income had a
significantly higher prevalence of
“possible” anxiety and depressive dis-
orders for both genders. As for major
occupational grouping, the groups
with the lowest skill levels had signif-
icantly higher depression caseness in
both genders and anxiety caseness in
men (Tables 2 and 3). Table 2 also
shows HADS scores after stratification
by some factors, showing significant
differences in various groups, espe-
cially evident for income. Figure 2
shows that the associations between
HADS caseness and working hours are
U-shaped.
Characteristics of Men Working
41 to 100 Hours per Week
Compared with the reference
group, men working overtime had
significantly higher levels of
HADS-A and HADS-D and higher
prevalences of “possible” anxiety
and depressive disorders (Table 2).
Also, a larger proportion of the latter
group reported heavy manual labor
(13.6% vs 5.6%), shift work/night
work or duties, annual income above
NOK 500,000 a year (in 1999 equiv-
alent to EUR 60,168), occupations
with highest skill level and low lev-
els of leisure time physical activity
(Table 1).
Compared with workers in the ref-
erence group, a lower proportion of
men working overtime reported mus-
culoskeletal problems, and a higher
proportion had children.
Characteristics of Men Working
41 to 48 Hours per Week
Compared with the reference
group, men working moderate
overtime had a higher mean
HADS-A score, but not a signifi-
cantly higher prevalence of anxiety
disorder (Table 2). Further, a larger
proportion of the latter group worked
shifts or night work/duties, had oc-
cupations requiring the highest skill
level (64%, compared with 54% in
the reference group), had college/
university level education and was
more likely to earn more than
500,000 NOK a year (Table 1). Fi-
nally, a smaller proportion was
smoking daily and a higher propor-
tion had children compared with
workers in the reference group.
Characteristics of Men Working
49 to 100 Hours per Week
Compared with the reference
group, men working most overtime
showed significantly higher levels of
HADS-A and HADS-D (Table 2)
and higher prevalences of anxiety
and depressive disorders (some
21% of the group had “possible”
anxiety disorder; Table 2). Also, a
larger proportion of the latter group
reported to have heavy manual la-
bor (19% vs 6%), shift work or
night work/duties (39% vs 21%),
occupations with the lowest skill
level and an annual income above
500,000 NOK and below 200,000
NOK (Table 1). Finally, the level
of leisure time physical activity
was lower compared with those
working normal hours.
A Comparison of the Moderate
and the Very Much Overtime
Groups Among Men
Compared with the group working
moderate overtime, the men working
most overtime showed a significantly
higher HADS-D level and a higher
prevalence of “possible” anxiety disor-
der (Table 2). Further, a larger propor-
tion of the latter group reported low
skill level (40% vs 23%), heavy man-
ual labor (19% vs 7%), shift work/
night work/duties and daily smoking,
and a higher proportion in this group
had an annual income under 200,000
NOK. Finally, the very much overtime
workers reported lower educational at-
tainment and a lower level of leisure
660 Working Overtime is Associated With Anxiety and Depression •Kleppa et al
time physical activity compared with
those working moderate overtime.
Characteristics of Women
Working Overtime
Compared with the reference
group, women working overtime
showed significantly higher levels
of HADS-A and HADS-D and
higher prevalences of possible anx-
iety and depressive disorders (Ta-
ble 2). Overtime workers were
more prone to report either the
highest or the lowest skill level
compared with the reference group.
Also, a larger proportion of the
overtime group had shift work/
night work/duties, a higher level of
physical activity at work and a
higher BMI (Table 1). Finally,
those working long hours reported
TABLE 1
Characteristics of Overtime and Regular Workers in The Hordaland Health Study (%)
Variables/Categories
Men Women
Reference Group
35– 40 h/w,*
nⴝ5,113
Overtime Workers Reference Group
32– 40 h/w,
nⴝ3,979
Overtime Workers
41–100 h/w,
nⴝ251
41–100 h/w,
nⴝ1,099
41– 48 h/w,
nⴝ458
49 –100 h/w,
nⴝ641
Major occupational
groups†‡§㛳¶#
0 –3 53.7 57.7 64.3 52.9 45.7 52.8
4 –5 13.4 9.8 13.0 7.5 45.3 31.7
6 –9 32.9 32.6 22.7 39.7 9.0 15.4
Level of physical activity
at work‡§㛳#
Mainly sedentary work 53.8 50.0 53.9 46.9 48.3 31.9
Much walking and/or
much lifting
40.6 36.4 39.6 34.0 51.3 66.8
Heavy manual labor 5.6 13.6 6.5 19.1 0.4 1.3
Shiftwork, night work, or
duties (yes)‡§㛳¶#
21.3 35.4 30.1 39.4 21.6 31.7
Level of education§¶
Less than A-levels/high
school
52.0 48.4 43.9 51.6 47.5 52.2
(Equivalent to) A-levels/high
school
9.3 10.3 9.4 10.9 11.3 8.8
College/university 38.8 41.3 46.7 37.4 41.2 39.0
Annual household income
in NOKद#**
⬍200.000 3.9 4.0 1.8 5.7 12.0 15.4
ⱖ200.000 and ⬍500.000 69.7 62.1 64.8 60.3 58.9 54.8
ⱖ500.000 26.4 33.8 33.5 34.1 29.1 29.9
Having children (yes)ঠ86.0 89.2 90.4 83.3 86.9 87.6
Daily smoking (yes)§¶ 33.7 33.1 28.8 36.2 35.9 39.4
Leisure time physical
activity‡§㛳#
Low 4.0 6.8 3.3 9.3 2.6 3.6
Medium 44.2 43.4 43.5 43.4 46.8 55.6
High 51.8 49.8 53.2 47.3 50.6 40.8
Musculoskeletal problems
(yes)
†
10.4 8.3 8.4 8.2 15.1 15.3
Body mass index (kg/m
2
)㛳
⬎22.8 (1st quartile) 13.0 12.3 13.1 11.7 36.3 27.1
22.8 –27.4 (2nd–3rd
quartile)
56.2 55.7 54.6 56.5 45.0 52.2
⬎27.4 (4th quartile) 30.7 32.0 32.3 31.8 18.6 20.7
*h/w: Total number of hr of work per week.
†See Table 2, footnote §.
‡Men: The group working 41–100 hour per week differed significantly from the reference group.
§Men: The group working 41– 48 hour per week differed significantly from the group working 49–100 hour per week.
㛳Women: The overtime group differed significantly from the reference group.
¶Men: The group working 41– 48 hour per week differed significantly from the reference group.
#Men: The group working 49 –100 hour per week differed significantly from the reference group.
**In 1999, NOK 200,000 and 500,000 were equivalent to EUR 24,067 and 60,168, respectively.
JOEM •Volume 50, Number 6, June 2008 661
a lower level of leisure time phys-
ical activity compared with the ref-
erence group.
Generally there were fewer signif-
icant differences for women than for
men, and the differences were less
pronounced. It is also notable that
there were no significant differences
between the groups regarding educa-
tional attainment, annual household
income, parity, daily smoking, and
musculoskeletal problems.
Could the Differences in HADS
Levels and Caseness be
Explained by Other Factors?
Overtime workers had signifi-
cantly higher levels of anxiety and
depression than the reference groups
(Table 3). The differences in
HADS-A and HADS-D levels be-
tween overtime workers and refer-
ence groups could not be explained
by any of the measured potential
confounders, whether single factors
or combinations of factors. When ex-
amining the differences in odds ratios
(ORs) for possible confounding,
none of the adjusted ORs differed
significantly from the unadjusted
ones. Therefore, only unadjusted
values are referred in Table 3.
Discussion
The study showed that both men
and women working overtime had
higher anxiety and depression lev-
els and prevalences of “possible”
anxiety and depressive disorders
compared with those who worked
normal hours. Compared with the
reference group, men working very
much overtime had higher preva-
lences of “possible” depression and
anxiety disorders. Compared with
men working 41 to 48 hours per
week, the group working 49 to 100
hours reported more “heavy man-
ual labor” and shift work, and had
lower skill level and education.
Men working 41 to 48 hours per
week had higher educational level,
income, and skill level than the
reference group. Differences in
anxiety and depression levels and
caseness between overtime workers
and the reference groups could not
be explained by factors measured
in the study.
Study Strengths and Limitations
This population-based study is, to
our knowledge, the largest study so
far to examine levels of anxiety and
depression in overtime workers, and
one of the few that have included a
measure of anxiety. The assessment
of both anxiety and depression levels
is important, due to the high correla-
tion between anxiety and depressive
symptoms.
6
The large sample size allowed
stratification on gender. The gender
specific analyses are important due
to the different HADS scores and the
different distribution of work hours
between genders. Further, the com-
parison between groups with differ-
ent numbers of working hours per
week has, to our knowledge, not
been previously addressed. Workers
from a large range of occupations
were included, strengthening the
generalizability of our findings. Fi-
nally, the relatively large number of
other relevant variables included al-
lowed the investigation of possible
explanatory factors in the association
between overtime work and anxiety
and depression, not possible in most
prior studies.
The most important limitation of
the study is its cross-sectional de-
sign. However, the study results con-
firmed the hypothesis that overtime
workers are at risk for anxiety and
depression. The narrow age ranges
reduce the generalizability of the
findings. On the other hand, because
of the large sample size and the age
homogeneity, it was possible to di-
vide male overtime workers into two
groups.
The moderate participation rate war-
rants some remarks: Nonresponders to
surveys have been found to have
higher prevalences of mental disor-
ders.
8,9
The “Healthy Worker Effect”
is well known,
10
and also in our mate-
rial, the unemployed had considerably
higher anxiety and depression levels
than workers. Thus in the present
study, it is possible that the proportion
of employed individuals was higher
among those participating compared
with those who did not. On the other
hand, according to our findings, over-
time workers are more prone to anxi-
ety and depression than those working
normal hours. In addition, those work-
ing long hours may have had less time
available to participate in the study.
Thus, it is possible that those working
long hours were underrepresented in
our study, and accordingly, that the
effect of overtime work on anxiety and
depression was underestimated.
Fig. 1. The distribution of working hours for men and women (with mean and 95% confidence
intervals) in the Hordaland Health Study.
662 Working Overtime is Associated With Anxiety and Depression •Kleppa et al
The HADS does not provide defi-
nite diagnoses of anxiety and depres-
sive disorders. However, because of
the Healthy Worker Effect, it is to be
expected that the main part of the
variation in HADS scores in our
sample was found in the sub-clinical
area (since those working would be
expected to be relatively healthy).
This strengthens the argument for
comparing levels of symptom load in
addition to comparing prevalences of
cases.
Relation to Literature Findings
Congruent with our results, Want-
anabe et al
11
found an association
between self-rated symptoms of de-
pression and long working hours.
Also Nishikitani et al
12
found that
working overtime was associated
with increased Hamilton Depression
Scale scores. Sparks et al.’s meta-
analysis
1
found increased mental
health symptoms for the group work-
ing long hours.
Shields et al
3
examined results from
two surveys conducted with a 2-year
interval. They found that women
working long hours in the first survey
were at risk for subsequently develop-
ing a depressive episode. For men, no
relationship was found between long
working hours and depression.
The higher level of depression in
men than in women in our study
agrees with the findings from the
large Norwegian population-based
HUNT study, where the OR for
HADS depression caseness was sig-
nificantly higher in men compared
with women.
13
This may be due to
questionable validity regarding gen-
der differences in HADS-D.
14
A novel finding in this study was the
high levels of anxiety for both men and
women who worked overtime, espe-
cially among the men working most
overtime. Another new finding was the
observation that men working moder-
ate overtime showed a higher
TABLE 2
HADS* Scores (Mean and 95% Confidence Interval) and Caseness† (Cases; %) According to Some Main Characteristics of
Overtime and Regular Workers in the Hordaland Health Study
Men Women
HADS-A HADS-D HADS-A HADS-D
Mean Score
Cases
(%) Mean Score
Cases
(%) Mean Score
Cases
(%) Mean Score
Cases
(%)
No. of work hr/wk
Reference group‡§ 4.21 (4.13– 4.29) 13.4 3.34 (3.26 –3.42) 9.1 4.63 (4.53– 4.73) 17.6 2.79 (2.71–2.88) 7.0
41–100 4.70 (4.51– 4.88) 17.3 3.77 (3.59 –3.95) 12.5 5.22 (4.76 –5.67) 23.5 3.31 (2.92–3.71) 10.8
41– 48 4.60 (4.33–4.88) 12.7 3.56 (3.28 –3.83) 11.6
49 –100 4.76 (4.51–5.02) 20.6 3.92 (3.68 – 4.16) 13.1
Major occupational groups㛳¶
0 –3 4.18 (4.09– 4.28) 13.3 3.14 (3.05–3.24) 7.9 4.65 (4.53–4.77) 18.1 2.78 (2.68 –2.88) 6.6
4 –5 4.42 (4.21–4.63) 15.1 3.43 (3.22–3.63) 10.6 4.74 (4.63–4.85) 17.9 2.89 (2.80 –2.98) 7.5
6 –9 4.46 (4.33–4.60) 15.6 3.92 (3.79 – 4.05) 12.9 5.18 (4.95–5.42) 23.1 3.41 (3.20 –3.61) 10.6
Level of physical activity at work#
Mainly sedentary work 4.24 (4.14 – 4.35) 13.7 3.31 (3.21–3.41) 9.1 4.64 (4.51– 4.76) 18.2 2.80 (2.69–2.90) 7.3
Much walking and/or much lifting 4.32 (4.20– 4.44) 14.5 3.45 (3.34 –3.56) 10.4 4.79 (4.69– 4.89) 18.4 2.94 (2.86 –3.03) 7.5
Heavy manual labor 4.66 (4.35–4.96) 16.6 4.14 (3.84 – 4.44) 12.9 4.67 (3.72–5.61) 22.7 3.37 (2.41– 4.32) 11.4
Shiftwork, night work or duties
Yes 4.37 (4.22– 4.52) 15.8 3.61 (3.47–3.76) 11.0 4.76 (4.61– 4.91) 18.6 2.96 (2.84 –3.08) 7.8
No 4.29 (4.21– 4.38) 13.8 3.39 (3.31–3.47) 9.6 4.76 (4.67–4.85) 18.7 2.90 (2.82–2.97) 7.5
Level of education#
Less than A-levels/high school 4.43 (4.32–4.53) 15.0 3.68 (3.58 –3.78) 11.2 4.85 (4.74– 4.95) 18.6 3.00 (2.91–3.09) 8.0
(Equivalent to) A-levels/high school 4.47 (4.23–4.71) 14.0 3.52 (3.30 –3.74) 9.7 4.84 (4.60–5.09) 20.5 2.96 (2.76 –3.15) 8.3
College/university 4.14 (4.02–4.26) 13.6 3.13 (3.02–3.24) 8.4 4.62 (4.50– 4.75) 18.2 2.78 (2.68 –2.89) 6.7
Annual household income in NOK**§
⬍200.000 5.28 (4.87–5.69) 25.9 4.53 (4.14 –4.92) 21.0 5.55 (5.33–5.78) 25.7 3.48 (3.28 –3.67) 11.7
ⱖ200.000 and ⬍500.000 4.39 (4.30 –4.48) 14.7 3.60 (3.51–3.68) 10.4 4.75 (4.65–4.85) 18.4 2.96 (2.87–3.04) 7.6
ⱖ500.000 3.96 (3.83–4.10) 11.5 2.87 (2.75–3.00) 6.5 4.37 (4.22– 4.51) 15.6 2.45 (2.33–2.56) 4.7
*Hospital Anxiety and Depression Scale; HADS-A: anxiety score, HADS-D: depression score.
†Caseness: “Possible” cases of anxiety and depression (HADS-A and HADS-D scores ⱖ8, respectively).
‡Reference group: those working 35– 40 and 32–40 hr/wk for men and women, respectively.
§Caseness in HADS-A and HADS-D differed significantly between the groups in both genders.
㛳0 –3: The groups with the highest skill levels (0: Armed forces, 1: Legislators/senior officials/managers, 2: Professionals, and 3:
Technicians/associate professionals). 4 –5: The groups with intermediate skill levels (4: Clerks and 5: Shop/market sales and service workers).
6 –9: The groups with the lowest skill levels (6: Agricultural/forestry/fishery workers, 7: Craft and related trades workers, 8: Plant/machine
operators, assemblers, and 9: Elementary occupations).
¶Caseness in HADS-A and HADS-D differed significantly between the groups for women and in HADS-D for men.
#Caseness in HADS-D differed significantly between the groups for men.
**In 1999, NOK 200.000 and 500.000 were equivalent to EUR 24,067 and 60,168, respectively.
JOEM •Volume 50, Number 6, June 2008 663
HADS-A score but a lower prevalence
of anxiety disorder, compared with the
reference group. This could indicate
that these workers have a higher stress
level, but under the cutoff for anxiety
disorder.
Selection or “Wear and Tear”?
Increased levels of anxiety and
depression may be due to one or
more of the following: 1) An in-
creased selection into working over-
time of individuals prone to anxiety
or depression. Congruent with this
hypothesis, Wantanabe et al
11
in
their cross-sectional study found that
type A subjects had longer weekly
working hours and higher depression
scores than non-type A subjects and
that those having the highest depres-
sion scores worked longer hours than
those working fewer hours. 2) A
decreased selection out of jobs requir-
ing long working hours of individuals
prone to anxiety or depression. Ac-
cording to Waghorn and Chant
study,
15
one of the most common
employment restrictions among per-
sons with ICD-10 anxiety disorders
was difficulty in changing jobs. In
our material, we found that those
working much overtime, in addition
to having increased anxiety (and
depression) scores, also had less ed-
ucation and lower skill level com-
pared with the reference group,
which could mean that they had
fewer opportunities to change work.
3) A consequence of “wear and
tear”: Job conditions, as a major
source of environmental influence,
may influence the development of
anxiety and depression.
16,17
At least
three mechanisms have been sug-
gested as mediators of the “wear and
tear” effects.
18
A behavioral or lifestyle mecha-
nism: Poor lifestyle habits such as
cigarette smoking and use of alcohol
has been found to be associated with
long working hours.
19,20
It has been
suggested that the impact of job de-
mands (ie, long working hours) on
work related stress are mediated by a
set of maladaptive coping behaviors
and responses.
20
In our study, men
working much overtime smoked sig-
nificantly more than those working
less overtime. However, there was
no significant difference in alcohol
consumption between the different
working groups.
For both genders, overtime work-
ers reported less leisure time physi-
cal activity and women working long
hours had a significantly higher BMI
TABLE 3
Odds Ratios* (ORs) for HADS† Anxiety and Depression Caseness‡ in Overtime and Regular Workers in the Hordaland
Health Study§
Men Women
HADS-A HADS-D HADS-A HADS-D
No. of work hr/wk
Reference group㛳1.00 1.00 1.00 1.00
41–100 1.35 (1.13–1.61) 1.42 (1.16 –1.74) 1.44 (1.06–1.95) 1.61 (1.06–2.45)
41– 48 0.94 (0.70–1.25) 1.31 (0.97–1.77)
49 –100 1.67 (1.36 –2.06) 1.50 (1.17–1.93)
Major occupational groups
0 –3 1.00 1.00 1.00 1.00
4 –5 1.07 (0.86 –1.34) 1.31 (1.00–1.71) 1.01 (0.85–1.19) 1.18 (0.91–1.52)
6 –9 1.19 (1.01–1.39) 1.76 (1.46 –2.11) 1.11 (0.84 –1.46) 1.72 (1.18 –2.50)
Level of physical activity at work
Mainly sedentary work 1.00 1.00 1.00 1.00
Much walking ⫾much lifting 1.06 (0.92–1.24) 1.17 (0.98 –1.40) 1.01 (0.89–1.15) 1.04 (0.86–1.25)
Heavy manual labor 1.25 (0.96 –1.65) 1.49 (1.10 –2.02) 1.32 (0.65–2.69) 1.63 (0.64 – 4.18)
Shiftwork, night work or duties (yes) 1.21 (1.03–1.43) 1.20 (0.99 –1.46) 1.15 (0.96–1.39) 1.18 (0.90 –1.55)
Level of education
Less than A-levels/high school 1.12 (0.96 –1.30) 1.41 (1.17–1.69) 1.00 (0.84 –1.18) 1.22 (0.94 –1.56)
(Equivalent to) A-levels/high school 1.02 (0.79 –1.33) 1.15 (0.84 –1.58) 1.24 (0.97–1.60) 1.29 (0.88 –1.89)
College/university 1.00 1.00 1.00 1.00
Annual household income in NOK¶
⬍200.000 2.39 (1.71–3.33) 3.43 (2.35– 4.98) 1.74 (1.34 –2.25) 2.87 (1.96 – 4.20)
ⱖ200.000 and ⬍500.000 1.29 (1.08 –1.53) 1.65 (1.33–2.05) 1.20 (0.99 –1.44) 1.62 (1.18 –2.21)
ⱖ500.000 1.00 1.00 1.00 1.00
*Only unadjusted ORs are presented since adjustment for possible confounders did not give (statistically significant) different ORs. See
statistics for details about the adjustment procedures.
†Hospital Anxiety and Depression Scale; HADS-A: anxiety score, HADS-D: depression score.
‡Caseness: “Possible” cases of anxiety and depression (HADS-A and HADS-D scores ⱖ8, respectively).
§Number of workers in the groups: Reference group: men: n⫽5113, women: n⫽3979. All overtime: men: n⫽1099, women: n⫽251, least
overtime: n⫽458, most overtime: n⫽641.
㛳Reference group: Those working 35– 40 and 32–40 hour per week for men and women, respectively.
¶In 1999, NOK 200.000 and 500.000 were equivalent to EUR 24,067 and 60,168, respectively.
664 Working Overtime is Associated With Anxiety and Depression •Kleppa et al
compared with the reference group.
These findings support the theory
that the effect of long working hours
on mental health could be mediated
by poor lifestyle habits.
Physiological recovery mecha-
nism: Because of overtime work,
time available for recovery is re-
duced, potentially causing the indi-
vidual to be overtired mentally and
physically. It has been shown that
there is a negative association be-
tween number of hours of sleep dur-
ing weekdays and extended work
hours.
18
Our findings that a high
proportion of men working most
overtime reported heavy manual la-
bor and that overtime workers of
both genders more often worked
shifts than the reference group, may
indicate that reduced physiological
recovery is part of the causal path-
way. In a cross-sectional study
Nishikitani et al
12
found that work-
ing overtime was associated with
increased Hamilton Depression
Scale scores in a univariate analysis,
but not in multiple regression models
after controlling for sleep duration
and a job strain index based on the
Job Content Questionnaire.
Sanne et al
5
found that HADS levels
showed an inverse association with
skill levels. Low skill level jobs often
involve more heavy physical labor than
occupations with higher skill levels.
Fig. 2. Associations of hospital anxiety and depression scale (HADS) caseness (odds ratios with 95% confidence intervals) and working hours
in the Hordaland Health Study. x axis: number of working hours (2 to 100) per week. y axis: odds ratios with 95% confidence intervals. Anxiety
caseness: HADS anxiety score ⱖ8; depression caseness: HADS depression score ⱖ8.
JOEM •Volume 50, Number 6, June 2008 665
According to Spurgeon et al, “it is
arguable that the relation between
hours at work and ill health is medi-
ated by stress, in that long hours act
directly as a stressor, in increasing
the demands on a person who at-
tempts to maintain performance lev-
els in the face of increasing fatigue,
and indirectly by increasing the time
that a worker is exposed to other
sources of workplace stress.”
2
Long
work hours are likely to coincide
with high job demands and work
overload, which constitute crucial
factors in all the three leading stress
and burnout theories, namely The
Demand-Control model,
16
Maslach
et al’s comprehensive “Person within
context burnout model”
21
and The
Effort-Reward Imbalance Model.
22
Ezoe et al
19
found that mental
health status among persons working
overtime may be better among male
and worse among female workers.
This may be caused by the “double
load” that many women experience
(working both outside of and at
home). However, we were not able
to confirm these findings in the con-
text of our study.
Long work hours also reduce the
time left for family and social activ-
ities. The impact of overtime work
on mental health may possibly be
mediated by reduced quantity of im-
portant relationships.
Conclusion
In the Hordaland Health Study,
working overtime was associated
with increased levels of anxiety and
depression, and findings suggested a
dose-response relationship between
work hours and anxiety or depres-
sion scores. We also found that the
men reporting most overtime had a
significantly lower level of educa-
tion, more heavy manual labor,
worked more shifts, and were more
likely to have a low income com-
pared with the group working mod-
erate overtime.
Our finding that men working 49
to 100 hours per week had the high-
est levels of anxiety and depression
lends support to The European Com-
munity Directive on Working Time
which states that workers can refuse
to work more than 48 hours per
week. However, also a moderate
amount of overtime seems to be as-
sociated with an increased risk of
mental distress. The study results do
not unambiguously point toward a
specific causal hypothesis for this
increased risk.
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