Familial clustering in burnout: a twin-family study
C. M. MIDDELDORP*, J. H. STUBBE, D. C. CATH AND D. I. BOOMSMA
Department of Biological Psychology, Vrije Universiteit Amsterdam; Department of Psychiatry,
Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
Background. Research on risk factors for burnout has mainly focused on circumstances at work
and on personal characteristics. The aim of this study was to investigate whether burnout clusters
within families and, if so, whether this is due to genetic influences or to environmental factors
shared by family members. Finally, we tried to identify specific risk factors for burnout.
Method. In 2707 twins, 736 of their siblings and 575 of their spouses from a population-based twin-
family sample, burnout was measured using a self-report questionnaire. Correlations in burnout
scores were obtained for monozygotic and dizygotic twin pairs and sibling pairs conditional on
the pairs’ sex. Correlations for twins and their spouses were derived conditional on the length of the
Results. In the final model, correlations of the monozygotic and dizygotic twin pairs and sibling
pairs were significantly different from zero, but not significantly different from each other. The
correlation was estimated at 0.22. The correlation between spouses was also significant. This was
mainly due to the group with a relationship longer than 5 years in which the correlation was 0.24.
Burnout scores were higher in subjects whose parents had a high level of education.
Conclusions. There is familial clustering for burnout due to environmental factors shared by family
members, explaining 22% of the variance. Genetic factors do not seem to be of importance. The
significant correlation between spouses supports the conclusion that common environment plays
a role in burnout. A high parental education is one of the familial risk factors.
Burnout encompasses a work-related syndrome,
which is defined by three dimensions: an over-
whelming exhaustion, feelings of cynicism and
detachment from the job, and a sense of inef-
fectiveness and lack of accomplishment at work
(Maslach et al. 2001). Emotional exhaustion is
regarded as the key dimension of the syndrome,
and refers to feelings of being overextended and
depleted of one’s emotional and physical re-
sources (Maslach et al. 2001). There has been
considerable debate whether burnout is a dis-
tinct entity from depression. However, most
research indicates that depression and burnout
are not identical, although their symptoms are
positively related (Leiter & Durup, 1994; Glass
& Mcknight, 1996; Brenninkmeyer et al. 2001).
Burnout is a common problem. A study per-
formed in the Dutch general population re-
vealed, for example, that 10% of the people
participating in labour had symptoms of burn-
out (CBS, 1997).
Research on risk factors (for a review see
Schaufeli & Enzmann, 1998) indicated that
several job characteristics, such as experienced
workload and time pressure, role conflict and
role ambiguity, lack of social support at work,
lack of feedback, little participation in decision
making and lack of autonomy, are related to
teristics are linked to burnout, e.g. high levels of
neuroticism, an avoidant coping style and high
levels of type A behaviour (competition, time-
pressured lifestyle, hostility, and an excessive
need for control). Age has also been consistently
* Address for correspondence: Dr Christel Middeldorp, Vrije
Universiteit Amsterdam, Department of Biological Psychology, Van
der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands.
Psychological Medicine, 2005, 35, 113–120.
f 2004 Cambridge University Press
Printed in the United Kingdom
related to burnout. Among younger employees
the level of burnout is reported to be higher than
among those aged between 30 and 40 years. This
could be a result of survival bias, i.e. those who
burn out early in their careers are likely to quit
their jobs, leaving behind the survivors who
consequently exhibit lower levels of burnout.
Data on the effect of gender are contradictory.
Some studies show that burnout occurs more
often in women than in men, some show the
opposite and others find no overall differences.
Most research suggests that characteristics of
the work environment, particularly job stressors
such as workload, work pressure, etc., are more
strongly related to burnout than are personality
Schaufeli & Enzmann, 1998). This is confirmed
by a recent study among Dutch medical special-
ists which revealed that the organizational fac-
tors are more important in managing stress than
the personal factors (Visser et al. 2003).
So far, to our knowledge, no studies have in-
vestigated whether burnout clusters in families.
In general, familial clustering can be due to
shared genetic or common environmental fac-
tors. When familial clustering is absent, unique
environmental factors are primarily important.
Twin-family studies provide a good method to
estimate the influence of genes, common en-
vironment and unique environment on individ-
ual differences in behavioural and other traits
(Boomsma et al. 2002a). These studies make use
of the fact that monozygotic (MZ) twin pairs
share all (or nearly all) of their genes whereas
dizygotic (DZ) twin pairs share on average half
of their segregating genes. Consequently, if
MZ twin pairs are more similar for a trait than
DZ twin pairs, this suggests that genetic factors
influence this trait. If, on the other hand, MZ
twin pairs and DZ twin pairs show the same
tal factors, shared by family members, probably
play a role. The differences within MZ twin
pairs are explained by unique environmental
factors. Siblings, like DZ twin pairs, share on
average half of their segregating genes. But
twins and siblings may differ in the amount of
environment they share. For example, prenatal
conditions are different for singletons than for
twins and twins grow up together with someone
of their own age. Consequently, DZ twin pairs
are the perfect controls for MZ twin pairs.
Additional information on the similarity be-
tween siblings increases the power of a study
to detect effects of common environment (Post-
huma & Boomsma, 2000). Finally, by including
the spouses of twins in the sample, assortative
mating can be studied. Similarities between
spouses can develop during the relationship; it
is then a consequence of shared environment.
It is also possible that similarities already existed
at the beginning of the relationship. Therefore,
spouses might have chosen each other based on
No twin or family studies have investigated
whether burnout clusters in families, but there
is a wealth of twin studies on related conditions
and traits. Job satisfaction, which shares 20%
of its variance with burnout (Schaufeli &
Enzmann, 1998), has been studied in both US
twins reared apart and US twins reared together
(Arvey et al. 1989, 1994). Job satisfaction clus-
ters in families, but unique environmental fac-
tors explain most of the variance (around 70%).
Familial clustering in job satisfaction is a result
of genetic factors only.
sion of emotional exhaustion in burnout, but
does not require that it is work related. Twin
studies on symptoms of fatigue have shown
that familial clustering is present, but unique
environmental factors play a significant role
too, explaining between 50% and 80% of the
variance (Hickie et al. 1999a,b, 2001; Buchwald
et al. 2001; Sullivan et al. 2003). Regarding
causes for familial clustering, results differ
between studies. Results of the volunteer
Australian Twin Registry have indicated that
familial clustering for fatigue is due to genetic
factors only (Hickie et al. 1999a,b, 2001),
whereas in a US sample of twins partly recruited
from patients’ support groups, both genetic
and family environmental factors are causes
for familial clustering (Buchwald et al. 2001).
Finally, in a community sample of US twins
(the Mid-Atlantic Twin Registry, formerly
known as the Virginia Twin Registry) familial
clustering was a result of common environmen-
tal factors in males, while in females genetic
factors explained familial clustering (Sullivan
et al. 2003).
With respect to personality characteristics
related to burnout, the influences of genetic
and environmental factors have been studied
114C. M. Middeldorp et al.
extensively, especially for neuroticism. Reviews
of several population-based twin studies (Eaves
et al. 1989; Sherman et al. 1997; Lake et al.
2000) have concluded that familial clustering
is present in neuroticism as a result of genetic
factors only. Neuroticism is further influenced
by unique environmental factors. The same
seems to account for type A behaviour, although
this trait has been studied less extensively
(Pedersen et al. 1989; Sims et al. 1991; Duffy
et al. 1994; Sluyter et al. 2000). Regarding
avoidant coping style, results are less straight-
forward. One twin study assessed coping with
14 items chosen from the Ways of Coping
checklist. In a factor analysis, four of these
14 items were found to load on a factor called
‘denial’. Twin resemblance for this factor was
fully explained by common environmental
factors (Kendler et al. 1991). In another twin
study no such factor appeared from the factor
analysis (Busjahn et al. 1999). The results of
the analysis of the individual items of the ques-
tionnaire were also published. Items compar-
able with the items loading on ‘denial’ in the
paper of Kendler et al. (1991) were ‘Play down’,
‘Distraction from situation’, ‘Avoidance’ and
‘Flight tendency’. Twin resemblance for ‘Play
down’ and ‘Flight tendency’ was explained by
genetic factors, for ‘Distraction from situation’
by common environmental factors and for
‘Avoidance’ by both genetic and common en-
vironmental factors(Busjahnetal.1999). Again,
unique environmental factors were also found
to be important in avoidant coping style, ex-
plaining 50–90% of the variance (Kendler et al.
1991; Busjahn et al. 1999).
The aim of the current study was to inves-
tigate in males and females whether familial
clustering is present in burnout and, if so,
whether this is due to genetic or common en-
vironmental factors. The results of the twin
studies on job satisfaction, chronic fatigue and
on the personality characteristics related to
burnout lead to the expectation that burnout
will cluster in families mainly as a result of
genetic factors. However, since studies on the
risk factors for burnout have found that work
characteristics are more important than per-
sonal factors, unique environmental factors
will probably explain most of the variance. A
self-report questionnaire on burnout was used
that was completed by MZ twins, DZ twins,
their siblings and their spouses. Correlations
for the burnout scores were calculated between
MZ twin pairs, DZ twin pairs, sibling pairs and
between twins and their spouses. As pointed out
above, by comparing these correlations between
the different groups the proportion of influence
of genetic, common environmental and unique
environmental factors can be estimated for
males and females. To investigate whether as-
sortative mating is important, correlations were
calculated for three groups of twins and their
spouses conditional onthelengthoftherelation-
ship. Finally, taking into account the results of
these analyses, we tried to identify specific risk
factors for burnout.
This study is part of a longitudinal question-
naire study of the Netherlands Twin Register
(NTR) that has assessed families with ado-
lescent and young adult twins roughly every
rates are described in detail in (Boomsma et al.
2002b). For this paper, data were used from
the survey in 2000, which included several items
assessing burnout. Twins and their siblings were
requested to complete the survey. Spouses of
twins aged between 25 and 30 years were also
asked to participate. Mean duration of the re-
lationship of twins and spouses was 6.5 years
with a maximum of 16 years. The survey was
completed by 6701 subjects (excluding half sibs,
adoptive sibs and triplets). In the majority of
the twin pairs zygosity was determined from
questions about physical similarity and con-
fusion of the twins by family members, friends
and strangers. On 804 same-sex twin pairs infor-
mation on their zygosity was available from
DNA polymorphisms. The agreement between
zygosity diagnoses from the questionnaire and
DNA data was 98%.
Since burnout is a work-related syndrome,
subjects younger than 18 years or older than
65 years of age as well as subjects who were
tionnaire, were excluded from the study. Table 1
summarizes the number of subjects per inclusion
criterion. It can be seen that from the population
between 18 and 65 years of age, around 70% of
the subjects were employed. This percentage
Familial clustering in burnout 115
was higher than in the general population (CBS,
1997), probably because this was a relatively
young sample. In the group of people partici-
pating in labour, more men work full time and
more women work part-time. This is compar-
able with the general population (CBS, 1997).
Of the working people, 290 subjects were ex-
cluded, because they did not complete all the
questions about burnout. One sibling per family
was included, i.e. the sibling who was closest
in age to the twin pair. This led to the exclusion
of 202 siblings. Finally, 4018 subjects from 2328
families were included in the analysis.
Burnout was measured by a Dutch version of
the emotional exhaustion subscale of the
Maslach Burnout Inventory – General Survey
(Schaufeli et al. 1996). This questionnaire was
chosen, because it was also used in the study in
the Dutch general population (CBS, 1997). The
subscale consists of five items with an answer
range between 1 and 7 (never, a few times a year,
monthly, a few times a month, every week, a
few times a week, every day). The 5 items can
be summarized as (1) emotionally exhausted
because of work, (2) feeling empty after work,
(3) feeling tired in the morning when confronted
with work, (4) completely exhausted because of
work, (5) feeling worn out. Cronbach’s alpha
was 0.87 in our sample. The total score of the
five items was used for the analysis. The scores
were not normally distributed (skewness 2.0,
kurtosis 4.4). Therefore, correlations were cal-
culated for the log-transformed total burnout
score. This led to an improvement of the skew-
ness and kurtosis to 0.8 and 0.1 respectively.
Statistical analyses were performed with the
software programme Mx, modelling the depen-
dency that exists between measures of pairs of
relatives (Neale et al. 1999). Families may have
different numbers of observations within the
family, e.g. families with one participating twin
and one sibling, families with two participating
twins without sibling. To use all data, analyses
were performed on raw data using the raw like-
lihood method. To test whether means and
correlations were significantly different between
the groups of male and female twins, siblings
and spouses, the likelihood of the model in
which all parameters were estimated was com-
pared to the likelihood of the model in which
the parameters were constrained to be equal in
different groups. Twice the difference between
the log-likelihood of two models is distributed
asymptotically as x2. The degrees of freedom
(df ) for these tests are equal to the difference
in parameters being estimated. Utilizing the
principle of parsimony, the most restrictive
model was accepted as the best-fitting one in
case the difference between a nested and a more
comprehensive model was not significant (Neale
& Cardon, 1992).
To investigate assortative mating, the total
group of twins and their spouses was divided
in three groups according to the length of the
relationship: shorter than 5years, between 5 and
10 years and more than 10 years. Correlations
between burnout scores of spouses were calcu-
lated for the separate groups.
Table 1.Numbers of subjects per inclusion criterion
Male twins Female twins Male sibsFemale sibs Male spouses Female spouses
Total population15023046585 863442263
All subjects between 18 and 65 years
All employed subjects
(% full time/% part-time)*
All burnout questions completed
* Full time is defined as working more than 32 hours per week.
Table 2.Average age (years) and total
116C. M. Middeldorp et al.
Table 2 shows the average ages and total burn-
out scores in male and female twins, siblings and
spouses. Total burnout scores were not signifi-
cantly different between the groups. Keeping
in mind that the total burnout score ranges from
7–35 it is obvious that most subjects scored low.
Scores were comparable with Dutch general
population-based data (CBS, 1997).
Table 3 shows the correlations and 95%
confidence intervals for the full model, in which
all correlations are estimated without con-
straints, and for the final model for all twin
and sibling pairs: monozygotic male twin pairs
(MZM), dizygotic male twin pairs (DZM),
female twin pairs (DZF), dizygotic twin pairs
of opposite sex (DOS), brothers (SibMM),
sisters (SibFF), siblings of opposite sex (SibOS).
All these correlations could be constrained to
be equal. Table 4 shows the statistics of this
procedure. The significant correlation indicates
that familial clustering is present. Since the
correlations between MZ and DZ twin pairs
were not significantly different, familial cluster-
ing is due to common environmental factors
only, explaining 22% of the variance. Unique
environmental factors explain the remaining
78% of the variance.
Table 5 shows the correlations between twins
and their spouses for the total population and
after division into three groups conditional on
the length of relationship: shorter than 5 years,
between 5 and 10 years and more than 10 years
(maximum duration is 16 years). The correlation
in the total group was significantly different
from zero. The analysis of the three groups
revealed that this significant correlation is
due to the pairs of spouses with a relationship
over 5 years since the correlation of the pairs
with a relationship shorter than 5 years could
be constrained to zero (x2=1.427, 1 df). The
correlations of the other two groups were
Table 3. Number of family members and correlations between twin pairs and sibling pairs
MZMDZMMZF DZF DOSSibMM*SibFF* SibOS*
No. individuals in pairs
No. twins or siblings from incomplete pairs#
Correlations estimated in full model
CIs for full model
Correlations in constrained model
MZM, Monozygotic males; DZM, dizygotic males; MZF, monozygotic females; DZF, dizygotic females; DOS, dizygotic twins of opposite
sex; SibMM, brothers; SibFF, sisters; SibOS, sibs of opposite sex; CI, 95% confidence interval.
* Two values are given for the number of individuals in pairs, because siblings can form two pairs: a sib with twin 1 and a sib with twin 2.
# Incomplete pairs arise due to (1) subjects who did not participate in the survey (2) subjects who did not complete the burnout question-
naire (e.g. because they were unemployed).
Table 4. Likelihood of the different models
for the twin and sibling pairs
(1) Full model
(7) rSame sex twins and sibs=
30246.336 2 4.402
See Table 3 for explanation of the abbreviations.
Table 5. Spouse correlations
Length of relationship
No. individuals in pairs*
No. spouses from
CIs for full model
* The length of the relationship was unknown in 18 individuals.
Familial clustering in burnout117
significantly different from zero (x2=17.396, 2
df). They could be constrained to be equal (x2=
0.330, 1 df). This again suggests an influence of
To make sure that the influence of common
environment was not an effect of twins and
siblings having (nearly) the same age, a linear
regression analysis was performed with age and
total burnout score. Only in females was there
a significant negative relation (p<0.001), but
this explained only 0.7% of the variance. Conse-
quently, age cannot be responsible for the total
influence of the common environment, which
explains 22% of the variance. However, it is
interesting that this apparent age effect is prob-
ably due to the fact that women who work part-
time are, on average, older and have lower
burnout scores (Table 6). In males this effect
is absent, since only a minority of them work
part-time whatever their age.
To identify specific risk factors for burnout,
a univariate analysis of variance was performed
with items of the questionnaire from the year
2000 that assessed environmental factors shared
by family members, i.e. religious upbringing
and education of the parents. Burnout scores
were significantly higher in subjects with a
highly educated father or mother (p<0.001 for
both items). No differences were found in burn-
out scores between subjects with or without a
religious upbringing (p=0.11).
The results indicate that familial clustering
is present in burnout. This is due to common
environmental factors, since the correlations
of all pairs of relatives are significant and
equal. Furthermore, it is apparent that unique
environmental factors are most important
in the symptoms of burnout, explaining 78%
of the variance. These results are the same for
males and females. The significant spouse
correlation supports the finding that common
environment is of importance in burnout;
especially since the partner correlation tends to
increase with the length of the relationship.
Age cannot account for the effect of common
environment. A possible common environmen-
tal risk factor is a high level of education of the
A limitation of this study and of all other
studies on symptoms of burnout is that subjects
need to be working to complete the question-
naire. This means that if subjects do not work
any more, because they suffer from burnout,
they are not included in the study. In our sample
with regard to the males this does not seem to be
a problem (Table 1). The majority work full
time and most subjects who do not work are
students. With respect to women, a survival bias
might have influenced our results. Around 40%
are working part-time or engaged in house-
keeping. Possibly these women choose not to
work full time because of symptoms of burnout.
However, the results of a study on non-response
bias in the same population of twins and siblings
suggested that the data collected on health,
personality and lifestyle are relatively unbiased
(Vink et al. in press). The analyses in this study
were based on the idea that when the variable of
interest has a familial component, data from
respondents can be used as proxy for the data
from their non-responding family members.
Therefore, mean burnout scores of participants
from families with a high response rate (more
than 80% of the family members participated)
were compared with mean burnout scores of
participants from families with a low response
rate (less than 80% of the family members par-
ticipated). No significant difference in burnout
scores were found.
It is consistent with earlier studies, which have
found that work characteristics are more related
to burnout than personal factors, that unique
environmental factors are most important. It
follows that circumstances at work should re-
main a focus of research. However, caution is
and females working full time or part-time
Age and burnout scores for males
12 and 32 hours
1495 31.2 9.51308 28.0 10.3
90 30.99.7842 33.29.2
17 25.26.8 111 34.97.3
* Working hours were unknown for 58 males and 97 females.
118C. M. Middeldorp et al.
needed in defining a risk factor as part of the
unique environment. Work values, for example,
are partly influenced by genetic factors (Arvey
et al. 1994). This signifies that the organization
in which a subject is employed cannot be con-
sidered as a pure environmental factor. This
problem can be tackled through comparing
levels of burnout of MZ twins who work in dif-
ferent environments. Based on earlier results of
twin studies on job satisfaction, chronic fatigue
and personality characteristics related to burn-
out, we predicted that burnout would cluster in
families mainly as a result of genetic factors.
Hence, it was rather unexpected that familial
clustering in burnout is due to common en-
vironmental factors and not to genetic factors,
particularly because a recently published review
(Bouchard & McGue, 2003) shows that most
lifestyle and personality traits cluster in families
because of genetic factors. However, all results
of this study support the conclusion that com-
mon environmental factors are important in
burnout. Two complementary explanations
could be offered for these seemingly divergent
findings. Overlapping unique environmental
factors could underlie the relationship between
burnout and the other traits, since unique
environmental factors explain half or more of
the variance in all these traits. To a lesser extent,
this could also be the case for common environ-
mental factors, since familial clustering in both
an avoidant coping style and in fatigue has been
found to be (partly) due to common environ-
mental factors. Another explanation for the
apparent absence of genetic influence on symp-
toms of burnout could be gene–unique environ-
ment interaction. In twin studies the effect of an
interaction between genes and unique environ-
ment cannot be distinguished from the effect of
unique environmental factors alone, since both
will lead to differences between MZ twins. There
is some support for the hypothesis that gene–
environment interaction influences burnout.
Burnout scores are more strongly influenced by
job stressors in individuals who score high on
negative affectivity, a symptom highly compar-
able with neuroticism, than in individuals who
score low on negative affectivity (Houkes et al.
2003). This signifies that a trait, which is partly
influenced by genetic factors, interacts with job
stressors, which are possibly unique environ-
mental factors. Although speculative, it can be
hypothesized that this might be a result of an
interaction between genes leading to negative
affectivity and unique environmental factors
leading to burnout.
Common environmental factors within the
family have rarely been a focus of research on
risk factors for burnout. There are a few articles
on the effect of family environment on work
attitudes. Barling et al. (1998) have investigated
the effects of parents’ job insecurity on work
beliefs and attitudes of male and female under-
graduate students. In the best-fitting model
children who watch their parents experiencing
layoffs and insecurity perceive this insecurity
and develop negative work beliefs that predict
their work-related attitudes (Barling et al. 1998).
Loughlin & Barling (2001) describe how con-
temporary young workers in the US might be
influenced by having seen their parents and
others around them being ‘rightsized’ or ‘down-
sized’ or otherwise dismissed from their jobs
during the 1980s and 1990s. They hypothesize
that this new cohort of young workers are less
willing to make sacrifices for the sake of their
jobs (Loughlin & Barling, 2001). Since our study
suggests that familial circumstances, e.g. high
level of education of the parents, can lead to
vulnerability forburnout, futureresearch should
pay more attention to the influence of the work
characteristics and attitudes of the parents (e.g.
profession, level of ambition, experiences of
The influence of the environment shared by
spouses on functioning at work has been studied
much more, but is still not well understood
that spouse disagreement, other family criti-
cism/burden and spousal affective support are
related with subjective functioning at work. No
studies have investigated the effect of having a
partner with symptoms of burnout. Regarding
the significant correlation in burnout scores
between spouses, it might be useful to study
couples to find out which circumstances make
both of them vulnerable for burnout, e.g. dual
earner families with children, caregiving needs
of parents or having a partner with symptoms of
To summarize, our major result is that burn-
out clusters in families as a result of environ-
mental factors shared by family members. This
should be a focus of future research.
Familial clustering in burnout119
This research was supported by ZonMW (940-
37-024, 904-61-193, 985-10-002).
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