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Post-traumatic stress disorder as a consequence of bullying at work and
at school. A literature review and meta-analysis
Morten Birkeland Nielsen
a,b,
⁎
,ToneTangen
c
, Thormod Idsoe
d,e
, Stig Berge Matthiesen
f,b
,NilsMagerøy
g
a
National Institute of Occupational Health, Oslo, Norway
b
Department of Psychosocial Science, University of Bergen, Bergen, Norway
c
Clinical Institute 1, Section of Psychiatry, University of Bergen, Haukeland University Hospital, Bergen, Norway
d
Norwegian Center for Child Behavioral Development, Oslo, Norway
e
Norwegian Centre for Learning Environment and Behavioural Research in Education, Stavanger, Norway
f
Department of Leadership and Organizational Behavior, BI Norwegian Business School, Oslo, Norway
g
Department of Occupational Medicine, Haukeland University Hospital, Bergen, Norway
abstractarticle info
Article history:
Received 26 February 2014
Received in revised form 19 December 2014
Accepted 6 January 2015
Available online 13 January 2015
Keywords:
Bullying
Mobbing
Trauma
Stress
Meta-analysis
Bullying has been established as a prevalent traumatic stressor both in school and at workplaces. It has been
claimed that the mental and physical health problems found among bullied persons resembles the symptomatol-
ogy of Post Traumatic Stress Disorder (PTSD). Yet, it is still unclear whether bullying can be considered as a pre-
cursor to PTSD. Through a review and meta-analysis of the research literature on workplace- and school bullying,
the aims of this study were to determine: 1) the magnitude of the association between bullying and symptoms of
PTSD, and 2) whether the clinical diagnosis of PTSD applies to the consequences of bullying. Altogether 29 rele-
vant studies were identified. All had cross-sectional research designs. At an average, 57% of victims reported
symptoms of PTSD above thresholds for caseness. A correlation of .42 (95% CI: .36–.48; p b .001) was found be-
tween bullying and an overall symptom -score of PTSD. Correlations between bullying and specificPTSD-
symptoms were in the same range. Equally strong associations were found among children and ad ults. Two
out of the three identified clinical diagnosis studies suggested that bullying is associated with the PTSD-
diagnosis. Due to a lack of longitudinal research and structural clinical interview studies, existing literature pro-
vides no absolute evidence for or against bullying as a causal precursor of PTSD.
© 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Contents
1. Introduction............................................................... 18
1.1. Background............................................................ 18
1.2. Aimsofthestudyandresearchquestions............................................... 19
2. Methods................................................................. 19
2.1. Materialandprocedure....................................................... 19
2.2. Meta-analyticapproach....................................................... 19
3. Results ................................................................. 19
3.1. FrequencyofPTSD-symptoms.................................................... 19
3.2. ReviewofclinicalstudiesoftherelationshipbetweenbullyingatworkandPTSD-diagnosis........................ 20
3.3. RelationshipbetweenbullyingandPTSD-symptoms.......................................... 20
4. Discussion................................................................ 21
4.1. Methodologicalconsiderations................................................... 22
4.2. Conclusionandsuggestionsforfutureresearch............................................ 22
Acknowledgement............................................................... 23
References.................................................................. 23
Aggression and Violent Behavior 21 (2015) 17–24
⁎ Corresponding author at: National Institute of Occupational Health; PB 8149 Dep; 0033 Oslo; Norway. Tel.: +47 23195264.
E-mail address: morten.nielsen@stami.no (M.B. Nielsen).
http://dx.doi.org/10.1016/j.avb.2015.01.001
1359-1789/© 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Contents lists available at ScienceDirect
Aggression and Violent Behavior
1. Introduction
With an estimated prevalence rate of 32% in schools (Solberg &
Olweus, 2003)and15%inworkplaces(Nielsen, Matthiesen, &
Einarsen, 2010), bullying is a significant social stressor for many adults
and c hildren. The concept of bullying refers to a long-lasting and
systematic form of interpersonal aggression where an individual is
persistently and over time exposed to negative actions from superiors,
co-workers or other students, and where the target finds it difficult to
defend her-/himself against these actions (Einarsen & Skogstad, 1996;
Olweus, 1993). Following this definition, workplace- and school
bullying can be described as a two-step process. The first step includes
exposure to systematic bullying behavior over time, whereas the second
step comprises a subjective interpretation of being victimized by these
bullying behaviors (Nielsen & Knardahl, in press). There is no definitive
list of bullying behavior, but most often bullying involves repeated
exposure to aggression in the form of verbal hostility, teasing,
badgering, being made the laughing stock of the department/classroom,
and social exclusion (Einarsen, 2000; Solberg & Olweus, 2003).
While there are some differences in the phenomenology of bullying
among children and ad ults, there are also many similarities and
continuities (Monks et al., 2009; Smith, 1997). For instance, the most
commonly used definitions of school- and workpl ace bullying are
comparable in that they emphasize persistent and repeated negative
actions which the target perceive and interpret as intended to intimi-
date or hurt and a systematic abuse of power as the main definitional
characteristics (Smith, Singer, Hoel, & Cooper, 2003). Furthermore, a
consistent body of evidence shows that persons who bul ly others at
school also are likely to bully as adults, a finding which indicates that
there are intergenerational continuities in bullying tendencies (Ttofi,
Farrington, & Losel, 2012). Similarly, retrospective research findings
show that victimization from bullying in school increases the risk of
being bullied in adult life (Smith et al., 2003). Finally, the predictors
and outcomes of bullying in school and at the workplace are similar or
overlapping (Smith et al., 2003). These similarities suggest that
school- and workplace bullying are strongly interrelated phenomena
and that it is meaningful to review findings from the two research fields
together.
In the research on psychological effects of bullying, both amon g
children and adults, exposure to systematic and long-lasting hostile
and abusive behavior at work has been asso ciated with a range of
negative health effects, including somatic as well as psychological
symptoms. Several studies have reported both cross-sectional and
long-term associations between bullying and symptoms of anxiety
and depression, sleeping problems, irritability, lack of concentration
and somatic complaints like muscle–skeletal pain, fatigue and gastroin-
testinal symptoms (Arseneault, Bowe s, & Shakoor, 2010; Bowling &
Beehr, 2006; Nielsen & Einarsen, 2012). Taken together, these health
problems resemble the symptomatology which characterizes post-
traumatic stress disorder (PTSD) and it has, therefore, been proposed
that exposure to bullying may lead to PTSD (Kreiner, Sulyok, &
Rothenhausler, 2008; Leymann & Gustafsson, 1996; Matthiesen &
Einarsen, 2004; Tehrani, 2004
). Yet, it is heavily debated whether the
PT
SD diagnosis can be applied to the health consequences of non-
physical forms of aggression such as bullying; and it remains unclear
whether bullying can be seen as a cause of post-traumatic stress
symptoms. Through a review and meta-analysis of the literature on
school- and workplace bullying, the present study makes a unique
contribution to the research field by being the first comprehensive
and exhaustive statistical synthesis and summary of the empirical
evidence regarding the impact of bullying on PTSD.
1.1. Background
PTSD is an anxiety disorder consisting of a constellation of three
distinct areas of symptoms (persistent re-experiencing the event,
avoidance of stimuli associated with the trauma, and persistent arous-
al), resulting from exposure to a traumatic event (American Psychiatric
Association, 2000). A PTSD diagnosis is warranted when at least one
symptom of re-experiencing the event, three symptoms of avoidance
and two hyper arousal symptoms are present for at least one month
to an extent that they cause clinically significant distress or impairment
in daily functioning.
When first formulated in 1980, the diagnosis of PTSD was not
regarded as relevant for children and adolescents; however, a develop-
mental perspective has gradually been introduced in the different
versions of the DSM. The symptoms of PTSD in children and adolescents
are almost isomorphic to the adult core criteria. However, encompassing
features specific to children, such as repetitive play and trauma specific
play reflecting reliving of the trauma, may be conveyed. Children may
have difficulties reporting diminished interest in significant activities
and constriction of affect (avoidance), and this may only be discovered
through careful evaluations with reports from parents, teachers and
other observers. Children may also exhibit physical symptoms such as
stomachaches and headaches (American Psychiatric Association, 2000;
Idsoe, Dyregrov, & Idsoe, 2012).
PTSD differs from other psychiatric diagnoses by its dependence on
two distinct processes: 1) The exposure to trauma, and 2) The develop-
ment of a specific pattern of symptoms in temporal or contextual relation
to the traumatic event. The diagnostic A-criterion specifies that the
individual must be sufficiently exposed to a qualifying traumatic event
to get a PTSD diagnosis. Specifical ly, the A-criterion states that a person
must be directly or indirectly exposed to death, threatened death, actual
or threatened serious injury, or actual or threatened sexual violence in
order to qualify for the PTSD-diagnosis (American Psychiatric Association,
2013). As bullying does not represent a single traumatizing event, but
rather a systematic and exposure to mainly non-physical aggression
over a prolonged time-period, it has been suggested that the PTSD-like
symptoms found among victims of bullying should rather be subsumed
under the diagnoses such as adjustment disorder, depressive disorder,
or anxiety, or simply distress that is not part of a defined psychiatric dis-
order. Yet, others argue that psychosocial events without immediate
physical injury should qualify for the diagnosis of PTSD (Rosen, Spitzer,
& McHugh, 2008), and the A-criterion has been altered in successive edi-
tions of Diagnostic and Statistical Manual of Mental Disorders (DSM). The
ongoing debate is both based on the differences in interpretation of the A
criterion as a qualifying stressor and on the developmen t PTSD (Brewin,
Lanius, Novac, Schnyder, & Galea, 2009; Kraemer, Wittmann, Jenewein,
Maier, & Schnyder, 2009; Rosen, Lilienfeld, Frueh, McHugh, & Spitzer,
2010). In DSM version IV, a subjective component was included in the
A-criterion and stated as “personal response of intensive fear, helpless-
ness or horror” (American Psychiatric Association, 2000).
Although exposure to bullying constitutes a systematic exposure to a
s
eries of negative events over a prolonged time period, rather than one
single traumatic event, it has been claimed that the distress many of the
victims experience equalizes the stress associated with trau matic
events (Matthiesen & Einarsen, 2004; Mikkelsen & Einarsen, 2002;
Tehrani, 2004). Building on Janoff-Bulman's (1992) theory of shattered
assumptions, it has been suggested that bullying is a traumatic event in
that prolonged exposure to the phenomenon shatters the target's most
basic cognitive schemes about the world, other people, and ourselves
(Mikkelsen & Einarsen, 2002). Insofar as stability is needed in conceptu-
al systems, abrupt changes in core schemas are deeply threatening and
may result in traumatization (Janoff-Bulman, 1992). Research supports
the notion of non-physical events as potential traumatizing. For
instance, in a study of post-traumatic symptoms in health workers, it
was found that respondents rated verbal aggression as having a larger
impac t on posttraumatic stress symptoms than phys ical aggression
(Walsh & Clarke, 2003). Verbal aggression was particularly associated
with intrusive recollections.
In addition to the problem of defining the level of trauma qualifying
for the diagnosis, th e link between stressor and symptoms raise
18 M.B. Nielsen et al. / Aggression and Violent Behavior 21 (2015) 17–24
problems with causality. Causality in psychiatry is complex and will in
many cases represent an oversimplification. In causality, one has to
take into consideration both pre-event factors for the individual, peri-
event factors related to the actual trauma, and post-event factors related
to the time after the trauma. Personality traits, like neuroticism, pre-
existing psychiatric disorders as anxiety and depression, lack of support
or experiencing other stressful life-events, are all risk factors for devel-
oping PTSD. Important factors related to the actual trauma may be
whether the stressful acute events were non-expected or predictable,
as well as whether the individual was able to cope with the situation.
Important post-event factors may be lack of support or physical injury
as a consequence of the event (Bisson, 2007; Keane, Marshall, & Taft,
2006). Hence, with regard to establishing a causal association between
bullying and PTSD, one has to consider both the effect of bullying on
post-traumatic stress over time, as well as ruling out the impact of
potential pre-, pe ri-, and post-event factors t hat may influence the
relationship.
1.2. Aims of the study and research questions
In order to add to the understanding of the relationship between
bullying and PTSD, the main objective of the current study was to eval-
uate, on the b asis of existing research, whether bullying at wor k or
school may lead to PTSD. By means of literature review and meta-
analysis of the existing research literature, the following two research
question will be investigated:
1) What is the magnitude of the association between bullying and symp-
toms of PTSD?
2) Does the diagnosis of PTSD apply to the health consequences found
among targets of bullying?
As discussed above, “the diagnosis of PTSD” and “symptoms of PTSD”
are used interchangeably in the literature on posttraumatic stress and
workplace bullying. In the present study, we separate between studies
where the focus has been the full PTSD-diagnosis and studies wher e
only post-traumatic stress symptoms (i.e., hyperarousal, intrusion, and
avoidance) have been assessed.
2. Methods
2.1. Material and procedure
To identify relevant studies, we followed the literature search
strategies proposed by Durlak and Lipsey (1991). Bullying, harassment,
mobbing, mistreatment, emotional abuse,andvictimization/victimization
are concepts that have been used to describe exposure to long-lasting
and systematic psychological and physical aggression (Einarsen, Hoel,
Zapf, & Cooper, 2011; Nielsen et al ., 2010; Zapf & Einarsen, 2005 ).
While there may be subtle theoretical differences between these
concepts, they are all in line with the definition of bullying presented
in the introduction of this article which highlighted duration, persisten-
cy, and power imbalance as the main definitional characteristics. The
above keywords were combined with post-traumatic stress, trau ma,
PTSD, PTS, and PTSS and entered in the PsychINFO, ISI Web of Science,
Science Direct, Pubmed, and Proquest databases. Internet searches via
www.google.com and Google Sc holar were also performed to find
other available articles. The search included studies published up to
October, 2014. Papers on related, but less persistent and long-lasting,
pheno
mena such as incivility, social undermining, general abuse, and
aggression were screened in order to reveal studies on the phenomenon
of workplace bullying being presented under different labels. Further,
the authors' personal collection of publications on bullying from around
1988 to the present was examined to find any missing publications. As a
final step, citations in the collected publications were inspected. The
study coding form was developed by following the guidelines presented
by Lipsey and Wilson (2001).
Only studies that used validated questionnaires to assess post-
traumatic stress were included in the review. To be included in the
meta-analytic part of the study, studies had to provide the zero-order
correlations between bullying and symptoms of post-traumatic stress,
or provide sufficient information for these correlations (effect sizes) to
be calculated. Studies that lacked this informa tion or reported effect
sizes that could not be transformed into correlations were excluded
from the meta-analyses. To avoid double-counting data, the sample in
a given study should not have been used in a previous study of those
included in our review.
2.2. Meta-analytic approach
For all studies, effect sizes were calculated by means of averaged
weighted correlations across samples. The Q statistic was used to assess
the heterogeneity of studies. A significant Q value rejects the null
hypothesis of homogeneity. An I
2
statistic was computed as an indicator
of heterogeneity in percentages. Increasing values show incre asing
heterogeneity, with values of 0% indicating no heterogeneity, 50% indi-
cating moderate heterogeneity, and 75% indicating high heterogeneity
(Higgins, Thompson, Deeks, & Altman, 2003). As considerable heteroge-
neity was expected between studies, we calculated the pooled mean
effect size using the random effects model. Random effects models are
recommended when accumulating data from a series where the effect
size is assumed to vary from one study to the next, and where it is
unlikely that studies are functionally equivalent (Borenstein, Hedges,
&Rothstein,2007). Furthermore, random effects models allow statisti-
cal inferences to be made regarding a population of studies beyond
those included in the meta-analysis (Berkeljon & Baldwin, 2009).
It is a potential shortcoming of meta-analyses that overall effect sizes
can be overestimated due to a publication bias in favor of significant
findings. To approach this so-called “file drawer problem” we calculated
the Fail-Safe N and Funnel plots. The Fail Safe N reflects the number of
studies reporting null results that would be required to reduce the over-
all effect to non-significance (Borenstein, Hedges, Higgins, & Rothstein,
2009). A funnel plot is a simple scatter plot of the effect estimates from
individual studies against a measure of each study's size or precision. In
the absence of publication bias, the studies will be distributed symmetri-
cally about the mean effect size. In the presence of publication bias the
studies are expected to follow the model with symmetry at the top, a
few studies missing in the middle, and more studies missing near the
bottom (Borenstein et al., 2009). Meta-analyses and analyses of publica-
tion bias were carried out using the Comprehensive Meta-Analysis
(version 2) software developed by Biostat (Borenstein, Hedges, Higgins,
&Rothstein,2005).
3. Results
The literature search yielded 29 relevant studies. Altogether 26
papers focused on the association between bullying and PTSD-
symptoms. Of these, seven described frequencies of symptoms and 18
provided the zero-order correlations between bullying and symptoms
of post-traumatic stress. In addition, one retrospective study showed
that recollections of being exposed bullying in childhood was associated
with symptoms of posttraumatic stress in adulthood (Murphy, Shevlin,
Armour, Elklit, & Christoffersen, 2014) For the association be tween
bullying and the formal diagnosis of PTSD as assessed by clinical
interview, only three studies were found. All three were based on
adult populations.
3.1. Frequency of PTSD-symptoms
An overview of studies which reported the frequency of PTSD-caseness
among victims of bullying is included in Table 1. After weighting rates on
the sample size of each study, an average of 57% (95% C.I. = 42–70) of
all victims had symptoms scores above thresholds for caseness.
19M.B. Nielsen et al. / Aggression and Violent Behavior 21 (2015) 17–24
3.2. Review of clinical studies of the relationship between bullying at work
and PTSD-diagnosis
In a Swedish study of 64 patients at a rehabilitation center for
victims who had experienced bullying at work, the symptoms of PTSD
were assessed by a structured psychiatric interview (Leymann &
Gustafsson, 1996). The patients were all chronic sufferers after long
term bullying. The majority of the patients were referred by social insur-
ance offices in Sweden, whereas a small number were directly referred
by the employer. The sample comprised 20 men and 44 women.
Patients were rated on several diffe rent catastroph ic diagnostic
instruments. Symptoms of posttraumatic stress were assessed with
the 15 items version of the Impact of Event Scale (Horowitz, Wilner, &
Alvarez, 1979) and the 10 ite m Post-tra umatic symptom scale
(Raphael, Lundin, & Weisaeth, 1989), The DSM-III-R diagnostic manual
was used as a diagnostic summary of the questionnaires. Totalinterview
time varied between four to 10 h. Of the 64 patients assessed, 59 (92%)
qualified for a diagnosis of PTSD.
In a German study by Kreiner et al., (2008) which included patients
from a psychiatric outpatient clinic open to the public, 20 persons who
had been severely bullied at work were interviewed with SCID-I which
is a validated structured clinical interview aiming at assessing diagnoses
according to DSM-IV. Of these patients, 11 (55%) qualified for the
diagnosis of PTSD.
In a single-case study from Italy (Signorelli, Costanzo, Cinconze, &
Concerto, 2013), the aim was to determine whether “post-traumatic
stress disorder” or “adjustment disorder” (AD) was the most appropriate
diagnosis for a victim of bullying. The case study is based on a 58-year-old
female nurse who, after a brilliant career, underwent bullying at the
workplace, and showed depression, anxiety, and sleep disorders that
required hospitalization and a substantial intervention. According to the
DSM-IV-TR criteria, a diagnosis of AD with anxiety and depressive
mood was made. The Structured Clinical Interview for DSM-IV Axis I
Disorders (SCID I) excluded any other Axis I Diagnosis, such as major
depressive disorder or anxiety disorders. The Clinician-Administered
PTSD Scale (CAPS) also excluded PTSD.
3.3. Relationship between bullying and PTSD-symptoms
The 19 studies that provided information on associations between
expos ure to workplace or school bullying and symptoms of post-
traumatic stress were included in the meta-analysis. An overview of
the included studies is provided in Table 2. One study included two
samples (Laschinger & Nosko, 2013). The total sample size for these
20 samples was 6378 respondents (range: 23 to 1010). Thirteen
samples were based on adult populations, whereas seven samples
employed children and adolescents in their samples. Of the included
studies of adults (K = 12; N = 4246), three originated from Norway,
whereas two originated from Italy, two from Lithuania, and two from
Denmark. The remaining studies were from Australia, Canada, and
Pakistan. The studies on children and adolescents (K = 7; N = 2132)
originated from USA (3), UK (2), Italy (1), and Norway (1). With the ex-
ception of one study which used the Work Harassment Scale developed
by Björkqvist, Österman, and Hjeltbäck (1994), all studies among adults
Table 1
Frequency of victims of bullying with Post Traumatic Stress Disorder symptoms above thresholds for caseness.
Sample Study N bullied Location Bullying measure PTSD-measure PTSD symptoms (%)
Adult Balducci, Alfano, and Fraccaroli (2009) 107 Italy Negative Acts Qustionnaire (NAQ) MMPI-II 52
Adult Matthiesen and Einarsen (2004) 102 Norway NAQ + Self-labeling PTSS-10 + IES-R 75
Adult Mikkelsen and Einarsen (2002) 118 Denmark NAQ + Self-labeling PDS 76
Adult Nielsen, Matthiesen, and Einarsen (2005) 199 Norway NAQ-R + Self-labeling IES-R 84
Adult Rodriguez-Munoz, Moreno-Jimenez, Vergel, and Garrosa (2010) 183 Spain Bullying at Work Questionnaire SIP 42.6
Adult Tehrani (2004) 165 UK Self-labeling IES-R 44
Children Idsoe et al. (2012) 450 Norway Roland & Idsoe's scale Cries-8 33.7
Children Mynard, Joseph, and Alexander (2000) 136 UK Victims scale IES-R 37
Total Average weighted rate 57
(95% C.I. = .42–.70)
Table 2
Overview of studies included in meta-analysis.
Sample Study N Location Bullying measure PTSD-measure Weighted correlation 95% C.I.
Adult Balducci et al. (2009) 107 Italy NAQ MMPI-II .22 .03–.39
Adult Balducci, Fraccaroli, and Schaufeli (2011) 609 Italy NAQ PCL-C .42 .35–.48
Adult Bond, Tuckey, and Dollard (2010) 139 Australia NAQ PPTSD-R .52 .39–.63
Adult Glasø et al. (2009) 72 Norway NAQ IES-R .39 .17–.57
Adult Høgh et al. (2012) 1010 Denmark NAQ IES-R .42 .37– .47
Adult Laschinger and Nosko (2013)
Sample 1
244 Canada NAQ PC-PTSD .55 .46–.63
Adult Laschinger and Nosko (2013)
Sample 2
631 Canada NAQ PC-PTSD .60 .55–.65
Adult Malik and Farooqi (2014) 300 Pakistan WHS PCL-C .49 .40–.57
Adult Malinauskiene and Jonutyte (2008) 370 Lithuania NAQ IES-R .34 .25–.43
Adult Malinauskiene and Bernotaite (2014) 323 Lithuania NAQ IES-R .50 .35–.62
Adult Matthiesen and Einarsen (2004) 102 Norway NAQ IES-R .37 .19–.53
Adult Mikkelsen and Einarsen (2002) 118 Denmark NAQ PDS .34 .17–.49
Adult Nielsen et al. (2008) 221 Norway NAQ IES-R .41 .29–.51
Children Beckerman and Auerbach (2014) 23 USA N/A PCL .70 .41–.86
Children Crosby, Oehler, and Capaccioli (2010) 244 USA SEQ-SR TSCC .66 .58–.73
Children Guzzo, Pace, Lo Cascio, Craparo, and Schimmenti (2014) 488 Italy Olweus TSCC .16 .07–.24
Children Idsoe et al. (2012) 936 Norway Roland & Idsoe's scale Cries-8 .34 .28–.40
Children Mynard et al. (2000) 136 UK Victims scale IES-R .24 .06–.41
Children Pessall (2001) 104 UK DIPC DTS .31 .13–.47
Children Storch and Esposito (2003) 201
USA SEQ TSCC .35 .22–.47
20 M.B. Nielsen et al. / Aggression and Violent Behavior 21 (2015) 17–24
used the Negative Acts Questionnaire (Einarsen, Hoel, & Notelaers,
2009) to measure exposure to workplace bullying. Different question-
naires, such as the f our item scale developed by Roland and Idsoe
(2001), were used in the studies of children.
Table 3 presents the main findings from the met a-analyses. After
weighting each correlation by sample size, an average correlation of
.42 (95% CI: 36–.48; p b .001) was established between exposure to bul-
lying and an overall symptom-score of PTSD. A significant Q-statistic
(Q = 148.93; df =19;p b .001) and an I
2
of 87.24 indicated high levels
of heterogeneity between the meta-analyzed studies. With a total of
5247 non-significant studies needed to reduce the overall effect to
non-significance, the fail-safe N estimates indicate that the effect size
observed in the present meta-analysis is likely to be robust (z =
31.81; p b .001). A funnel plot disclosed moderate asymmetry between
the individual effect sizes (see Fig. 1). Analyses of effect size among
children (r =.39;95%C.I.=.24–.52; p b .001 ) and adults (r = .44;
95% C.I. = .38–.50; p b . 001) indicated no significant differences in
average weighted correlations for the two groups (Q
between
=.42;
df =1;p N .05). This finding suggests that bullying has an equally strong
association with symptoms of p ost-traumatic stress among children
and adults. Still, the larger confidence interval among children indicates
alargervariationinfindings for this group compared to adults.
In order to investigate the relationship between exposure to bullying
and the individual symptoms of post-traumatic stress (i.e., avoidance,
intrusion, and hyp er-arousal), a meta-analysis was conducted on
studies which presented findings on the three distinct symptom scores.
In all, five studies reported findings on the relationship between
bullying and the PTSD symptoms that could be included in the meta-
analysis (Glasø, Nielsen, Einarsen, Haugland, & Matthiesen, 2009;
Høgh, Hansen, Mikkelsen, & Persson, 2012; Matthiesen & Ei narsen,
2004; Mikkelsen & Einarsen, 2002; Nielsen, Matthiesen, & Einarsen,
2008). The total sample size for these studies was 1501 respondents.
All studies were based on adult populations. An average correlation of
.37 (95% CI: .32–.43; p b .001) was established between exposure to bul-
lying and avoid ance, whereas a correlation of .39 (95% CI: .35–.46;
p b .001) was found b etween bullying and intrusion. The strongest
association was found between bullying and hyper arousal (r = . 41;
95% CI: .32–.43; p b .001). However, as indicated by the overlapping
confidence intervals, the differences between the symptoms scores
were not significant (Q = .58; df =2;p N .05).
4. Discussion
This review of the existing research literature on the relationship
between bullying and the diagnosis of PTSD, shows that bullying is
associated with symptoms of post-traumatic stress, but that there is a
shortage of clinical and prospective research on the association. With
regard to clinical assessments, only three studies were identified. The
number of participants in these studies was small and in two of the
studies patients were recruited from rehabilitation centers for victims
of long-term bullying. The degree of bullying and pre-,peri-, and post-
event factors were not very well described and this limits the generaliz-
ability of the results. While the results of the clinical assessments in two
of the clinical studies indicate an association between bullying at work
and diagnosis of PTSD, the single-case study by Signorelli et al. (2013)
found that PTSD was not an adequate diagno sis for the investigated
victim of bullying.
Our findings show that an average of 57% of victims of bullying
report symptom scores for PTSD above cut-off thresholds for caseness.
In comparison, the estimated lifetime prevalence of PTSD among adult
Americans is 7.8%.
1
This suggests that PTSD symptoms are overrepre-
sented among bullied persons. Further information about the associa-
tion between bully ing and posttraumatic stress was provided in the
meta-analytical part of this study in that exposure to bullying at work
and in school was fou nd to be signifi cantly associated with post-
traumatic stress symptoms. Following the recommendations of Cohen
(1988), the establ ished average correlation was moderate to stron g
(0.42). Compared to findings from previous meta-analysis on outcomes
of bullying, this association is stronger than correlations between bully-
ing at work and outcomes such as psychological distress, physical health
and well-being, general strain, and burnout (Hershcovis, 2011; Nielsen
&Einarsen,2012)
Looking at the association between th e t hree symptoms clusters
(B—intrusion, C—avoidance/numbing and D—hyper arousal) the
highest correlation was found for hyper arousal (0.41) while the corre-
lation for intrusion and avoidance was 0.37 and 0.39, respectively. The
differences in average scores between symptoms were not significantly
different. Earlier studies have found the avoidance/numbing symptoms
(cluster C) to be the strongest determinants of PTSD (Breslau,
Reboussin, Anthony, & Storr, 2005; Ehlers, Mayou, & Bryant, 1998)
and that meeting group C criteria after a traumatic event was associated
with functional impairment from post-traumatic symptoms (Breslau
et al., 2005). As described in the DSM-V manual (American Psychiatric
Association, 2013), the definitio n of post-traumatic stress disorder
(PTSD) requires that there is a single traumatic event which caused a
threat of or actual death or serious injury in order to apply the diagnosis
of PTSD. Hence, although exposure to bullying is associated with the
three symptom clusters, it is still open to discussion whether bullying
can be considered to constitute a life threatening event (Walsh &
Clarke, 2003; Weaver, 2000).
The results from the meta-analyses showed equally strong associa-
tions between exposure to bullying in sc hool and at the workplace.
Hence, this finding supports previous notions a bout similarities and
continuities in bullying among children and adults (Monks et al.,
2009; Smith et al., 2003). Furthermore, this degree of consistency in
the correlates of bullying in different environments and at substantially
different ages points to continuity in the outcomes of bullying. That is,
while it is likely that coping mechanisms and capabilities to respond
to bullying are different between adults and children, there is still an
equally strong direct association between bul lying and symptoms of
posttraumatic stress which operates independently of c ontext and
age. This latter view is supported by findings from study of sense of
coherence as a potential protective factor in the relationship between
workplace bullying and posttraumatic stress which found that sense
of coherence offered the most protective benefits to targets exposed
to low levels of bullying, whereas the benefits of SOC diminished as bul-
lying became more severe (Nielsen et al., 2008). Consequently, bullying
seems to be a traumatic experience for those exposed to it, regardless of
available coping resources.
Table 3
Summary of the meta-analysis of studies on the association between workplace bullying
and PTSD-symptoms (Random effects model).
Sample Association K N Mean
r
95% C.I. Q I
2
Overall PTSD symptom-score
Children Bullying – PTSD 7 2132 .39 .24–.52 71.46⁎ 91.60
Adults Bullying – PTSD 13 4246 .44 .38–.50 53.18 77.44
Total Bullying – PTSD 20 6378 .42 .36–.48 148.93⁎ 87.24
Symptoms of PTSD
Adults Bullying – Hyperarousal 5 1501 .41 .35–.46 5.24 23.62
Adults Bullying – Avoidance 5 1501 .37 .32–.43 4.91 18.55
Adults Bullying – Intrusion 5 1501 .39 .35–.44 2.47 0.00
Note. K = number of correlations; N = total sample size for all studies combined;
mean r = average weighted correlation coefficient; 95% CI = lower and upper limits
of 95% confidence interval
⁎
p b .01
1
PTSD, N. (2006). Facts about PTSD. Psych Central. Retrieved on February 26, 2014, from
http://psychcentral.com/lib/facts-about-ptsd/000662.
21M.B. Nielsen et al. / Aggression and Violent Behavior 21 (2015) 17–24
4.1. Methodological considerations
All the studies we found in our literature review were cross-
sectional and mainly based on survey data, something which limits
the conclusions we can draw from them. Experimental or longitudinal
studies are needed in order to make conclusions about causal factors.
As experimental studies on bullying and po sttraumatic stress would
breach the ethical boundaries for research, longitudinal studies, be it
quantitative or qualitative, should be the preferred method. Building
on findings from longitudinal studies on the relationship between bully-
ing and mental health in general, there are strong reasons to conclude
that bullying does have a negative effect on distress (Finne, Knardahl,
& Lau, 2011; Kivimäki et al., 2003; Lahelma, Lallukka, Laaksonen,
Saastamoinen, & Rahkonen, 2011). For instance, in a recent meta-
analysis of time-lagged associations between bullying and psychological
distress it was established that exposure to bullying was positively
related to subsequent symptoms of distress with an Odds Ratio of 1.68
(Nielsen, Magerøy, Gjerstad, & Einarsen, 2014). However, it was also
found that existing mental health problems increased the risk of being
exposed to bullying at a later time-point with an Odds Ratio of 1.77,
thus indicating a reciprocal relationship between the variables. Hence,
this suggests that it is also import ant to assess vulnerability factors
such as earlier trauma or co-morbid psychiatric disorders.
Earlier studies have shown that parental maltreatment in earlier
childhood can set childre n at risk for victimization by peers
(Shields & Cicchetti, 2001). In this case, the PTSD symptoms might
be attributed to the parental maltreatment and could ve ry well b e
present even before the bullying started. For in stance, personality
traits of neuroticism and introversion, early conduct problems, a
family history of psychiatric di sorde rs, and pre-exi sting psychiat ric
disorders are associa ted with increased risk for exposure to traumat-
ic events (Breslau, 2002). Among children and adolescents, it is also
likely that associations between bullying and symptoms of posttrau-
matic stress can be complicated by family- or home violence, neglect,
or other forms of abuse outside school. In a ddition, there are many
demographical characteristi cs, such as gender, sexual orientation,
race and ethnicity, which may function as vulnerability factors in
the relat ionship between bullying and posttraumatic stress which
remain unaccounted for. With regard to mastery of the trauma, so-
cial support and coping abilities are important moderating fact ors
in the development of symptoms of distress after bullying. However,
no matter the nature or origin of the symptoms, they are noteworthy
for resear chers and for pract ice because of the consistency in the
find ings.
In the vast majority of the reviewed studies on the association
between workplace bullying and PTSD symptoms, assessment of PTSD
symptoms was made by questionnaires like the Impact of Event Scale
(IES; Weiss & Marmar, 1997) and post-traumatic stress scale (Raphael
et al., 1989) with cut-off scores indicating a diagnosis of PTSD
(Creamer, Bell, & Failla, 2003, for IES-R). However, in research on post-
traumatic stress disorder, it is essential to use a strict applic ation of
the diagnostic criteria. App lying symptom checklists can confuse
psychopathology with normal reactions to psychosocial stress or other
psychiatric problems. Their summarized symptoms scores and thresh-
olds defining caseness can fail to ensure fulfillment in the diagnostic
algorithm of PTSD . Basing diagnosis on number and intensity of
symptoms conveyed, rather than adherence to the algorithms of criteria
described in DSM-IV, might lead to over-diagnosis of PTSD. Measuring
symptoms may have useful applications, but it cannot substitute for
assessing full diagnostic criteria (Nemiah, 1995).
4.2. Conclusion and suggestions for future research
Our literature review and me ta-analysis establish an association
between exposure to workplace or school bullying and symptoms of
PTSD with an average weighted correlation of 0.42. An association be-
tween bullying and PTSD is also supported by the fact that an average
of 57% of victims report symptom scores above threshold for caseness
of PTSD. However, due to the limited number of clinical ass essments
of the diagnosis of PTSD, as well as the total lack of prospective studies
on the association it is at this time not possible to conclude whether
expos ure to bullying actually leads to PTSD or whether PTSD is an
adequate diagnosis for targets of bullying. With regard to the PTSD
diagnosis, it should be emphasized that the DSM A-crite rion, as it is
currently described in diagnostic manuals (report of serious injuries or
threats to physical integrity), generally will not be fulfilled by victims
of bullying in that bullying is considered as a non-physical stressor
(
Karatuna & Gok, 2014)
. Alternative, but related diagnoses, such as
adjustment disorder or psychological distress, should, therefore, also
be considered in diagnostic interviews.
Although the number of studies on the relationship between bully-
ing and posttraumatic stress is steadily increasing, and the methodolog-
ical quality of the research is becoming more and more sophisticated,
our understanding of the relationship will benefit from further studies
with more refined research designs. To assess whether bullying at
work or at school can lead to the diagnosis of PTSD, longitudinal studies
with representative samples of persons are needed. The degree of bully-
ing must be assessed by validated questionnaires and a comprehensive
-2,0 -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0
0,0
0,1
0,2
0,3
0,4
Standard Error
Fisher's Z
Funnel Plot of Standard Error by Fisher's Z
Fig. 1. Funnel plot of effect sizes for studies on the association between bullying and symptoms Post Traumatic Stress Disorder (overall).
22 M.B. Nielsen et al. / Aggression and Violent Behavior 21 (2015) 17–24
assessment of risk factors (personality, earlier psychopathology, family
disposition, other life-stress or trauma and social support) must be per-
formed. The past and current psychiatric disorders must be assessed by
validated structured clinical interviews.
In this review and meta-analysis, we have focused on a simple
cause-and-effect relationship between bullying and posttraumatic
stress. However, it is theoretically likely that the relation between the
variables is complex and that more attention should be devoted to iden-
tifying and testi ng plausible mediating and mod erating variables, as
well as reversed associations between variables, in order to fully under-
stand their relationships. While there are some studies on interventions
against bullying and rehabilitation of victims, mainly from research in
schools, there are, to our knowledge, no such studies which assess trau-
ma specific interventions or therapeutic treatment. Hence, an important
issue for upcoming research is to develop sound interventions against
bullying, as well as treatment procedures in the aftermath of bullying,
which can be used to limit the potential traumatic consequen ces of
this form of systematic and persistent mistreatment.
Acknowledgement
We would like to thank Evelyn M. Field and Peggie Partello for their
contributions to the literature search this paper is based upon.
We would also like to thank th e Inte rnational Association on
Workplace Bullying & Harassment (IAWBH) for their contribution to
the Open Access publication of the article.
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