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Running Head: MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
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Psychological Outcomes in Reaction to Media Exposure to Disasters and
Large-Scale Violence: A Meta-Analysis
Tanya L. Hopwood and Nicola S. Schutte
University of New England, Australia
Please direct correspondence to Nicola Schutte at nschutte@une.edu.au
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MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
Abstract
Objective: A quantitative meta-analysis set out to consolidate the effect of experimental studies
of media exposure to disasters and large-scale violence on negative psychological outcomes.
Method: The meta-analysis included 18 experimental studies with an overall sample size of
1634 to obtain an overall effect size and information regarding moderators of the effect size.
Results: An overall significant and large effect size of Hedges’ g of 1.61 showed that across
studies media exposure to disasters and large-scale violence was followed by negative
psychological outcomes. Outcome type was a significant moderator, with anxiety reactions
showing an especially strong effect. Community sensitization was a significant moderator, with
studies conducted in a region that had recently been exposed to the type of disaster or violence
portrayed in the media showing especially large effect sizes. Conclusions: The results indicate
that media exposure to disasters and large-scale violence can cause negative psychological
outcomes, at least transiently. Limitations included a lack of statistical power in some
moderator analyses and the inability to draw inferences about the duration of effects. There is a
need for further research aimed at identifying the possible cumulative effects of media exposure
and identification of groups at greatest risk for harmful outcomes.
Keywords: media exposure, disaster, violence, meta-analysis
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MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
Psychological Outcomes in Reaction to Media Exposure to Disasters and
Large-Scale Violence: A Meta-Analysis
Advances in technology are affording people unprecedented second-hand exposure to
disasters and large-scale violence (Kaplan, 2008; Slone & Shoshani, 2010). Given the vast
number of people consuming modern media and the growing propensity of news outlets to
employ techniques such as rolling coverage of disasters and large scale violence as they occur
(Jain, 2010; Kaplan, 2008), it is increasingly important for research to explore the potential
impact of threat-related content. The purpose of the present study was to consolidate the effect
of experimental studies of media exposure to disasters and large-scale violence on negative
psychological outcomes.
There has been a long-standing academic debate as to whether or not media with
violent content can constitute exposure to violence. Some scholars claim that much of the
research linking violent media to aggressive behaviors has drawn unfounded inferences of
causation from largely correlational research (Grimes & Bergen, 2008). Also, the Diagnostic
and Statistical Manual of Mental Disorders (DSM-5; APA, 2013) has amended the previous
version (DSM-IV-TR; APA, 2000) to explicitly state that media consumption cannot constitute
exposure to trauma for a diagnosis of PTSD. Bolstering the other side of the debate, numerous
studies have found evidence to suggest that media exposure may act as an antecedent of
posttraumatic symptoms (Houston, 2009; Pfefferbaum et al., 2014) and Murray (2008) claimed
that the extant research has supported three types of effects of televised violence – increased
aggression, desensitization, and fear. Further, Wilson (2008) concluded that children’s
extensive use of screen media (including violent material) may affect their socialization,
though these effects may be mediated by factors such as age, gender, the extent to which they
identify with the characters depicted, and how real they believe the media content to be.
While some studies have found either no effect or beneficial effects of disaster-related
media exposure (Williams & Khan, 2007; Linley, Joseph, Cooper, Harris, & Meyer, 2003),
and other researchers have asserted that media exposure may only exacerbate pre-existing
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symptoms of trauma (Ahern et al., 2002), the majority of studies suggest that media
consumption of disaster and large-scale violence-related material may evoke psychological
reactions similar to those experienced by direct victims of trauma (Houston, 2009; Pfefferbaum
et al., 2014; Slone & Shoshani, 2010). Longitudinal and survey studies found that people
distally located from the September 11 terrorist attacks of 2001 and exposed to the events
primarily via mass media experienced significant personal threat and posttraumatic stress
reactions (Callahan, Hilsenroth, Yonai, & Waehler, 2005; Dougall, Hayward, & Baum, 2005;
Schuster et al., 2001; Silver, Holman, McIntosh, Poulin, & Gil-Rivas, 2002). Some studies
found a positive association between hours of September 11 television coverage consumed and
stress reactions (Blanchard et al., 2004; Schlenger et al., 2002), while other researchers
identified a link between disaster-focused distress and perceived similarity to the victims as
depicted by media (Wayment, 2004).
Although substantial research has been conducted in the area of media exposure to
disasters and large-scale violence, most of this research has employed self-report survey
methods. These studies provide valuable details and are rich in ecological validity, collecting
information on how individuals have chosen to consume media and retrospectively recording
subjective reactions. Researchers have examined media forms such as television, newspaper,
radio, and the Internet, and have looked at coverage of both terrorist events and natural
disasters. Many such studies have found strong links between disaster media consumption and
negative psychological outcomes including increased anxiety (Schuster et al., 2001), fear and
depression (Lachlan, Spence, & Seeger, 2009), a heightened sense of threat (Maeseele,
Verleye, Stevens, & Speckhard, 2008), aggression (Argyrides & Downey, 2004), and
posttraumatic stress symptomology (Pfefferbaum et al., 2000; Pfefferbaum, Pfefferbaum,
North, & Neas, 2002; Schlenger et al., 2002).
A recent descriptive research synthesis by Pfefferbaum et al. (2014), which examined
correlational studies of the relationship between disaster-related media consumption and
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psychological outcomes found evidence of an association between television viewing of
disaster news and negative outcomes such as posttraumatic stress (PTS) symptoms, stress
reactions, depression, and fear. Similarly, a meta-analysis by Houston (2009) found a
significant overall effect size (r = .162) for the relationship between terrorism-related media
consumption and PTS. However, as with the individual studies, the correlational nature of the
data comprising these meta-analyses does not allow for inferences regarding causality; people
who watch traumatic events on the news may consequently experience fear. Alternatively,
people experiencing fear may watch traumatic news, perhaps for information-seeking,
surveillance purposes, or reassurance.
Longitudinal studies that measured psychological dimensions pre- and post-disasters
(Cohen et al., 2006; Kennedy, Charlesworth, & Chen, 2004; Otto et al., 2007; van Zelst, de
Beurs, & Smit, 2003) have helped support the theory of media exposure to disasters and large-
scale violence effecting negative psychological outcomes. These studies, while again high in
ecological validity, cannot control for a range of potentially confounding exposure variables
and so are unable to isolate the effects of media.
Although many researchers have used experimental methods to explore individual
psychological reactions to media exposure to disasters and large-scale threats, no meta-analysis
of these studies exists. By conducting a meta-analysis of experimental studies of media
exposure to disasters or large-scale violence, we aimed to identify an overall effect size for
psychological outcomes and also consolidate information regarding the main types of reactions
to such media exposure. A review of the literature indicated that anxiety (or stress) and anger
are commonly measured outcomes (Lerner, Gonzalez, Small, & Fischhoff, 2003; Pfefferbaum
et al., 2014). As pointed out by Slone and Shoshani (2010), the experience of these emotions
is predicted by the theory of protection motivation (Rogers, 1983). This theory asserts that
when a person interprets a situation as threatening, anxiety will often result. This anxiety may
promote a need to defend the self and others, which may in turn lead to anger. We believe that
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this theory may help provide a useful scaffold for understanding how media exposure to
disasters and large-scale violence may communicate a sense of personal or community threat,
which may in turn provoke reactions such as anxiety, anger, and other forms of negative affect.
Another theory that may add to the conceptual framework for understanding people’s
reactions to this type of media content is the conservation of resources theory (Hobfoll, 1993).
The conservation of resources theory claims that a person’s ability to cope with challenges
depends upon his or her perceived inventory of practical, social, and emotional resources.
Maguen et al. (2008) posited that large-scale threats (such as terrorism) intensify perceptions of
resource loss in areas such as self-esteem, self-efficacy, and internal locus of control. The loss
of these safeguarding resources may increase levels of negative affect and diminish adaptive
coping (Moos & Holahan, 2003). Brewin et al. (2000) showed that many studies have
supported a cascading effect of perceived resource loss, with multiple stressors leading to
increased vulnerability to further stress. If it can be demonstrated that one-time media
exposure to disasters or large-scale violence plays a causal role in negative psychological
outcomes – even transiently – this may suggest the presence of maladaptive and more enduring
effects in some individuals due to cumulative long-term exposure.
In the current meta-analysis, we predicted that across studies there would be a
significant effect size for the impact of media exposure to disasters or large-scale violence on
negative psychological outcomes. There are a number of variables that we believed might
moderate outcomes across studies: Intentionality of the event portrayed; media format; whether
the study was conducted before or after September 11; community sensitization to trauma in
relation to the sample; differences in participant sample gender and age. The background for
selection of these moderator variables follows.
Intentionality of Event
Research has indicated that a disaster designed with human intent (e.g., a terrorist
attack) may be associated with a higher risk of subsequent psychopathology than a disaster of
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accidental or natural origin (DiMaggio & Galea, 2006). Also, research results have suggested
that different forms of emotions may be more common in the wake of accidental versus
intentional trauma (e.g., anger for intentional events, fear for random events; Rosoff, John, &
Prager, 2012). We examined whether portrayals of intentionally created disasters would result
in stronger negative psychological outcomes.
Media Format
Communications research has provided evidence for the efficacy of video footage,
compared with more traditional forms of media such as newsprint or radio, in creating a more
emotionally arousing experience, a sense of realism that has been referred to as presence
(Lombard & Ditton, 2006). Graphic footage of disasters may evoke a sense of immediacy and
engagement, and perhaps even a potent communication of threat (Callahan et al., 2005; Cho et
al., 2003). Meta-analytic studies and research syntheses of correlational research (Houston,
2009; Pfefferbaum et al., 2014) indicated that consumption of disaster or large-scale threat
news via television is significantly associated with numerous negative psychological outcomes
including PTSD, PTS, depression, anxiety, and anger. We examined whether video portrayal
of disasters would be associated with larger effect sizes.
The Impact of September 11
Much research on media consumption of disasters and large-scale violence occurred in
the wake of the terrorist attacks in the USA on September 11, 2001 (Neria & Sullivan, 2011).
The rolling coverage of these events in the media, continued for days and then sporadically
during the weeks and months that followed, giving millions of people across the globe access
to details of the disaster (Pfefferbaum et al., 2002). The extensive coverage and large scale of
the mass casualties that occurred may have evoked changes in belief systems related to safety
and security for many individuals (Linley et al., 2003). We examined whether post-September
11 studies would show stronger effect sizes.
Community Sensitization to Trauma
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While some theorists contend that previous exposure to trauma may serve as a form of
inoculation against adversity (Eysenck, 1983, as cited in Shrira, Palgi, Hamama-Raz,
Goodwin, & Ben-Ezra, 2014), many studies have indicated that a history of previous trauma
increases susceptibility to adverse psychological outcomes, such as PTSD (Brewin, Andrews,
& Valentine, 2000; Chatard et al., 2012; Shrira et al., 2014). Some global locations have had
more recent direct experience of disasters (e.g., war, terrorism, disease, and natural disasters)
than others. In the current meta-analysis, the global region in which each experiment was
conducted was coded as a possible moderator variable. Also, an additional variable called
community sensitization was created to identify whether or not the region in question had
recently (within the previous 5 years) experienced a disaster of the type portrayed in the
stimulus material. We examined whether studies conducted in areas that have recently
experienced large-scale disaster or violence would show larger effect sizes.
Individual Differences
In the correlational research of media consumption of disasters and large-scale violence
and psychological outcomes, the most widely replicated moderating variable is gender, with
females consistently demonstrating greater susceptibility to negative outcomes than males
(Baum, Rahav, & Sharon, 2014). It has been suggested that this gender effect may be partially
accounted for by women’s higher levels of fear for others (altruistic fear; Nellis & Savage,
2012), heightened empathy (Nellis, 2009), increased levels of perceived vulnerability (Baum et
al., 2014; Nellis, 2009), or greater propensity to acknowledge distress (Lachlan, Spence, &
Nelson, 2010). We examined whether studies with a higher percentage of females would show
stronger effect sizes.
Eysenck’s (1983) inoculation theory (as cited in Shrira et al., 2014) suggests that older
people have experienced more challenges across their lifetimes and have thus developed greater
resilience – a quality that may help protect them from the adverse effects of further trauma.
Some correlational studies have found evidence to support these inoculation and maturation
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effects (e.g., Shrira et al., 2014; Schlenger et al., 2002). However, other studies have found that
elderly people may be more susceptible than younger people to PTSD and other detrimental
outcomes (e.g., Kun, Han, Chen, & Yao, 2009). Further, many researchers have contented that
children may be a particularly vulnerable population in terms of adverse PTS reactions (Comer
& Kendall, 2007; Dirkzwager, Kerssens, & Yzermans, 2006; Pfefferbaum, 1997; Saylor,
Cowart, Lipovsky, Jackson, & Finch, 2003). We examined whether studies of adults with older
participants would show stronger effect sizes and whether studies with child participants would
show stronger effect sizes.
Current Study
The current study aimed to consolidate findings of experimental research providing
information regarding the causal impact of disaster-related media exposure on psychological
reactions through a meta-analysis. Our predictions are as follows.
Hypothesis 1: Across studies there is a significant effect size for the impact of media exposure
to disasters or large-scale violence on negative psychological outcomes.
Hypothesis 2: Media portrayals involving intentionality result in stronger negative
psychological outcomes.
Hypothesis 3: Video portrayal results in larger effect sizes.
Hypothesis 4: Post-September 11 studies show larger effect sizes.
Hypothesis 5: Studies conducted in areas recently experiencing large scale disaster or violence
show larger effect sizes.
Hypothesis 6: Studies with a higher percentage of females show larger effect sizes.
Hypothesis 7: Studies with older participants or child participants show stronger effect sizes.
Method
Inclusion and Exclusion Criteria
Studies were deemed eligible if they used an experimental methodology in a controlled
environment to measure individuals’ psychological outcomes in response to media coverage of
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disasters or large-scale violence. The key terms were operationalized as follows: Media
coverage (the independent variable - IV) included factual reports from television, Internet,
radio, newspaper articles, or realistic simulations of any of the above. Disasters or large-scale
violence included major accidents (e.g., plane crashes or multiple road accidents), natural
disasters (e.g., hurricanes), acts of terrorism, war or combat, climate change, economic crises,
and crime with the potential for casualties. Psychological outcomes (the dependent variable -
DV) included state anxiety, negative affect, fear, or perceived threat from the type of trauma in
the exposure condition. The DV could also include other negative outcomes – either emotional
or cognitive – such as anger or blame, or positive outcomes such as trust and empathy. One
might expect outcomes such as trust to decrease after some media exposure, such as coverage
of a terrorist attack, and other outcomes, such as empathy, to increase after other media
exposure, such as coverage of a natural disaster.
Eligible studies needed to either assign groups across the IV (e.g., media exposure to
disaster or large-scale threat content versus neutral content) or use repeated measures, with pre-
and post-exposure measures on the DV. Given the meta-analysis aimed to assess effect size
variability across ages, genders, and locations, eligible populations included the general public
in any geographical region.
Search Strategies and Data Extraction
In June and July 2015, the PsycARTICLES, ProQuest, and Summon bibliographic
databases were used to carry out a systematic search for experimental studies measuring
psychological outcomes in the context of media exposure to disasters and large-scale
violence. Keywords included “media coverage”, “media exposure”, “television news”,
“disaster media coverage”, “newspaper”, “internet news”, “terrorism”, “war”, “natural
disaster”, “virus”, “pandemic”, “crime”, “anxiety”, “negative affect”, “fear”, “threat”,
“anger”, “positive affect”, “experiment”. A series of search expressions were created for
each disaster type to cover all relevant possibilities [e.g., terrorism AND (“media
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coverage” OR “television news”) AND (anxiety OR “negative affect” OR fear OR threat
OR anger OR “positive affect”) AND experiment].
To ensure that the search was methodical and met recommended guidelines for
meta-analysis research, the PRISMA search protocol (Moher at al., 2009) was used to
record all articles identified, screened, and assessed for eligibility. The reference list of
each eligible article was reviewed and assessed for additional relevant studies, and Google
Scholar was used to search for relevant research by identified experts in the field.
Separate eligible reports by the same research teams were examined to ensure the use of
independent data sets.
Finally, each study was assessed to determine if adequate information was provided
to ensure suitability of the stimulus material (exposure group media content) and if the
methodology was appropriate for the purpose of determining a causal relationship between
the IV and DV. Studies were excluded if there was insufficient data to allow for the
calculation of an effect size of at least one relevant DV.
In total, 4364 reports were identified through the database searches, with an
additional 137 reports obtained through other sources, such as a search of literature cited
in pertinent articles. After removal of duplicate items, 2565 records remained. Screening
via title and abstract (and full-text where necessary) resulted in the exclusion of 2523
reports that either did not employ an experimental methodology, did not manipulate an
appropriate form of media exposure, or did not measure a relevant outcome. Of the
remaining 42 eligible reports, 3 were excluded due to insufficient information regarding
the stimulus media material, 20 were excluded due to methodologies that were
incompatible with the research question (e.g., correlational studies), and 4 were excluded
due to insufficient reported data to allow for calculation of an effect size of at least one
relevant DV. Ultimately, the search resulted in 15 reports containing 18 studies suitable
for inclusion in the meta-analysis (see Table 1). Some groups that were not appropriate
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for testing our hypotheses (such as those using a treatment condition prior to media
exposure) were excluded; the experimental groups excluded from each study and the
rationale for these decisions are outlined in Table 2. The overall sample size was 1634,
with 959 females (58.7%) and 675 males (41.3%).
Publication Status of Studies
Several eligible unpublished reports were located during the search phase but were
excluded due to incompatible methodologies or insufficient information. Thus, all studies
included in the meta-analysis were published.
Coding Procedures
Following the recommendations of Cooper (2010), all studies were coded
separately by two raters. The coding was consistent across raters (97% agreement) and
disparities were resolved through discussion.
Outcome types. The studies included in the meta-analysis measured a variety of
psychological outcomes, most considered negative (e.g., state anxiety, anger, perceived
threat) but some with positive valence (e.g., trust and empathy). To allow us to investigate
whether type of outcome impacted effect size, each outcome in each study was coded in
one of six broad categories – state anxiety, negative affect, fear, perceived threat, other
negative outcome (e.g., anger), and positive outcome.
Moderator variables. Based on the findings of correlational research and the theories
espoused by previous researchers (as mentioned in the introduction), several study variables
were coded with the aim of assessing their influence on the effect size of psychological
outcomes. Moderator variables included: Intentionality (intentional, unintentional, mixture);
Media format (video, audio, print, static images, mixed); Date of study (pre- or post-September
11, 2001); Global location (USA, Middle East, Europe/GB, Asia, Australia, other);
Community sensitization to disaster-type (exposure or no exposure to given disaster type
within the previous 5 years); Gender breakdown (percentage of females); Mean age of
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participants.
Study quality. Given the potentiality for study quality to impact results, study
design and the reliability of psychometric measures (for DVs) were coded as moderator
variables. Study design was coded with four levels of empirical design: 1. Pre-post
measures with no control group; 2. Experimental and control groups with no random
assignment; 3. Random assignment to experimental and control group – post test only; and
4. Random assignment to experimental and control group – pre and post measures. The
reliability of psychometric measures for the outcomes (DVs) was coded as a continuous
variable, with a mean Cronbach’s alpha calculated for outcomes in each study (five of the
18 studies had missing data for this variable).
Data Analysis
All data analyses were performed using Comprehensive Meta Analysis Version 3
(CMA; Biostat Inc., 2013). As most studies reported results in the form of means (and
standard deviations) for exposure and control groups, and based on the recommendation of
Borenstein, Hedges, Higgins, and Rothstein (2009), Hedges’ g was chosen for the effect size
metric. The meta-analysis provided a weighted mean summary effect size for negative
psychological outcomes. Positive outcomes (e.g., trust and empathy) were included but were
entered to reflect an opposite effect direction where appropriate. For the main analysis, if
outcomes of different types were reported for the same group of participants in a study, the
outcomes were averaged. Raw effect sizes (assuming independence of outcomes) for each
coded outcome type were also calculated and are reported in Table 1). Subgroup analyses (for
the categorical moderator variables) and meta-regressions (for the continuous variables) were
based on averaged outcomes for those studies with multiple outcomes.
A subgroup moderator analysis was conducted to find weighted effect sizes for each
type of psychological outcome represented (e.g., state anxiety, negative affect, positive
outcomes). In order to make full use of available information regarding different types of
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outcomes, in this analysis each outcome from studies reporting information for multiple
outcomes was used.
According to Borenstein et al. (2009), a random effects model is the appropriate
computational model for most meta-analyses in the social sciences, where it usually cannot be
assumed that the primary studies will yield the same effect size. In contrast, a fixed effects
model is appropriate when it can be assumed that all studies are measuring the same effect in
the same population. In the case of the current meta-analysis, given the variations in study
design, participant groups, locations, and outcomes measured, the effect sizes were expected to
vary and a random effects model was used.
Heterogeneity Analyses
Inspection of heterogeneity statistics revealed a significant Q-statistic (Q = 378.53, p
< .001) and a high I2 index (p < .001, I2 > 75%). These results indicate high heterogeneity,
with the effect sizes across studies varying significantly (Cochran, 1954; Higgins &
Thompson, 2002). This variation supports the decision to use a random effects model, as the I2
index (I2 = 95.51%) indicates that approximately 96% of the variance across studies is due to
difference in the true effect sizes, rather than sampling error. The high heterogeneity found
here also supports the decision to explore potential moderator variables.
Results
Overall Mean Effect Size
In order to test the major hypothesis that media exposure to disasters or large-scale
violence results in negative psychological outcomes, a mean effect size was calculated for all
studies included in the meta-analysis (k = 18). All effect sizes are presented as standard mean
differences in the metric of Hedges’ g (see Table 1). All except one study (Williams & Khan,
2011, with g = -1.43) showed a mean effect size indicating an increase in strength in negative
psychological outcomes. The overall mean weighted effect size for negative psychological
outcomes was large, g = 1.61 (SE = 0.27, 95% CI [1.07, 2.14], p < .001), indicating that across
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studies media exposure to disasters or large-scale violence had a significant effect on negative
psychological outcomes.
Moderator Analyses
Method of moments meta-regression examined the association between percentage of
females in samples, reliability of measures, and mean age of samples with effect size. The
percentage of females was significantly associated with the effect size (slope = -0.059, SE =
0.025, CI [-0.108, -0.009], Z = -2.31, p < .05). These results indicate that the higher the
percentage of female participants, the weaker the impact of media exposure on negative
psychological outcomes. However, the regression slope indicated only a very small
association. The meta-regression for reliability of measures also found a significant
association (slope = -0.059, SE = 0.025, CI [-0.108, -0.009], Z = -2.31, p < .05). These results
indicate that the higher the mean reliability level of measures in each study, the stronger the
effect of media exposure on negative psychological outcomes.
Using a linear meta-regression, the mean age of samples was not significantly
associated with the effect size (Z = 0.30, p = .76), indicating that a change in mean age of
participants did not correspond with a linear change in psychological outcomes. Because we
predicted a non-linear relationship (with effects for both children and older people predicted to
be greater than young or middle aged people), a curvilinear meta-regression using a quadratic
model was used to test this hypothesis. The curvilinear model, although not significant (Z = -
1.60, p = .11) approached a better fit for the data than did the linear model.
Results of the categorical moderator analyses are shown in Table 3. Intentionality of
the event portrayed did not moderate the effect size, Q(1) = 2.73, p = .098. The effect size
difference between the pre- and post-September 11 groups also was not significant Q(1) =
0.52, p = .47. However this test lacked power; with only 2 studies being conducted prior to
September 11, 2001.
Grouping by media format did not yield a significant difference across effect sizes,
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Q(3) = 5.99, p = .112. As one sub-category of this variable was a mixture of the other formats,
a repeat analysis excluded the study that used a mixed media format and yielded a result
trending towards significance, Q(2) = 5.15, p = .076. Due to an under-representation of
subgroups (no studies used audio, three used print, and three used images), these results should
be interpreted with caution.
Global location significantly moderated the effect size, Q(3) = 36.17, p < .001, as did
sensitization to disaster type, Q(1) = 18.54, p < .001. The results showed that studies
conducted in the Middle East showed the highest effect sizes. The results also indicated that
studies conducted in communities with a recent history (within the previous 5 years) of the
type of disaster portrayed showed larger effect sizes than did studies conducted in communities
without this type of threat salience.
Given that the studies in the meta-analysis measured different types of psychological
outcomes, we examined whether the type of outcome moderated the effect size. As the mean
effect across outcomes for studies with multiple outcomes could not be used here, we ran this
analysis with the assumption of independence of outcomes within each study (see Table 4).
This assumption of a zero correlation between outcomes represents a conservative approach; it
inflates the p-value, lowering the statistical power to detect heterogeneity (Borenstein et al.,
2009). The result of this moderator analysis was significant, Q(4) = 24.65, p < .001, indicating
that the strength of the effect varied across the types of outcomes measured. State anxiety, the
most commonly measured outcome type (k = 12) was associated with the strongest effect, g =
3.11, SE = 0.38, CI [2.368, 3.849], Z = 8.23, p < .001.
Publication Bias
A potential source of bias in meta-analyses is publication bias, due to the potential for
studies with significant results to be more abundant in the published literature and more easily
located by researchers than studies reporting no effects (Borenstein et al., 2009; Cooper, 2010;
Rosenthal, 1979). To check for publication bias, Duval and Tweedie’s (2000) trim and fill
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procedure with funnel plot and a classic fail-safe N test (Rosenthal, 1979) were conducted
using CMA. The funnel plot showed little asymmetry and Duval and Tweedie’s trim and fill
found no missing studies to the left of the mean, indicating no likelihood of publication bias.
The fail-safe N value (1681) far exceeded the minimum recommended critical value of 100
(given by 5k +10, where k is the number of studies in the meta-analysis; Rosenthal, 1991).
This suggests that one would need to add 1681 studies that found no effect of media exposure
on psychological outcomes to render the effect non-significant. Given these findings, there is
no evidence of publication bias.
Discussion
A large meta-analytic effect size showed that, across experimental studies, media
exposure to disasters and large-scale violence resulted in increased negative psychological
outcomes. This result, supporting the main hypothesis of the meta-analysis, suggests that
such media exposure results in negative psychological outcomes. The finding of a causal
impact across experimental studies adds to previous findings generated by correlational
and longitudinal studies.
Of the categorical moderators of effect size examined, community sensitization,
global region, outcome type, and study design all had significant associations with
negative psychological outcomes. For continuous moderator variables, percentage of
females and reliability of outcome measures both reached significance. No statistically
significant differences were found for the other moderator variables.
Hypothesis 2, that media portrayals involving intentionality result in stronger negative
psychological outcomes, was not supported, even though there was a weak trend towards
significance, with intentionally caused disaster or violence having a larger effect. Hypothesis
3, that video portrayal results in larger effect sizes, also was not significant, but trended
towards significance, with video footage evoking a stronger negative psychological outcome
than print or static images. This trend is consistent with previous research supporting the
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ability of video to imbue the consumer with a more emotionally arousing experience and
perhaps a potent communication of threat (Callahan et al., 2005; Cho et al., 2003). Hypothesis
4, that post-September 11 studies would show larger effect sizes, was not supported.
Hypothesis 5 focused on community sensitization in that we expected that studies
conducted in areas recently experiencing large-scale disaster or violence show larger effect
sizes. Analysis of the moderator variable community sensitization showed that effect sizes
were significantly larger for studies conducted in a region that had recently been exposed to the
type of disaster or threat portrayed in the media. This finding further bolsters the theory of
cumulative adverse effects, in line with the conservation of resources theory, and is also
consistent with research on complex trauma and poly-victimization. A national study
conducted by Turner, Finkelhor, and Ormrod (2010) indicated that multiple incidences of
trauma for children (across varying types of victimization) was linked to adverse psychological
outcomes. The results suggested that cumulative episodes of adversity may be more strongly
related to negative outcomes than are single events or even repeated occurrences of the same
type of abuse. If, as the current results suggest, media coverage of disasters and traumatic
events has the potential to cause transient negative psychological changes in individuals, then it
is possible that cumulative effects over time (or intense prolonged exposure) may generate
more serious adverse outcomes.
Related to the community sensitization hypothesis, effect sizes varied across global
regions. Studies conducted in the Middle East showed much higher effect sizes than studies
from other regions. Given the historical incidences of war and terrorist attacks in this region
(Solomon, Gelkopf, & Bleich, 2005), these results suggest that the cumulative effects of this
type of trauma may render people more susceptible towards negative reactions to media
exposure to disaster and large-scale violence. Again, this is consistent with previous research
showing that multiple stressors over time or a history of trauma may render people more
vulnerable to mental health disorders such as posttraumatic stress disorder and anxiety or mood
18
MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
disorders (Brewin et al., 2000; Myers et al., 2015). Similarly, a meta-analysis of studies
examining the behavioral consequences of terrorism showed that a history of diagnosed mental
health problems was strongly associated with PTSD following a terrorist incident (DiMaggio
& Gale, 2006).
Hypothesis 6, predicting that studies with a higher percentage of females show larger
effect sizes, was not supported. In the current study, the meta-regression using percentage of
females as a covariate provided a statistically significant model; but the association was small
and not in the expected direction. This is not consistent with gender effects having been found
frequently in previous research (e.g., Baum et al., 2014), with females found to be more at risk
of adverse outcomes related to media exposure and to other forms of indirect exposure to
trauma. Future research might further explore the effect of gender on reaction to media
exposure.
Hypothesis 7 predicted that studies with older participants or child participants would
show stronger effect sizes. The meta-regressions for mean age – using both linear and
curvilinear models – did not reach significance. As a group, children were underrepresented in
the meta-analysis, with only two studies using child participants. Similarly, older adults were
not well represented, with the highest mean age for a study being 41.47. Given this lack of
variability in mean age, these findings should be interpreted with caution. These results can be
viewed in the context of previous research that has presented mixed results regarding age effects
on outcomes relating to media and other forms of indirect exposure to trauma (e.g., Kun et al.,
2009; Shrira et al., 2014).
Exploratory moderator analyses investigated effects for different outcomes and aspects
of methodology. The included studies measured a variety of psychological outcomes. State
anxiety was the most measured and strongest outcome. This result is consistent with
correlational research reporting a link between media consumption of disaster-related content
and anxiety (Cohen et al., 2006; Schlenger, 2002; Schuster et al., 2001; Sugimoto, 2012). The
19
MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
overall effect size for perceived threat was not significant, which is inconsistent with many
previous correlational research findings (Fahmy & Johnson, 2007; Nabi & Sullivan, 2001;
Nellis & Savage, 2012; Ridout, Grosse, & Appleton, 2008) and what would be predicted based
on protection motivation theory. One possible explanation for this may be the laboratory
conditions attached to the studies; perhaps the artificial environment reminded participants that
the media content was not necessarily temporally or personally relevant. Thus, although the
media content may have evoked negative emotions and anxiety, a perceived lack of personal
involvement or perceived reality may have reduced estimations of threat (Roser & Thompson,
1995; Wilson, 2008).
In relation to methodology, both study design and reliability of measures were
significant moderators. Studies with random assignment to groups and pre-post measurement
showed stronger effect sizes. Studies using measures with greater reliability showed stronger
effect sizes. These results suggest that the more exact the methodology, the larger the effect
sizes, and bolster confidence in the overall effect found in the meta-analysis.
The findings of the current study, in part, support the proffered theoretical framework
based on protection motivation theory and conservation of resources theory. As predicted by
protection motivation theory, the significant and strong overall effect size for state anxiety is
consistent with expectations of anxiety and stress arising due to threatening events. However,
the failure of the overall effect size for perceived threat to reach significance is inconsistent
with a model of perceived threat being a necessary precursor to anxiety. This suggests that
there are additional pathways between the consumption of the media report and feelings of
anxiety or stress.
An improved conceptual framework might include mechanisms such as emotional
contagion – the process whereby individuals tend to unconsciously mimic the affect of others,
producing an authentic subjective experience of the emotion (Hatfield, Cacioppo, & Rapson,
1993). Watching the suffering of other people may evoke feelings of empathy and
20
MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
identification, thus facilitating the process of emotional contagion, evoking feelings of anxiety
and stress to mirror those of depicted victims (Nummenmaa, Hirvonen, Parkkola, & Hietanen,
2008).
Conservation of resources theory predicts that a cumulative burden of adversity will
diminish an individual’s perceived store of psychological resources and increase vulnerability
to future trauma. This part of the conceptual framework was supported by the current results
relating to community sensitization and is consistent with recent findings regarding complex
trauma and poly-victimization (Turner et al., 2010). These findings support the possibility of
negative outcomes amassing in individuals due to repeated exposure to media reports of
disasters or large-scale violence.
Limitations
A large number of datasets were provided by two teams and, although we took care to
ensure that the datasets themselves were independent, the results should be interpreted with
caution. It should be noted that the largest effect sizes appear to be impacted by the moderator
variables shown to be associated with greater effects (e.g., Middle East location, intentional
acts, video presentation, community sensitization), a pattern that is consistent with our major
findings. When considering the results from the different teams, it may be useful to be mindful
of the significant differences between the populations studied.
Due to a lack of studies in some subgroups, several moderator analyses lacked
statistical power and thus may have failed to detect real differences. For example, in relation
to the pre or post September 11 moderator, only two studies were conducted before September
11. Most of the studies included in the meta-analysis were conducted in laboratory
settings, used one-time exposure to the stimulus material, and measured immediate
psychological outcomes. While this methodology is beneficial in terms of minimizing the
influence of confounding variables, it reduces ecological validity. People may have
different reactions in real-world situations due to autonomy in selection of media content,
21
MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
social support, and a myriad of other variables that may affect outcomes. The included
studies examined only short-term effects of trauma-related media exposure. Longer
detrimental (or beneficial) outcomes were not assessed due to the time-limited nature of
the experimental designs used. Thus, it is unknown how transient or enduring these
effects may be.
Research Implications
Future experimental studies with a longitudinal component could assess the
longevity of psychological responses to media exposure, particularly cumulative effects.
Future studies might also identify groups at risk for intense or longer-lasting effects,
including potential effects for children and elderly adults. Finally, future studies might
investigate the impact of understudied media modalities, such as audio presentations, and
emerging future modalities, such as virtual reality presentations.
Clinical and Policy Implications
In conjunction with correlational research linking media consumption with anxiety,
post-traumatic stress symptoms, stress reactions, depression, anger, and fear (Houston, 2009;
Pfefferbaum et al., 2014), the results of the present meta-analysis of experimental studies
suggest that media consumption can be a source of psychological distress. Clinicians might
consider discussing media consumption with distressed clients to assess whether types of
media viewed may be a source of distress for clients. Media professionals might consider the
impact of media coverage on consumers, especially on viewers who might be sensitized to
experience negative reactions, particularly viewers in areas experiencing disasters or violence
such as that portrayed in the media coverage.
Conclusion
People have more access than ever before to graphic media coverage of disasters
and large-scale violence. Given the ubiquitous nature of bad news in the modern world, it
is important to understand the psychological outcomes associated with exposure to this
22
MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
type of media. The results of the current meta-analysis suggest that media exposure to
disasters or large-scale violence plays a causal role in negative psychological outcomes, at
least transiently. Further, people in communities with a recent history of disaster or large-
scale violence may experience greater negative psychological outcomes due to media
portrayal of a similar event. Additional research is needed to determine which populations
are most at risk for negative reactions and what factors may attenuate these effects.
Future research should also explore the potential consequences of cumulative effects or
prolonged exposure to media coverage of disasters or large-scale violence, particularly for
vulnerable individuals.
23
MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
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*Slone, M., & Shoshani, A. (2008). Indirect victimization from terrorism: A proposed post-exposure
intervention. Journal of Mental Health Counseling, 30(3), 255-266. Retrieved from
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9559-bc87487013c3%40sessionmgr4001&crlhashurl=login.aspx%253fdirect%253dtrue
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448. doi:10.1002/j.1556-6678.2010.tb00044.x
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MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
Table 1
Characteristics of Included Studies and Effect Sizes
Authors (year/study no.) nMean
age
%FemaleaDisaster type Intent.bMedia Study
designc
Location SensitizationdOutcome Reliability
(^) e
ESf Mean
ES
Barlett and Anderson (2014/2) 101 19.24 73 Other (Econ.) U Video 3 USA No Neg. .91 1.028 1.028
Boyle (1984) 58 22.60 83 Acc./Nat. U Video 1 AUS Yes SA NR 0.759 0.607
Boyle (1984) 58 22.60 83 Acc./Nat. U Video 1 AUS Yes Neg. NR 0.532 0.607
Comer et al. (2008) 120 10.80
g
61hTerrorism
I
Video
1
USA
No SA .88
0.832 0.504
Comer et al. (2008) 120 10.80
g
61hTerrorism
I
Video
1
USA
No PT .84
0.341 0.504
Fischer et al. (2007/2) 60 30.37 52 Terrorism I Print 3 EUR/GB No PT NR 0.520 0.520
Fischer et al. (2007/4) 67 24.68 81 Mixture M Images 3 EUR/GB No Neg. .86 0.401 0.542
Fischer et al. (2007/4) 67 24.68 81 Mixture M Images 3 EUR/GB No Pos. .87 0.683 i 0.542
Fischer et al. (2010/1) 80 27.43 63 Terrorism I Mixed 3 EUR/GB No PT .84 0.561 0.561
Fischer et al. (2010/3) 22 41.47 73 Terrorism I Images 3 EUR/GB Yes PT NR 1.950 1.950
Fischer et al. (2011/1) 40 25.67 50 Terrorism I Images 3 EUR/GB No NA .86 1.021 0.496
Fischer et al. (2011/1) 40 25.67 50 Terrorism I Images 3 EUR/GB No PT .79 0.598 0.496
Fischer et al. (2011/1) 40 25.67 50 Terrorism I Images 3 EUR/GB No Pos. .88 0.183 i 0.496
Fischer et al. (2011/2) 40 26.85 50 Terrorism I Print 3 EUR/GB No NA .86 0.780 0.542
Fischer et al. (2011/2) 40 26.85 50 Terrorism I Print 3 EUR/GB No PT NR 0.456 0.542
Fischer et al. (2011/2) 40 26.85 50 Terrorism I Print 3 EUR/GB No Pos. NR 0.466 i 0.542
Lightstone et al. (2005) 116 NR 78 Terrorism I Print 4 USA Yes SA .89 0.857 0.857
Ortiz et al. (2011) 248 9.24 54 Acc./Nat. U Video 3 USA Yes SA .85 0.427 0.427
Shoshani and Slone (2008) 100 22.65 50 Terrorism I Video 4 ME Yes SA .95 11.034 7.910
29
MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
Shoshani and Slone (2008) 100 22.65 50 Terrorism I Video 4 ME Yes Neg. .94 8.241 7.910
Shoshani and Slone (2008) 100 22.65 50 Terrorism I Video 4 ME Yes Pos. .83 6.182 i 7.910
Slone (2000) 237 34.70 50 Terrorism I Video 4 ME Yes SA .94 1.662 1.662
Slone and Shoshani (2006) 43 22.65 50 Terrorism I Video 4 ME Yes SA .92 5.122 5.023
Slone and Shoshani (2006) 43 22.65 50 Terrorism I Video 4 ME Yes Neg. .91 4.925 5.023
Slone and Shoshani (2008) 84 22.65 50 Terrorism I Video 4 ME Yes SA .95 6.588 3.603
Slone and Shoshani (2008) 84 22.65 50 Terrorism I Video 4 ME Yes Neg. .94 0.617 3.603
Slone and Shoshani (2010) 100 23.00 50 Terrorism I Video 4 ME Yes SA .95 10.823 8.916
Slone and Shoshani (2010) 100 23.00 50 Terrorism I Video 4 ME Yes Neg. .94 7.009 8.916
Williams and Khan (2011) 40 NR 50 Terrorism I Video 3 USA No SA .89 -1.429 -1.429
Zeidner et al. (2011) 78 24.44 59 Terrorism I Video 3 ME Yes NA .90 0.768 0.661
Zeidner et al. (2011) 78 24.44 59 Terrorism I Video 3 ME Yes PT .90 0.768 0.661
Zeidner et al. (2011) 78 24.44 59 Terrorism I Video 3 ME Yes Pos. .94 0.447 i 0.661
Note. NR = not reported; USA = United States of America; AUS = Australia; EUR/GB = Europe or Great Britain; ME = Middle East; Acc./Nat. = Large-scale accident or natural
disaster; Econ. = Economic crisis; SA = State anxiety; NA = Negative affect; PT = Perceived threat; Neg. = Other negative psychological outcomes; Pos. = Positive psychological
outcomes.
a The percentage of females in the sample to the nearest whole percent. Studies reporting a fairly even gender breakdown were coded as 50%.
b Intent. = Intentionality; I = Human agency intentional event; U = Unintentional event; M = Mixture of intentional and unintentional events.
c 1 = Pre-post with no comparison group; 2 = Experimental and control groups with no random assignment; 3 = Random assignment experimental and control group – post test
only; 4 = Random assignment experimental and control group – pre and post.
d Sensitization indicates whether the location had a history of the disaster type portrayed in the media within 5 years prior to study publication.
e Cronbach’s alpha values for reported reliability were averaged when more than one measure for that outcome type was recorded for the study.
f Raw effect size for the outcome type, assuming independence of the data for each outcome. Raw effect sizes are shown averaged when more than one measure for the outcome
type (e.g., for type other negative effect) was recorded for the study.
g The mean age for child participants in the study (n = 90); A subgroup of mothers was also included (n = 30), but no age data were reported.
h The percentage of females across both child and adult participants in the study (48% for child sample;100% for adult sample).
i For positive outcomes a high score indicates a less positive outcome.
30
Running Head: Media Exposure to Disasters and Large-Scale Violence
Table 2
Sample Numbers Used and Excluded from Each Study and Exclusion Reason
Authors (Year/Study No.) n used n excluded Exclusion reason
Barlett and Anderson
(2014/2)
101 0
Boyle (1984) 58 0
Comer et al. (2008) 120
(90 children,
30 mothers)
60 mothers Excluded mothers who were given
experimental training pre-media
exposure.
Fischer et al. (2007/2) 60 0
Fischer et al. (2007/4) 45 22 for each
comparison
test
Both experimental groups compared
individually against control (neutral
media) group.
Fischer et al. (2010/1) 80 0
Fischer et al. (2010/3) 22 parents 22 children Children did not view media.
Fischer et al. (2011/1) 40 20 Meaning group excluded as this could
be interpreted as an amelioration
intervention that would affect
outcome.
Fischer et al. (2011/2) 40 20 As above.
Lightstone et al. (2005) 116 0
Ortiz et al. (2011) 248 0
Shoshani and Slone (2008) 100 200 Excluded participants in experimental
amelioration groups (intervention prior
to media exposure).
Slone (2000) 237 0
Slone and Shoshani (2006) 43 77 Excluded participants in experimental
amelioration groups (intervention prior
to media exposure).
Slone and Shoshani (2008) 84 84 Excluded participants in experimental
amelioration groups (intervention was
post media exposure but Time 2
outcomes recorded after intervention).
Slone and Shoshani (2010) 100 200 Excluded participants in both pre and
post experimental amelioration groups.
Williams and Khan (2011) 40 0
Zeidner et al. (2011) 78 0
31
MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
Table 3
Moderator Analyses
Category g 95% CI Z p k
Intentionality, Q(1) = 2.73, p = .098
Intentional 1.939 [1.289, 2.588] 5.85*.000 14
Unintentional 0.686 [0.650, 2.022] 1.01 .315 3
Pre- or post-September 11, Q(1) = 0.41, p = .523
Pre-September 11 1.134 [-0.490, 2.758] 1.37 .171 2
Post-September 11 1.699 [1.097, 2.301] 5.53*.000 16
Media Format, Q(2) = 5.15, p = .076
Video 2.229 [1.478, 2.979] 5.82*.000 11
Print 0.642 [-0.748, 2.032] 0.91 .366 3
Static images 0.965 [-0.460, 2.390] 1.33 .184 3
Global Location, Q(3) = 36.17, p = .000
USA 0.299 [-0.676, 1.275] 0.60 .548 5
Middle East 4.087 [3.115, 5.060] 8.24*.000 6
Europe/Great Britain 0.744 [-0.167, 1.656] 1.60 .109 6
Australia 0.607 [-1.549, 2.764] 0.55 .591 1
Sensitization, Q(1) = 18.54, p = .000
Yes 2.702 [1.972, 3.432] 7.26*.000 10
No 0.356 [-0.424, 1.136] 0.89 .371 8
Study Design, Q(2) = 40.03, p = .000
Pre-post, no control group 0.556 [-0.875, 1.987] 0.76 .446 2
Random assignment, post only 0.519 [-0.140, 1.178] 1.54 .123 10
Random assignment, pre-post 4.066 [3.147, 4.985] 8.67*.000 6
Note. g = Point estimate of the effect size (Hedges’ g), using the mean of outcomes reported; CI = the 95% lower and
upper limits of g; Z = z test for g, with an asterisk (*) to indicate a statistically significant effect within each category
using a critical level of .05;
k = the number of studies associated with the g value; Q = test statistic which determines whether the effect varies
significantly between the subcategories of the moderator variable (random effects model used).
32
MEDIA EXPOSURE TO LARGE-SCALE VIOLENCE
Table 4
Outcome Type Moderator Analysis with Multiple Outcomes for Some Participants
Category g 95% CI Z p k
Outcome Type (total k = 45), Q(4) = 24.65, p = .000
State anxiety 3.11 [2.368, 3.849] 8.23*.000 12
Negative affect 0.86 [-0.553, 2.263] 1.19 .234 3
Perceived threat 0.60 [-0.162, 1.371] 1.55 .122 10
Other negative outcome 2.27 [1.516, 3.032] 5.88 .000 11
Positive outcome 1.63 [0.805, 2.447] 3.88 .000 9
Note. g = Point estimate of the effect size (Hedges’ g); CI = the 95% lower and upper limits of g; Z = z test for g, with
an asterisk (*) to indicate a statistically significant effect within each category using a critical level of .05;
k = the number of outcomes associated with the g value; Q = test statistic which determines whether the effect varies
significantly between the subcategories of the moderator variable (random effects model used).
* p < .05.
33
