Meta-Analyses on Treatment of PTSD

Journal of Traumatic Stress, Vol. 11, No. 3, 1998
Effects of Psychotherapeutic Treatments for
PTSD: A Meta-Analysis of Controlled Clinical
Jeffrey J. Sherman1,2

This meta-analysis synthesized the results from controlled, clinical trials of psychotherapeutic
treatments for posttraumatic stress disorder (PTSD). Psychotherapeutic
modalities included behavioral, cognitive, and psychodynamic
treatments, in group and individual settings. Participants in the studies included
combat veterans from the Vietnam and Lebanon Wars, crime-related victims,
and severe bereavement sufferers. The impact of psychotherapy on PTSD and
psychiatric symptomatology was significant, d = .52, r = .25, when measured
immediately after treatments were administered. Similarly, there was no decay
in the effect of treatment at follow-up, d = .64, r = .31. Moreover, for target
symptoms of PTSD and general psychological symptoms (intrusion, avoidance,
hyperarousal, anxiety, and depression), effect sizes were significant, ranging
from r's of .2-.49. Results suggest substantial promise for improving psychological
health and decreasing related symptoms for those suffering from PTSD.
KEY WORDS: PTSD; treatment; outcome; control.
Posttraumatic stress disorder (PTSD) affects up to 12% of the U.S.
population (Breslau, Davis, Andreski, & Peterson, 1991; Davidson, Hughes,
Blazer, & George, 1991; Helzer, Robbins, & McEvoy, 1987; Kessler, Sonnega,
Bromet, Hughes, & Nelson, 1995; Resnick, Kilpatrick, Dansky, Saunders,
& Best, 1993), with prevalence estimates varying based on the
methods used for detection of PTSD and the populations sampled (Ameri-
1University of Washington, College of Medicine, Department of Psychiatry and Behavioral
Science, Box 356560, Seattle, Washington 98195-6560.
2Correspondence should be addressed to Jeffrey J. Sherman, c/o Dr. Charles R. Carlson,
Department of Psychology, University of Kentucky, 112 Kastle Hall, Lexington, Kentucky
0894-9867/98/0700-0413$15.00/1 © 1998 International Society for Traumatic Stress Studies
can Psychiatric Association [APA], 1994; Davidson et al., 1996; Friedman,
Schnurr, & McDonagh-Coyle, 1994; Kilpatrick, Saunders, Best, & Von,
1987; Norris, 1992; Resnick et al., 1993). While lower prevalence estimates
are found in studies employing conservative methodologies that focus on
community samples (Helzer et al., 1987), much higher rates are found in
studies focusing on at risk populations such as veterans or motor vehicle
accident or assault victims (Blanchard, Hickling, Taylor, & Loos, 1995;
Breslau et al., 1991; Kilpatrick et al., 1987).
According to the Diagnostic and Statistical Manual of Mental Disorders
(DSM-IV; APA, 1994), criteria for diagnosis require a recognizable
traumatic stimulus followed by episodes of recurrent and intrusive recollections
or feelings, avoidance of stimuli associated with the trauma, and
persistent symptoms of increased arousal. The traumatic stimulus was originally
used for combat-related events, but is now frequently associated with
physical assault, abuse, incarceration, automobile accidents and life threatening
illness (APA, 1994).
The psychological sequelae of traumatic events have been studied for
over 100 years (Putnam, 1881; Salmon, 1919), and a substantial amount of
interest and research has focused on the treatment of these psychological
sequelae. Some of the early treatment outcome research lacked the methodological
rigor and sophistication (Foa & Meadows, 1997, McFarlane,
1994) that is now deemed important for treatment outcome studies. Foa
and Meadows (1997) clearly delineate the criteria for such research, which
include use of reliable and valid measures, unbiased assignment to treatment
conditions, and use of clearly defined target symptoms. In a review
of theoretical and empirical issues facing investigators in the treatment of
PTSD, Fairbank and Nicholson (1987) stated that no controlled studies had
yet appeared in the literature. In 1992, Solomon and colleagues reviewed
pharmacotherapeutic and psychotherapeutic treatments for PTSD and
found six randomized, controlled clinical trials for psychotherapeutic treatments
in the literature. In the last decade, however, there has been a dramatic
increase of interest in the treatment for PTSD and a comparable
increase in controlled treatment studies. For example, a PsycLit search from
January 1974 through March 1996, performed for this review, revealed over
608 published studies containing the key words "PTSD" and "treatment."
Still, only a small percentage of these were randomized controlled clinical
Individual psychotherapy is the most commonly proposed treatment
for PTSD (Fairbank & Nicholson, 1987), and a wide variety of individual
treatments has been advocated. Behavioral interventions such as flooding
or systematic desensitization emphasize the importance of extinguishing the
anxiety associated with intrusive symptoms and reducing avoidant behav-
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iors. Flooding exposes the person either in vivo or imaginally to the aversive
stimuli and thus extinguishes the fear response. In systematic desensitization,
the pairing of relaxation and exposure results in a reciprocal inhibition
of the fear response. Many of these treatments are based on modifications
of Mowrer's (1960) two-factor learning theory as it applies to PTSD
(Boudewyns, 1996; Keane, Zimmering, & Caddell, 1985), where PTSD is
seen as a condition resulting from both classical and instrumental conditioning.
Another exposure-based strategy combines saccadic eye movements
with an exposure component. During eye movement desensitization and
reprocessing (EMDR), patients perform rhythmic, multisaccadic eye movements
while concentrating on their own description of a traumatic memory
(Jensen, 1994; Shapiro, 1989,1991; Silver, Brooks, & Obenchain, 1995; Wilson,
Becker, & Tinker, 1995). While the eye movements distinguish this
strategy, the technique shares many characteristics with desensitization or
flooding (Boudewyns, 1996). Importantly, recent data comparing EMDR
with and without eye movements (Boudewyns & Hyer, 1996; Pitman et al.,
1996) suggested that EMD/R without eye movements, essentially a desensitization
or flooding technique, was equivalent to EMDR with eye movements.
Cognitive behavioral interventions focus on the acquisition and maintenance
of coping skills and on the assumptions and misattributions that
underlie the patient's behavior, expectations, and appraisal of events (Foa
& Rothbaum, 1989; Foa, Rothbaum, Riggs, & Murdock, 1991; Foa,
Steketee, & Rothbaum, 1989). This view suggests that the underlying problem
is not solely anxiety and the maintenance of the fear response, but
that additional difficulties also exist in the overactive cognitive patterns or
schemata that interpret external and internal experiences as dangerous. The
dysfunctional thinking may lead to depression, anxiety, and PTSD (Foa,
Rothbaum, & Steketee, 1993). Therefore, cognitive theory as applied to
the treatment of PTSD (Veronen & Kilpatrick, 1983) focuses on two primary
processes: (1) changing a person's cognitive appraisal of the traumatic
event or changing the process by which an individual attaches meaning to
an event and (2) changing a person's attribution of the event.
Veronen and Kilpatrick (1983) define attribution as the human need
to understand our experiences and continually interpret events and search
for explanations about why things happen. Cognitive therapeutic techniques
help the person identify and correct distorted schemata and attributions
by training the patient to monitor negative thoughts, identify cognitive distortions,
and substitute reality-oriented interpretations (Meichenbaum,
1985). Stress inoculation training (SIT, Foa et al., 1991; Veronen & Kilpatrick,
1983), a widely used stress management technique, focuses on treat-
Meta-Analysis of PTSD 415
ing the anxiety associated with PTSD by teaching coping strategies such as
relaxation training, problem solving, anger control, and self-monitoring
(Meichenbaum, 1985). The goals of SIT focus on increasing patients'
awareness of conditioned stimuli and improving early detection of anxietyprovoking
cues to facilitate the use of coping skills early in the stress response
to reduce anxiety (Litz & Roemer, 1996).
In psychodynamic therapy, the traumatized individual must reconcile
the occurrence of the traumatic event and its meaning with his or her concept
of the self and the world (Horowitz, 1974; Horowitz & Kaltreider,
1980). The patient's response to stress will vacillate between two phases of
denial and intrusive symptoms. Avoidance, denial and emotional numbness
are the results of defensive overcontrol (Horowitz, 1974). When this overcontrol
fails or is overwhelmed, this phase gives way to intrusive thoughts,
flashbacks, or nightmares which are seen as the result of failed defense
mechanisms. The nature of the therapy is dependent on the phase during
which the patient presents. The primary goal of psychodynamic treatment
is integration of the traumatic experience by means of therapeutic reexperiencing
in a supportive environment (Horowitz, 1974). Insight into the
conscious and unconscious meaning of the symptoms can help the patient
master the trauma and restore functioning. The therapist must proceed with
the difficult challenge of developing a therapeutic alliance and handling
transference and countertransference issues (Lindy, 1989). While doing so,
the therapist must recognize that every person brings to any serious life
event his or her own history and existential interpretation of the traumatic
moment (Horowitz, 1977). In treatment, the therapist must consider the
person's self-image, strategies for coping, and defense mechanisms against
intrapsychic and interpersonal threats. The treatment recognizes the influence
of dispositional variables on the response to both the trauma and
therapy. More thorough explanations of these and other treatment strategies
such as group interventions, prevention programs, and anger management
training can be found in additional review and original papers (Allen
& Bloom, 1994; Boudewyns, 1996; Foa et al., 1989; Frueh, Turner, & Beidel,
1995; Shalev, Bonne, & Eth, 1996; Solomon, Gerrity, & Muff, 1992).
When treating a patient suffering from PTSD, the therapist has a variety
of treatment modalities from which to choose, but the absence of a
large and sophisticated outcome literature on PTSD is an important concern
(Fairbank & Nicholson, 1987; Foa & Rothbaum, 1989; Frueh, Turner,
Beidel, Mirabella, & Jones, 1996; McFarlane, 1994). Treatment of PTSD
is a challenge to the therapist because one must attend to and contain
severe distress and suffering. It is particularly difficult to do so if there is
uncertainty about the most appropriate and effective interventions. This
concern has led to an outcry for more work that meets the criteria for
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good outcome research (Foa et al., 1993; McFarlane, 1989,1994; Solomon,
Gerrity et al., 1992). In response, several teams of experimenters have embarked
on and published controlled clinical trials of psychotherapy outcome
for PTSD. Of these and the many noncontrolled studies, a variety of treatments
including behavioral, psychodynamic, and group therapies have been
found to be effective. However, several studies using these treatments report
null findings (Boudewyns & Hyer, 1990; Funari, Piekarski, & Sherwood,
1991; Hyer, Woods, Bruno, & Boudewyns, 1989), or at times,
negative findings where the treatment group worsens in psychological functioning
(Pitman, Altaian, Greenwald, & Longpre, 1991; Solomon, Shalev
et al., 1992).
Several qualitative reviews have been conducted on the PTSD treatment
literature (Boudewyns, 1996; Frueh et al., 1995; McFarlane, 1989,
1994; Shalev et al., 1996; Solomon, Gerrity, et al., 1992), but none have
done so using a meta-analytic approach. Meta-analysis represents a systematic
approach toward integrating findings from a research domain through
statistical analysis of individual studies (Smith & Glass, 1977; Strube &
Hartmann, 1983). The purpose of this article was to review the empirical
evidence for the efficacy of psychotherapeutic treatments for PTSD using
a meta-analytic approach.
Qualitative reviews including case reports, studies without control
groups, and nonrandomized trials concluded that several different types of
treatment protocols reduce both PTSD symptoms and general psychiatric
symptomatology and improve quality of life (McFarlane, 1989, 1994). Recent
reviews on various behavioral, exposure-based strategies (Boudewyns,
1996; Frueh et al., 1995) concluded that these treatments were effective in
reducing typical features of PTSD such as intrusive and avoidant symptoms
and physiological reactivity to stimuli associated with the trauma. After reviewing
five randomized, controlled clinical trials on behavioral treatment
for PTSD, Solomon, Gerrity, et al. (1992) concurred that such strategies
effectively reduced intrusive symptoms indicative of PTSD. Blake (1993)
reviewed eight studies and compared various psychotherapeutic treatments.
This review also concluded that therapies were consistently effective in reducing
the "positive" symptoms of PTSD (i.e., psychophysiological arousal,
intrusive thoughts, nightmares, and anger), but that there was no clear reduction
in "negative" symptoms of PTSD (i.e., numbing, alienation, and
restricted affect).
In contrast, Shalev et al. (1996) reviewed various treatment modalities
and designs including case reports, and controlled and uncontrolled clinical
trials. They concluded that the magnitude of the result was often limited
and that remission was rarely achieved. They also included a framework
for identifying target symptoms and specific treatment modalities that might
Meta-Analysis of PTSD 417
be effectively combined to treat these target symptoms. These authors determined
from their review that a substantial alleviation of suffering did
occur with treatment, but that in controlled studies, the effect size was limited
and that although there was typically alleviation of depression, detachment
and anxiety, there was less of a reduction in the typical symptoms of
PTSD (intrusion, avoidance).
Such questions might be better addressed using a quantitative review
of both overall effects and specific effects on target symptoms such as depression,
anxiety, intrusion, and avoidance. The present study was designed
to answer these questions using meta-analytic techniques to review controlled
treatment outcome studies in which participants received a PTSD diagnosis
and which used objective measures administered before and after treatment
to monitor outcome. This approach made it possible to provide an estimate
of the overall effect size of psychotherapeutic treatments and to determine
the efficacy of these treatments for ameliorating specific symptoms.
Identification of Studies
The major sources for identifying the empirical studies used for the
meta-analysis were computerized databases including Psyclit, ERIC,
Medline, Cinahl Nursing Database, Dissertation Abstracts, and the PILOTS
Traumatic Stress Database from Dartmouth College. These were
searched using the following keywords and combinations of keywords:
"posttraumatic stress disorder," "PTSD," "therapy," "treatment," "outcome,"
and "control." Reference lists from existing reviews and empirical
studies were also consulted. One criticism of meta-analytic techniques is a
bias toward analyzing only significant, published findings. Tb include such
"fugitive literature" (Rosenthal, 1995, p. 184), attempts were made to include
unpublished studies in the meta-analysis by contacting 25 authors in
the field and requesting any unpublished work. Replies via e-mail, U.S.
mail, or telephone from 13 of these authors resulted in receipt of seven
additional studies, two of which were included in the analysis (Boudewyns
& Hyer, 1996; Foa, Freund et al., 1994).
Inclusion Criteria
Only clinical trials performed predominantly on participants who met
threshold DSM-III, III-R, or IV criteria for PTSD were included in the
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meta-analysis. Analyses were also restricted to studies that used a comparison
group, provided inferential statistics with which to calculate relevant
effects sizes, and which used objective measures of outcome taken before
and after treatment. Eleven studies included participants meeting the criteria
based on combat-related events, and six studies included participants
meeting the criteria based on noncombat-related trauma (crime-related or
bereavement). The meta-analysis did not include studies on general care
or counseling programs for victimized or traumatized people unless the participants
met criteria for PTSD.
Coding System
All studies were coded based on the following criteria: (a) author, year
of study, (b) total N, (c) type of participants (combat veteran vs. noncombat),
(d) type of intervention vs. type of control, (e) design and measures
used to calculate effect sizes at posttreatment and follow-up, and (f) length
of follow-up.
Two strategies were used for comparing effect sizes across the studies.
First, effect sizes were averaged across all dependent measures for each
study. These "supervariables" (Rosenthal, 1984, p. 36) were weighted
equally in determination of an overall effect for all of the studies. One
advantage of averaging a single effect size is that it avoids spurious inflation
of effect sizes from studies in which a number of dependent measures are
used. A second advantage is that it provides a measure of overall change
across several PTSD symptom categories, social functioning, and psychological
adjustment. One disadvantage, however, is that given the multidimensional
nature of PTSD, aggregating a single effect size based on these
symptom clusters and social functioning results in the loss of a theoretically
meaningful outcome. Thus, a supplementary strategy was adopted in order
to provide a more specific measure of treatment outcome. Similar to methods
used by Wolraich, Wilson, and White (1995), dependent measures were
categorized for target symptoms relevant to the disorder (i.e., intrusion,
avoidance, arousal, depression, and anxiety). When the data were available,
effect sizes were then calculated from the available studies based on these
target symptoms.
Meta-Analysis of PTSD 419
Type of Dependent Variables
Effect sizes were calculated for a composite effect from each study.
This effect combined all of the dependent measures evaluated in each
study. In addition, five categories of dependent measures were developed
and effect sizes were estimated for each symptom category. The intrusion
category included measures from the PTSD Structured Interview (SIPTSD;
Davidson, et al., 1989), the intrusion scale of the Impact of Event
Scale (IBS; Horowitz et al., 1979), clinical interviewer ratings of intrusive
experiences, the sleep disturbances subscale of the Modified Vietnam Experiences
Questionnaire (MVEQ; Cooper & Clum, 1989), and other selfreports
of nightmares or flashbacks. The hyperarousal category included
self-reports, interviewer ratings and/or psychophysiological test results of
arousal, anxiety, EMG activity, heart rate, and skin conductance in response
to stressful images. This category also included scores on the arousal
subscale of the PTSD Symptom Scale (PSS; Foa et al., 1993). The avoidance
category included interviewer ratings of avoidance and scores on the
avoidance subscales of the PSS and IES. The depression category included
scores from the Hamilton Rating Scale for Depression (Hamilton, 1960),
Beck Depression Inventory (BDI; Beck et al., 1961), and the depression
subscale of the Symptom Checklist 90-Revised (SCL-90-R; Derogatis,
1977). The anxiety category included scores from the state version of the
State-Trait Anxiety Inventory (STAI; Spielberger, Gorsuch, & Luschene,
1970) and the anxiety subscale of the SCL-90-R.
While none of the studies in the meta-analysis made any claims that
long-term personality change would occur with treatment, two studies
(Brom, Kleber, & Defares, 1989; Keane, Fairbank, Caddell, & Zimering,
1989) included global measures of personality functioning. Brom, et al.
(1989) stated that these data were reported only because of significant, but
not predicted change on several subscales. Since the intent of few PTSD
treatments is global personality change, and since this study does not seek
to evaluate such change, neither global personality nor trait measures are
included in the analyses. Subscales on the MMPI or other personality measures
are not included as dependent measures unless specifically associated
with PTSD (i.e., PTSD subscale of the MMPI).
Calculation of Effect Sizes
When the data were available, effect sizes were calculated for treatment
effects immediately after treatment (post) and from 3 months to 2
years after treatment (follow-up). If means and standard deviations were
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available for treatment and no-treatment control conditions, effect sizes
were calculated by subtracting the treatment group mean from the no treatment
or control group mean and dividing the result by the pooled standard
deviation (Glass, McGaw, & Smith, 1981; Johnson, 1989). When insufficient
information was supplied for calculating the effect size in such a way,
i.e., differences reported in terms of nonparametric tests, t statistics or F
statistics formulas applied by Johnson (1989) were used to obtain estimates
of the effect size (ES). When results were reported as nonsignificant and
insufficient data were reported to calculate an ES, the ES was conservatively
estimated as an effect size of 0. Only studies providing comparisons
between treatment and control groups were used to estimate the post treatment
effect size. At follow-up, effect sizes were estimated for studies providing
either comparisons between treatment and control conditions or
between pre-treatment and follow-up periods for a treatment group.
On some measures, a negative treatment-control difference reflected
that treatment improved patient status by reducing symptoms (i.e., lower
intrusion or avoidance scores for treatment group). On other measures, a
positive treatment-control condition reflected that treatment improved psychosocial
functioning (e.g., increased self-efficacy). Therefore, the direction
of effect was standardized across effect sizes so that positive effects indicated
a desirable effect of treatment, and negative effects indicated an undesirable
effect of treatment.
The effect size calculated was g, defined as the difference between the
means of the intervention and comparison group, divided by the pooled
standard deviation (Cohen, 1977; Johnson, 1989). The g's were converted
to d's by correcting them for bias (i.e., g's may overestimate the population
effect size for small samples) (Johnson, 1989). For convenience, effect sizes
are expressed as both d's and r's. Finally, a homogeneity statistic, Q, was
used to determine whether the effect sizes were consistent across all studies
(Hedges & Olkin, 1985; Johnson, 1989).
Table 1 presents the study characteristics and effect sizes for each
study. The combined sample represents 690 participants from 17 studies.
Of these, 11 studies used a total of 281 Vietnam veterans and 81 Israeli
combat veterans from the Lebanon war, four studies used 180 female
rape/assault victims, and two studies (Brom et al., 1989; Vaughan et al.,
1994) used 148 subjects (111 females) who were victims of violent crimes,
motor vehicle accidents (MVA), child abuse, or suffered PTSD from the
traumatic loss of a loved one.
Meta-Analysis of PTSD 421
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Meta-Analysis of PTSD 423
The predominant treatment modality in the studies was behavioral or
cognitive behavioral. In addition to a cognitive behavioral treatment, one
study (Brom et al, 1989) used psychodynamic and hypnotherapy. Less traditional
treatments included the Koach program (Solomon, Shalev et al.,
1992), anger treatment (Chemtob, Novaco, Hamada, & Gross, 1997),
EMDR (Boudewyns & Hyer, 1996; Jensen, 1994; Vaughan et al., 1994),
adventure-based activities and psychodrama (Ragsdale, Cox, Finn, & Eisler,
1996), and the Coatesville PTSD treatment program (Hammarberg & Silver,
The Koach program was a month-long residential treatment program
that included self-help groups, milieu therapy, family therapy, supportive
counseling, cognitive behavioral education groups, relaxation and in vivo
desensitization. Desensitization included living in tents, wearing military
uniforms, military combat and weapons training, mountain climbing, and
other military exercises throughout the treatment period. In addition to
routine care, participants in the Chemtob et al. (1997) study received manual-
guided individual psychotherapy sessions for anger management. Sessions
focused on anger self-monitoring exercises, relaxation, cognitive
restructuring of anger by modifying appraisals or altering attentional focus,
training in behavioral coping, assertiveness, and communication skills, and
role-playing devised to arouse anger. Ragsdale et al. (1996) treated patients
with a 26-day inpatient program. Patients engaged in activities designed to
increase trust by requiring mutual cooperation such as traversing a 12-ft
wall and falling backwards off of a platform to be caught by other group
members. Group sessions involved PTSD education, grief work, processing
experiences during the adventure-based activities, and psychodrama, a
reenactment through role play of the original traumatic event, Hammarberg
& Silver (1994) treated veterans in a 90-day inpatient, PTSD treatment
program, using multiple treatment modalities. Treatments were usually in
a group format and consisted of patient education, relaxation training,
dreamwork, and peer groups that were run without therapist assistance.
The effect sizes displayed in Table 1 represent an average effect size
for each study across all the dependent measures and for each type of treatment
modality, within each study. Thus, this composite effect represents
the extent to which treatment contributes to eliminating PTSD, reducing
PTSD symptoms (intrusion, avoidance, hyperarousal), and reducing psychiatric
symptomatology (depression, anxiety). These effect sizes are displayed
on the right side of Table 1 at posttreatment (immediately after treatment
for all studies) and at the first follow-up for each study. The effect sizes
immediately after treatment ranged from to .03 to 8.4. The overall effect
was significant, d = .54, r = .26, with a non-zero, 95% confidence interval
suggesting that the true effect lies between .39 and .68. One study (Penis-
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ton, 1986) contributed to a significant test of heterogeneity, Qw(23) =
37.24, p < .05. Following the methods of Hedges and Olkin (1985), that
study was removed from further analysis. With this outlier removed, the
overall effect was significant, d = .52, r = .25, with a 95% confidence interval
between .37 and .67. The effect sizes for the remaining studies were
homogeneous, Qw(22) = 11.94,p = .96. This suggests that the mean from
the effect sizes can be presumed to estimate a single underlying population
effect size.
Twelve studies provided data for follow-up occurring between 3 months
and 2 years after the end of treatment (Table 1). The effect sizes at the
first follow-up period ranged from -.25 to +1.69. The overall effect was
significant, d = .53, r = .25, with a non-zero, 95% confidence interval suggesting
that the true effect lies between .37 and .69. One study (Solomon,
Shalev et al., 1992) contributed to a significant test of homogeneity, Qw(\8)
= 36.61, p < .05. With this outlier removed, the overall effect was significant,
d = .64, r = .31, with a 95% confidence interval between .47 and
.81. The effect sizes for the remaining studies were homogeneous, Qw(17)
= 22.59, p = .21.
The effect sizes presented in Table 2 represent the effect of psychotherapy
treatment on specific target symptoms. The effect sizes immediately
after treatment ranged from .53 for anxiety to .79 for avoidance symptoms.
All effect sizes are significant and nonzero and are presented after correction
for heterogeneity. The only effect size with significant variability
(-.15-+8.4) was hyperarousal. This variability may reflect the wide variety
of assessment techniques used to assess hyperarousal such as EMG, HR,
SCL, SUDS, and self-reports.
The overall effect, d = .52; r = .25, achieved from examination of the
17 studies (690 participants) demonstrates strong empirical support for the
Meta-Analysis of PTSD 425
Table 2. Effect Sizes Across Treatments by Target Variables
No. of
No. of
efficacy of psychotherapeutic interventions for the treatment of combat,
crime, and traumatic bereavement-related PTSD. This indicates that psychotherapeutic
treatments have positive effects on characteristic PTSD
symptoms and symptoms of depression and anxiety. In order to put magnitudes
of effect size into perspective, Cohen (1977) provided guidelines
for interpretations of effect sizes and defined conventional magnitudes corresponding
to small (r = .1), medium (r = .3), and large (r = .5) effect
sizes. From this perspective, an r of .25 corresponds to a moderate correlation
between treatment and outcome. Similarly, this effect size reflects
an improvement in the treatment group of over one-half of a standard deviation
greater than that for the comparison group. Further, these effect
sizes were relatively consistent across the studies reviewed. This is likely
due to the similarity in research design between the controlled treatment
outcome studies used in the analysis.
While the effect sizes observed in this study are consistent with other
studies of psychotherapy outcome (Clum, Clum, & Surls, 1993; Hunter &
Schmidt, 1990; Smith & Glass, 1977), it is also important to evaluate the
practical usefulness and clinical utility of such an effect. Rosenthal (1984)
recommends using the binomial effect size display (BESD) for an intuitively
appealing interpretation of an average effect. The BESD represents an effect
size in terms of overall success rate for the treatment group. The BESD
can be interpreted as the estimated difference in success probability between
the treatment and control groups. Thus, a correlation coefficient of
.25 corresponds to increasing a success rate from 38% to 62% by means
of an intervention (Rosenthal, 1984; Wolfe & Cornell, 1986). This means
that the expected improvement rate for the psychotherapy condition was
62%, in contrast to an expected improvement rate of 38% for the nonintervention
group. A large proportion of the subjects used in the examined
studies were inpatients diagnosed with chronic PTSD. Considering the debilitating
nature of PTSD, the severity of symptoms endorsed by subjects
prior to participating in the studies, and the chronic course of PTSD, this
change in functioning is clinically significant and represents important practical
usefulness for psychotherapeutic treatment.
This meta-analysis also addressed some specific questions about the
treatment of PTSD. Shalev et al. (1996) stated that the magnitude of the
results in PTSD treatments are often limited, that remission is rarely
achieved, and that there is typically alleviation of depression, detachment
and anxiety, but less of a reduction in the typical symptoms of PTSD (intrusion
and avoidance). In contrast, these results suggest that the magnitude
of improvement due to psychotherapeutic treatments is moderate and
that these treatments are effective in reducing PTSD symptoms, depression,
and anxiety. Moreover, an analysis of effect sizes at follow-up suggests that
426 Sherman
these treatment effects are maintained even after discontinuation of treatment.
Further, six of the studies reviewed in the meta-analysis assessed patients
for diagnosis of PTSD after treatment and provided the necessary
data to compute percentage remission. Of the 103 patients with a full PTSD
diagnosis before treatment, 43% (44) improved to such a degree that they
did not meet diagnostic criteria after treatment. Considering the chronic
nature and severity of the disorder and the relative brevity of many of these
treatments, we would interpret this as a considerable percentage of subjects
who achieved improvement and remission. Finally, the meta-analysis of
treatment effects for specific symptoms was also revealing. Results of the
current review suggest that psychotherapeutic treatment was indeed effective
in reducing symptoms of depression and anxiety. Treatment was also
effective in reducing target symptoms of PTSD such as intrusion, arousal,
and avoidance. While treatment effects for all symptom categories were
significant, the greatest treatment effects were found for the intrusion and
avoidance categories of target symptoms.
While the results from this review lead to somewhat different conclusions
from those of Shalev et al. (1996), they are more consistent with conclusions
from other reviews that find that treatment effectively reduces the
hallmark symptoms of PTSD (Blake, 1993; Frueh et al., 1995; Solomon,
Gerrity et al., 1992). The present review focused only on controlled clinical
trials that adhered to a somewhat rigorous inclusion criteria. As such, this
review may have been more similar to the review by Solomon, Gerrity et
al. (1992) that focused only on randomized and controlled clinical trials.
All six studies reviewed in their report involved some form of exposure. In
contrast, the review by Shalev and colleagues provides an excellent and
broad overview of treatments for PTSD, but it includes studies of more
variable quality such as case reports, controlled and open trials. Moreover,
their review represents a broader array of treatment modalities (behavioral,
cognitive, psychodynamic, group, hypnosis, rehabilitation) in an outpatient
and inpatient environment than either the present or other reviews
(Boudewyns, 1996; Frueh et al., 1995; Solomon, Gerrity et al., 1992).
This review included published and unpublished studies on various
treatments of PTSD. However, the modality with the greatest representation
is the use of exposure techniques in a behavioral or cognitive
behavioral treatment setting. In fact, all but two studies used some form
of exposure technique (flooding, desensitization, implosion, EMDR, psychodrama)
with or without relaxation training. Thus, consistent with other
data (Boudewyns, 1996, Foa & Rothbaum, 1989; Frueh et al., 1995; Litz
& Roemer, 1996; Solomon, Gerrity et al., 1992), findings lend general support
for exposure-based therapies as effective treatment for both combat
and noncombat-related PTSD.
Mete-Analysis of PTSD 427
One study (Brom et al., 1989) included treatment groups receiving
either trauma desensitization, hypnotherapy, or psychodynamic therapy.
Foa et al. (1991, 1994) included treatment groups receiving stress inoculation
training, prolonged exposure, supportive counseling or a combination
of prolonged exposure and stress inoculation training. Two studies
(Boudewyns & Hyer, 1996; Vaughan et al., 1994) compared EMDR to
other forms of exposure or muscle relaxation therapy. If more controlled
studies had been available that compared a variety of treatments, a more
detailed analysis could have compared these treatments. Nevertheless, the
data from the Foa et al. (1991, 1994) studies suggest that effect sizes for
supportive counseling are lower than effect sizes for exposure therapies.
The data from the Brom et al. (1989) study suggest that hypnotherapy and
psychodynamic therapy are comparable to exposure therapy, and the data
from the Boudewyns and Hyer (1996) study suggest that effects from
EMDR are comparable to exposure therapy. In contrast, the data from
Vaughan et al. (1994) suggest that EMDR was superior to either an image
habituation treatment or a muscle relaxation treatment. This is consistent
with other research groups who have failed to find reliable differences between
therapeutic modalities for the treatment of PTSD (Frank et al., 1988;
Frank & Stewart, 1983, 1984).
A review of the treatment modalities most commonly used in the
treatment of PTSD suggests that all treatment approaches share a number
of common elements (McFarlane, 1994). All treatments share a primary
aim to help the patient develop a realistic appraisal of the threat experienced
during the trauma. All treatments seek to help the patient overcome
the cognitive and behavioral avoidance of internal cues and external reminders
of the trauma. All treatments also seek to assist individuals to work
through the meaning of their traumatic experience and to gain a sense of
mastery over their intrusive recollections. In one form or another, all treatments
focus on Horowitz' (1974) conceptualization suggesting that the goal
of psychotherapy is to help the patient work through the trauma experience
through gradual reexposure of the actual traumatic event and reinterpretation
of its meaning. Thus, while exposure-based techniques clearly have
the greatest representation when reviewing the literature on controlled trials,
many treatment modalities may have similar active therapeutic components.
This review and others (Shalev et al., 1996) call into question the efficacy
of using in vivo exposure-based techniques without sufficient patientbased
control of the exposure situation and therapeutic support. One
controlled, clinical trial reviewed in this article (Solomon, Shalev et al.,
1992) involved a residential treatment of 4 weeks exposure to military cues
including living in tents, wearing uniforms, mountain climbing, weapons,
428 Sherman
artillery, and hand-to-hand combat training for Lebanon War veterans.
Treated patients experienced considerable deterioration for up to 9 months
posttreatment. Similarly, Scurfield, Wong, and Zeerocah (1992) exposed
war veterans to helicopter rides and found increases in intrusive and painful
memories. While this study provided intense exposure, it may not have provided
sufficiently broad exposure to the full-range symptom-provoking cues.
In contrast, Richards, Lovell, and Marks (1994) found improvement with
a behavioral treatment program that included live exposure but also included
imaginal exposure. These results suggest the exercise of considerable
caution in the use of in vivo techniques for the treatment of PTSD.
One limitation of the study is that although the finding of significant
impact of treatments for PTSD is encouraging, this finding cannot be used
as full support for any single theoretical, therapeutic rationale. While most
of the studies used an exposure and/or relaxation technique, results for
alternative treatments were similar to those for the more traditional cognitive
behavioral techniques. Another concern is that eight studies in the
analysis used wait-list, no-treatment control groups, rather than a psychological
placebo control group. Since McConaghy (1990) demonstrated that
placebo treatments show superior outcomes to wait-list controls, it is possible
that the effect from studies using a wait-list control may be inflated.
Further, it is possible that the improvement outcomes in the treatment
groups could be due to nonspecific effects of therapy. On the other hand,
nine studies used control groups receiving standard, routine-care treatments
such as supportive counseling and individual and group therapy. Results
suggest that even when compared to control groups receiving standard care,
additional treatment is beneficial. As such, using active, psychological placebo
groups in future treatment studies would seem appropriate.
An important concern, especially with the limited number of studies
used in this analysis, is whether the combined effect sizes presented here
represent all of the research on this topic, including unpublished studies.
In an attempt to address this limitation, 25 authors in the field were contacted
in the hopes of gaining any unpublished work. These requests resulted
in seven responses and two studies that qualified for inclusion in
these analyses. In addition, in order to account for this "file-drawer" problem,
methods from Rosenthal (1979) were used to estimate the number of
new, filed, or unretrieved studies that would be required to bring the results
to nonsignificance. An estimated 57 nonsignificant studies would be required
to reduce the overall effect size to nonsignificance.
Certain treatment modalities were underrepresented or not represented
in this meta-analysis such as psychological debriefing after trauma
(Raphael, Meldrum, & McFarlane, 1996), anger management (Chemtob,
Hamada, Roitblat, & Muraoka, 1994; Gerlock, 1994), and treatment of
Meta-Analysis of PTSD 429
traumatized children (McNeil & Todd, 1986; Saigh, 1986, 1987a, 1987b).
This limitation reflects a dearth of controlled, clinical trials in these important
areas. For example, Raphael and colleagues (1996) discuss the merits
of debriefing programs in the prevention of PTSD and call for
randomized controlled trials in this area. Similarly, the present literature
review for this study and prior reviews (Boudewyns, 1996) found no controlled
treatment studies on children with PTSD, although children clearly
suffer from the disorder and may be particularly vulnerable (Boudewyns,
1996; Lyons, 1987). Further, results from the one study on anger management
(Chemtob et al., 1997), although based on a small sample, are quite
promising and suggest the need for continued study in this area. The current
and other reviews elucidate the need for more controlled trials in these
Miller, Kamenchenko, & Krasniasnski (1992) emphasize the importance
of making a clear differentiation with respect to the processing and
impact of traumas from man-made vs. natural traumas, physical vs. psychological
traumas, and traumas associated with domestic violence. Another
limitation to this meta-analysis is that we combined studies on PTSD
sufferers due to a variety of etiological traumas (war, crime, motor vehicle
accident, bereavement). While we recognize the potential limitations in aggregating
results across different types of traumatic experiences, insufficient
sample size precluded an analysis of type of etiology as a moderator variable.
It is important to note, however, that regardless of etiology, psychotherapeutic
treatments had similar efficacies.
This study reviewed and quantitatively synthesized results of psychotherapeutic
treatment modalities for the treatment of PTSD. The effect
sizes observed in this review were significant and encouraging. Psychotherapeutic
treatment reduces PTSD, and general psychiatric symptomatology,
and these effects are maintained even after termination of treatment. The
data support the continued use and investigation of psychotherapeutic modalities
for the treatment of PTSD.
I am very grateful to Drs. Judith Lyons, Thomas Miller, Charles
Carlson, James McCubbin, John Wilson and Jeffrey Okeson for their assistance
and reviews of earlier versions of this article. I thank Dr. Bryan
430 Sherman
Johnstone for his technical assistance and helpful discussions about metaanalytic
issues. I also thank three anonymous reviewers and the editor for
their very helpful comments and recommendations.
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