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A BRIEF REVIEW OF ISSUES IN PTSD 
RESEARCH FOLLOWING THE SEPTEMBER 11 
TRAGEDIES

The attacks on the World Trade Center (WTC) on September 11, 2001 
resulted in the largest loss of life due to terrorism that the United States 
has ever encountered. Terrorism often results in pronounced numbers 
of Post Traumatic Stress Disorder (PTSD) cases. Following the Sep-
tember 11 attacks, many research studies reported increases in PTSD, 
Post Traumatic Stress Symptoms (PTSS), and stress reactions; however, 
the inconsistency in the methods used to gather and analyze data poses 
problems in comparing and interpreting these results. A brief review of 
the methods used in trauma-related research following September 11 is 
presented. Guidelines for interpreting this research are also presented. 

The attacks on the World Trade Center (WTC) on September 11, 2001 
were devastating, killing 2,797 people (American Red Cross, 2003). 

Concerns over widespread trauma both nationally and internationally have 
been at the forefront of the mental health agenda since that time. Ongoing re-
search regarding the short- and long-term effects of traumatic events is crucial 
for evidence-based social work practice and the provision of mental health 
services. However, a critical analysis of the methodologies used in research 
studies is needed before conclusions regarding the prevalence of Post Trau-
matic Stress Disorder (PTSD) or other mental health outcomes can be made. 

Currently no common methodology for studying reactions to wide-scale 
disasters exists, making it difficult to compare studies and establish the valid-
ity of research results (North & Pfefferbaum, 2002). In this paper, the use and 
interpretation of trauma questionnaires as well as the terminology used in de-
scribing PTSD symptomatology will be explored so that researchers and cli-
nicians alike may be more informed consumers of trauma-related literature. 

Social workers, other mental health professionals, and researchers 
need to be able to differentially identify and properly diagnose PTSD. 
In the first two weeks of the World Trade Center Health Registry, more 
than 10,000 people worldwide enrolled for assessment through a health 
survey gauging the mental and physical health problems resulting from 
the September 11 attacks (New York City Department of Health and Men-
tal Hygiene, 2001). This response indicated the large number of persons 
impacted by the disaster. The American Red Cross (2003) reports that 

Sarah S. Jeon & Terra K. Marroquin 

A Brief Review of Issues in PTSD Research

Journal of Student Social Work, Volume II   17



their organization provided as many as 240,000 mental health contacts 
immediately following the attacks. It was critical, therefore, that mental 
health professionals were able to identify persons who were likely to de-
velop PTSD so as to offer appropriate treatment to these large populations. 

Diagnosing PTSD
According to The Diagnostic and Statistical Manual of Mental Dis-

orders, Fourth Edition, Text Revision (American Psychiatric Association 
[APA], 2000), a diagnosis of PTSD is dependent upon exposure to an event 
that involves “actual or threatened death or serious injury” to one’s self or 
loved one or the witnessing of such an event which causes a sense of “intense 
fear, helplessness, or horror” (APA, p. 464). Symptoms, including re-expe-
riencing the event, avoidance and numbing, and increased arousal, must last 
longer than one month and cause significant impairment or distress. Fre-
quently, following a traumatic event an individual may not meet criteria for 
PTSD but may have Acute Stress Disorder (ASD) or Post-Traumatic Stress 
Symptoms (PTSS). ASD symptomatology matches that of PTSD but occurs 
within 30 days of a traumatic event (APA, 2000). People suffering from PTSS 
may have some characteristics of ASD or PTSD and may experience signif-
icant distress, yet do not meet full DSM-IV-TR criteria for either disorder. 

While practitioners must carefully adhere to DSM-IV-TR criteria to 
diagnose PTSD, prevalence studies following mass trauma like the events 
of September 11 are rarely able to draw diagnostic conclusions. Using a 
clinical interview, a clinician can conduct a thorough assessment by gather-
ing information on the duration and extent of the impairment, gauging the 
client’s prior history of trauma and psychiatric illness, and assessing for 
co-morbidity of other psychiatric illnesses. Researchers use brief question-
naires like the PTSD Checklist (PCL) (Weathers, Litz, Herman, Huska & 
Keane, 1993) to make statements about the prevalence of PTSD symptoms. 
Although such checklists are the most efficient way to uniformly collect 
data from large samples, they do not measure impairment of functioning 
or duration of symptoms, which are crucial for a DSM-IV-TR diagnosis. 
Research studies often do not conduct thorough assessments, and, when 
misrepresented or misinterpreted, may lead to inflated statistics about the 
true number of PTSD cases. Increasing the knowledge base concerning the 
data collection, analysis, and interpretation methods used in trauma research 
is necessary to provide a clearer picture of prevalence rates, responses to 
traumatic events, and the design of effective interventions for practitioners.

Trauma, Terrorism, and PTSD Research
Prior to September 11, the National Institute of Mental Health (2001) 

reported that 3.6% of adults in the United States (5.2 million people) had 
PTSD during a given year. While many of the studies of the psychological 

Jeon & Marroquin 

18   Journal of Student Social Work, Volume II



impact of trauma due to terrorism in the United States were conducted on 
individuals exposed to the Oklahoma City Bombing (North et al., 1999), 
more recent studies of terrorism and PTSD in the United States focus on 
September 11. Several of these studies reported a surge in PTSD-related 
symptoms amongst persons living in New York City following the at-
tacks (Bascarino, Galea, Ahern, Resnick, & Vlahov, 2002; Sattler, 2002; 
Schlenger et al., 2002; Schuster et al., 2001). Galea et al. (2002) found 
that 7.5% of a sample of adults living south of 110th Street in Manhat-
tan showed symptoms consistent with PTSD. South of Canal Street, the 
prevalence rate was reportedly 20%. Schlenger et al. estimated that there 
could be more than 500,000 cases of PTSD as a result of the event in the 
New York metropolitan area alone and reported a rate of 11.2% of prob-
able PTSD cases found in their study of New York City residents. Such 
results, however, must be considered carefully given that the methods 
used to interpret findings of PTSD symptoms vary from study to study. 

The events of September 11 were distinct in nature due to both the 
large-scale destruction akin to a natural disaster and the component of inten-
tional harm inflicted by one human towards another. Natural disasters have 
traumatic effects due to large losses of life and property (Cao, McFarlane, & 
Klimidis, 2003). However, it has been found that intentional harm inflicted 
by one human towards another has even longer-lasting effects in the de-
velopment of PTSD (Breslau, Chilcoat, Kessler, Peterson, & Lucia, 1999; 
Norris, Byrne, Eolia, & Krzysztof, 2001; Thabet, Abed, & Vostanis, 2002). 

According to the Code of Federal Regulations (as cited in the Federal 
Bureau of Investigations, 1998), terrorism is defined as “…the unlawful use 
of force and violence against persons or property to intimidate or coerce a 
government, the civilian population, or any segment thereof, in furtherance 
of political or social objectives.” Terrorism, as viewed from a mental health 
perspective, is particularly damaging and has resulted in a pronounced 
number of cases of PTSD (Bleich, Gelkopf, & Solomon, 2003; North et 
al., 1999; Schlenger et al., 2002). Additionally, a single-event terrorist at-
tack such as September 11 may be as traumatic as repeated exposure. Ble-
ich, Gelkopf, and Solomon conducted a study on a representative sample 
of the population in Israel, a country where frequent terrorist acts occur, 
and found that 9.4% of Israeli individuals met symptom criteria for PTSD 
(Bleich, Gelkopf, & Solomon). This is comparable to 7.4% (Galea et al., 
2002) and 11.2% (Schlenger et al.) found in New York City following the 
September 11 attacks. These results are noteworthy considering that much 
of the sample gathered in Israel had experienced 19 months of repeated 
terrorist attacks prior to their study. However, the methodologies used for 
each of these studies were different, as were the sources of exposure consid-
ered, the subjects’ proximity to the events, and the sampling methods used.

Journal of Student Social Work, Volume II   19

A Brief Review of Issues in PTSD Research



Approaches to Research
The inconsistent application of questionnaires to conduct research 

on the prevalence of PTSD poses problems in comparing and validating 
results of research studies. Most studies utilize one of two major PTSD 
scales—the PCL or the Diagnostic Interview Schedule (DIS), which is 
based on the DSM-III-R (APA, 1987). Although comparisons between the 
two instruments are difficult to draw, the more distressing issue is the lack 
of consistency in interpreting results from the same measure. Three dif-
ferent methods noted in major studies of PTSD following the September 
11 attacks illustrate this point. In the studies reviewed here, Schuster et al. 
(2001) opted to present PTSD symptoms according to levels of symptom 
severity; Schlenger et al. (2002) portrayed “probable PTSD” as a dichoto-
mous variable, in which an individual met criteria through the tallying of 
symptoms; and Galea et al. (2002) grouped symptoms according to DSM-
IV-TR criteria and determined whether the person met threshold numbers 
in each category. While these methods are useful as screening devices 
for potential PTSD cases, they can lead to inflated prevalence statistics. 

Researchers who conduct large prevalence studies usually un-
derstand the inherent difficulties in diagnosing PTSD through scales 
and brief measures, rarely stating outright that they are measur-
ing PTSD. Instead, they employ tentative language, carefully choos-
ing their words to reflect the uncertainty of a clinical diagnosis. Below, 
the language used in each  research study reviewed will be examined.  

Levels of Symptom Severity
One of the largest studies conducted after September 11 was by Schus-

ter et al. (2001) and has been cited extensively (Bleich, Gelkopf, & Solo-
mon, 2003; North & Pfefferbaum, 2002; Schlenger et al., 2002). In this 
study, 560 adults participated in telephone interviews three to five days 
after September 11 that focused on their stress and coping responses. The 
researchers used the term “stress reactions” throughout their article. This 
careful use of terminology reflects the fact that PTSD cannot be diagnosed 
for at least one month after the event. Although assessing for stress re-
actions provides a measure of general distress, it does not discern which 
reactions are sufficient for a full DSM-IV-TR diagnosis of PTSD. The 
term “stress reactions” also seems to appropriately indicate that the use of 
cutoff scores for PTSD symptoms does not necessarily mean that the per-
son meets a full DSM-IV-TR diagnosis of PTSD (North & Pfefferbaum).

Schuster et al. (2001) used the PTSD Checklist (PCL) to determine lev-
els of symptom severity. The PCL is a 17-item checklist directly based on 
PTSD symptoms listed in the DSM-IV-TR. It was initially tested on combat 
veterans, and then adapted for civilians (PCL-C). It has been tested on vic-

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20   Journal of Student Social Work, Volume II



A Brief Review of Issues in PTSD Research

tims of non-combat and non-assaultive traumas (Blanchard, Jones-Alexan-
der, Buckley & Forneris, 1996). Based on participant responses to the PCL’s 
5-point Likert scale, Schuster et al. reported that 44% of respondents had at 
least one substantial stress symptom (a rating of 4 or higher), 68% had one 
symptom “moderately” (3 on the Likert scale), and 90% had at least one 
symptom “a little bit.” Their claim that a high percentage of respondents 
demonstrate stress symptoms “a little bit” may be misleading when based 
on a mark of two on a five-point scale. Likert scales offer an ordinal level 
of measurement without guidance as to the distinction between the choices. 
In addition, this method of classifying PTSD symptoms is based on the self-
report of the individual of his/her apparent symptoms. The choices made 
are completely subjective, since one cannot know how each individual in-
terprets his/her symptoms or what the distinction between a rating of 2 or a 
rating of 3, for example, means to each participant. In addition, as Schuster 
et al. note, though baseline measures exist for PTSD prevalence rates, none 
are available for stress symptoms. Having “a little bit” of insomnia, or in-
creased physiological arousal could easily have been pre-existing and incor-
rectly attributed to September 11. Hence, it is not possible to objectively de-
termine the effects of September 11 on PTSD or PTSS through this method. 

The Tallying of Symptoms
Some researchers have tallied symptoms to derive a diagnosis of PTSD 

or “probable PTSD” (Schlenger et al., 2002; Simeon, Greenberg, Knutelska, 
Schmeidler, & Hollander, 2003). Schlenger et al. based this procedure on a 
report by Weathers, Litz, Herman, Huska, and Keane (1993) who state that a 
PCL cutoff score totaling 50 or greater has strong diagnostic utility for PTSD. 
This has encouraged the use of the PCL in PTSD research studies. However, 
Schlenger et al., in agreement with North and Pfefferbaum (2002), are care-
ful to note that only clinical assessments can definitively diagnose PTSD. 
Schlenger et al. use the phrase “probable PTSD” to discuss their findings. 
Furthermore, it has been appropriately recommended that the PCL be used 
only as a screening device (Blanchard, Jones-Alexander, Buckley, & For-
neris, 1996). Although the PCL is efficient for data collection and has good 
diagnostic utility, it does not measure the duration and impairment criteria, 
which are crucial for a clinical diagnosis (North & Pfefferbaum). In addition, 
tallying alone fails to determine whether each individual meets the threshold 
requirements for each symptom cluster, according to DSM-IV-TR criteria. 

DSM-IV TR Symptom Clusters
The DSM-IV-TR (APA, 2000) criteria for PTSD include three symp-

tom clusters (B, C, and D) in addition to the requirements for exposure 

Journal of Student Social Work, Volume II   21



(Criteria A), duration (Criteria E), and impairment (Criteria F).  Criteria 
B symptoms are the intrusive re-experiencing of the event through flash-
backs, nightmares, and physiological reactions to reminders.  Criteria C 
symptoms are avoidance and numbing, including detachment from others, 
loss of interest, and avoiding reminders of the event.  Criteria D symptoms 
indicate hyperarousal and include insomnia, irritability, and hypervigilance 
(APA). The DSM-IV-TR requires at least one B symptom, three C symp-
toms, and two D symptoms in order to qualify for a diagnosis of PTSD. 

In an attempt to more closely imitate the requirements of a DSM-IV-TR 
diagnosis, some researchers interpreting data from brief inventories have 
adhered to requirements for the number of symptoms in each symptom 
cluster (Galea et al., 2002; Piotrkowski & Brannen, 2002). Galea et al. used 
items from a modified Diagnostic Interview Schedule for PTSD to deter-
mine “symptoms consistent with current PTSD” by noting the presence of 
symptoms meeting these threshold requirements. Although the symptom 
cluster method still fails to measure duration and impairment criteria re-
quired for definitive diagnosis, this method most closely approximates a 
DSM diagnosis. In addition, research reveals that the numbing and avoid-
ance symptoms of the C category are the markers of PTSD (North et al., 
1999). North et al. found that 94% of subjects who met Criterion C also met 
the criteria necessary for a full PTSD diagnosis. Researchers who cluster 
symptoms may predict those cases likely to qualify as full PTSD by noting 
the participants who report three or more C symptoms, offering a more ac-
curate assessment of PTSD prevalence. A consequence, however, of more 
closely simulating a DSM diagnosis is that the symptom cluster method can 
disregard significant but sub-clinical distress that the other methods detect.

Discussion
There is no common practice for measuring PTSD and stress symp-

toms in research studies. The nature of large empirical studies precludes the 
use of thorough assessments by trained clinicians, the only way to conclu-
sively diagnose PTSD. PTSD cannot be definitively identified through the 
use of brief questionnaires (North & Pfefferbaum, 2002). Hence, studies 
that use cutoff scores or categorize levels of symptom severity are suscep-
tible to gross overestimation of the prevalence of PTSD. Even categoriz-
ing symptoms according to DSM-IV-TR criteria is insufficient, as check-
lists such as the PCL are subjective and often leave out the duration and 
impairment criteria, inaccurately reflecting the individual’s mental health. 

An issue parallel to accurately assessing PTSD is detecting significant 
distress that may not reach a DSM-threshold level. Brett (1996) argues that the 
classification of disorders through the DSM-IV-TR leaves out many clinical-
ly relevant characteristics. Therefore, although categorizing levels of symp-

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Jeon & Marroquin 



tom severity and tallying scores may not be sufficient for determining PTSD 
prevalence, they do reflect the presence of distress, whether sub-clinical or 
qualifying for DSM diagnosis. These studies offer information important for 
gauging mental health and need not be framed strictly in relation to PTSD. 

Conclusion
Careful interpretation and application of published research on studies 

that include Post Traumatic Stress Disorder (PTSD), Acute Stress Disorder 
(ASD), and Post Traumatic Stress Symptoms (PTSS) following traumatic 
events is necessary due to the wide range in study methods currently em-
ployed. We suggest that consumers of such research take careful note of 
three points. First, investigate the use of terminology for PTSD. The authors 
of trauma research articles may use the terms PTSD, ASD, and  PTSS, each 
of which have very different meanings. The correct use and interpretation of 
these terms is critical in making any further interpretations of such studies. 
Second, the use of measures cannot take the place of a clinician’s diagno-
sis. Conclusions drawn through the use of standardized measures must be 
considered merely a part of a complex set of responses to traumatic events. 
Third, the DSM-IV-TR, on which the most commonly used measures and 
clinical diagnoses are based, may fail to recognize persons who are, in fact, 
suffering severely but do not meet the designated criteria. Such classification 
systems may also exclude important information that may be addressed by 
more extensive and holistic means of studying individuals, such as a Person-
In-Environment System assessment that includes their social role, environ-
mental, mental, and physical problems (Williams, Karls, & Wandrei, 1989). 

The role of research studies in informing helping professionals is crucial 
in an environment increasingly focused on evidence-based practice. Media 
publications have an ethical responsibility to accurately report and dissemi-
nate knowledge about trauma study findings to the public. In addition, ad-
vocates for and funders of mental health services must be aware of the po-
tential range of post-trauma outcomes when seeking and offering funding. 
All consumers of research should strive to be informed and must tread care-
fully when extrapolating results from studies of traumatized populations. 

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A Brief Review of Issues in PTSD Research



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Sarah S. Jeon is a second-year Master’s student at the Columbia 
University School of Social Work concentrating in Advanced Generalist 

Practice and Programming within the Family, Youth, and Children’s 
Services field of practice. She is currently an intern at the Lower East Side 
Family Union in New York City. She holds a Bachelor’s degree from Yale 
University in Psychology. Her email address is ssj2011@columbia.edu. 

Terra K. Marroquin is a second-year Master’s student at the Columbia 
University School of Social Work concentrating in Clinical Practice 

within the Contemporary Social Problems field of practice with a minor in 
Research. She is currently an intern at the SURVIVE Community Project 

in New York City. She is hold a Bachelor’s degree from the University 
of California at Berkeley in Psychology and Social Welfare. Her email 

address is tkm2005@columbia.edu.

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Jeon & Marroquin 


