ORIGINAL PAPER

Evidence for a psychotic posttraumatic stress disorder subtypebased on the National Comorbidity Survey

Mark Shevlin • Cherie Armour • Jamie Murphy •

James E. Houston • Gary Adamson

Received: 17 November 2009 / Accepted: 20 August 2010 / Published online: 2 September 2010

� Springer-Verlag 2010

Abstract

Purpose This study assessed the distribution of post-

traumatic stress disorder (PTSD) symptoms and psychosis

indicators among a large sample of individuals with a

lifetime diagnosis of PTSD. The identification of a psy-

chotic PTSD subtype was also predicted.

Method Using data from the National Comorbidity Sur-

vey a latent class analysis was conducted on the PTSD

symptoms of intrusion, avoidance, and hyperarousal and

the psychosis hallucination and delusion indicators.

Results Results indicated four latent classes, two of

which had relatively high probabilities of endorsing the

hallucination and delusion indicators. These classes were

associated with a broad range of traumatic experiences.

One particular class had high probabilities of endorsing

both the psychosis indicators and the PTSD symptoms and

was associated with a broad range of comorbid psychiatric

disorders.

Conclusion There was a candidate class that met the

characteristics expected to be evident in a psychotic PTSD

subtype.

Keywords Psychotic PTSD � Community sample �Latent class analysis

Introduction

The Diagnostic and Statistical Manual of Mental Disorders

(DSM-IV) [1] defines the symptoms of posttraumatic stress

disorder (PTSD) in terms of exposure to a traumatic event.

However, there is a growing research literature that has

also identified associations between trauma (especially

early traumatic experience) and diagnoses of psychosis or

the occurrence of psychotic-like experiences [2–6]. The

high rates of psychotic disorder and psychotic symptoms in

PTSD populations [7–9], the phenomenological similarity

of some PTSD and psychotic symptoms [10], and the

shared etiology associated with both forms of psychopa-

thology [11] have led to suggestions of a ‘psychotic PTSD’

subtype.

Sautter et al. [12] identified a group of war veterans who

met the DSM-IV criteria both for psychotic disorder and

for PTSD. This psychotic PTSD group had significantly

higher scores on measures of depression, aggression, and

general psychopathology compared to those with PTSD or

psychosis alone. Ivezic et al. [13] reported that war veter-

ans who experienced PTSD with psychotic symptoms had

high levels of comorbid depression, delusional disorder,

and anxiety disorder. Also, based on a community sample,

Sareen et al. [14] reported an increased likelihood of psy-

chotic symptom experience in individuals who had a life-

time diagnosis of PTSD. In addition this group had

significantly higher probabilities of meeting the criteria for

other psychiatric disorders. These and other studies have

shown that psychotic PTSD groups generally have lower

levels of functioning and higher levels of other psychiatric

problems. While the psychotic PTSD groups in these

studies did not require symptoms to present in any partic-

ular temporal order, Braakman et al. [15] proposed a new

diagnostic entity, PTSD with secondary psychotic features

M. Shevlin (&) � C. Armour � J. Murphy � G. Adamson

School of Psychology, University of Ulster at Magee,

Londonderry BT48 7JL, Northern Ireland, UK

e-mail: m.shevlin@ulster.ac.uk

J. E. Houston

Nottingham Trent University, Nottingham, UK

123

Soc Psychiatry Psychiatr Epidemiol (2011) 46:1069–1078

DOI 10.1007/s00127-010-0281-4

(PTSD-SP), which was characterized by psychotic symp-

toms which were emergent after the onset of PTSD. This

new entity was shown to be associated with a broad range

of comorbid diagnoses.

Many studies alluding to a psychotic PTSD subtype

have been based on the small samples of war veterans [9,

13, 16, 17] making generalizations to other trauma cohorts

difficult. In addition, many studies have used different

assessments in order to classify individuals. Furthermore,

the criteria for psychotic PTSD have been predefined by

the researchers and differ across studies. For example, in

some studies psychotic PTSD was based on the diagnosis

of both PTSD and psychotic disorder [12], whereas other

studies only required some psychotic symptoms to be

present [14].

The primary aim of this study was to test if there was a

homogeneous group of individuals who could be described

in terms of a psychotic PTSD subtype, rather than simply

PTSD with comorbid psychosis. The identification of

homogenous groups, or latent classes, was based on the

latent class analysis (LCA). This analysis allows different

classes (groups) to be objectively identified based on the

patterns of symptom endorsement rather than a priori

definitions imposed by researchers. This study utilized the

same community sample as Sareen et al. [14] who created a

‘‘PTSD with psychotic symptoms’’ group based on a

diagnosis of PTSD and the endorsement of one or more

psychosis indicators. The LCA approach in this study

extended this analysis as it (1) included multiple psychosis

indicators to assess which particular types of psychotic

experience were most commonly endorsed; (2) explicitly

tested for a homogeneous group characterized by a high

probability of psychosis and PTSD symptom endorsement;

(3) allowed for an estimate of the size of such a group; and

(4) estimated the probability of endorsing each psychosis

and PTSD symptom within the group. On the basis of

previous research it was hypothesized that a psychotic

PTSD class would, firstly, be characterized by high prob-

abilities of endorsing both PTSD symptoms and psychosis

indicators. Importantly, psychotic PTSD classes would

have to be qualitatively different, rather than just quanti-

tatively different, from other classes in order to be judged

distinct; classes differing only quantitatively would repre-

sent groups of individuals who differed only in terms of an

underlying continuum of severity.

The second aim of the study was to assess the rela-

tionship between the psychotic PTSD subtype and a range

of traumatic experiences. Variables representing a broad

range of traumatic experiences were used to determine if

there were specific traumas that were associated with

psychotic PTSD. It was also predicted that a psychotic

PTSD subtype would have an increased risk of other

comorbid psychiatric diagnoses compared to non-psychotic

classes. In order for a psychotic PTSD class to be consid-

ered qualitatively, rather than just quantitatively different

from non-psychotic PTSD classes, the odds ratios across

the classes should not indicate a graded response.

Methods

The National Comorbidity Survey (NCS) [18] was a

collaborative epidemiologic investigation (1990–1992)

based on a stratified, multi-stage, area probability sample

of non-institutionalized persons aged between 15 and

54 years. The NCS was conducted across 48 coterminous

states of America and was designed to study the preva-

lence and correlates of DSM-III-R [19] disorders. The

initial survey employed a household sample of over 8,000

respondents and a sub-sample of the original respondents

completed the additional NCS Part II survey (N = 5,877)

that contained a further detailed risk factor battery and

additional diagnoses. Of this sample 48% were male, the

average age was 32 years. A full description of the NCS

is available [18].

Participants

Based on the NCS Part II survey there were 591 partic-

ipants with a lifetime diagnosis of PTSD which repre-

sented a weighted prevalence of 7.3%. The full NCS

population sample had 66 participants with a lifetime

diagnosis of psychosis which represented a weighted

prevalence of 0.7%. There was a positive association

between PTSD and psychosis diagnosis (v2 = 25.89,

df = 1, p = 0.00) with 19 participants receiving a life-

time diagnosis of PTSD and psychosis. This represented

3.2% of the sub-sample of participants who had a lifetime

diagnosis of PTSD.

Subsequent analyses were based on those participants

with a lifetime diagnosis of PTSD after excluding those

with a lifetime diagnosis of psychosis. This sample

(N = 568) had a mean age of 33.55 years (SD = 9.97).

There were more females (69.2%) than males in the PTSD

sample compared to the non-PTSD participants (50.1%)

and this was statistically significant (v2 = 75.05, df = 1,

p = 0.00).

Measurements

Information on symptoms of PTSD, psychosis indicators,

demographic variables, traumatic experiences and other

diagnoses was derived from The Composite International

Diagnostic Interview (CIDI) [20]. The CIDI is a fully

structured interview that produced diagnoses according to

the definitions and criteria of the DSM-III-R [19].

1070 Soc Psychiatry Psychiatr Epidemiol (2011) 46:1069–1078

123

Posttraumatic stress disorder

The Posttraumatic Stress Disorder module of the CIDI

(Section U) was used for the diagnosis of lifetime PTSD

based on the DSM-III-R criteria. Factor analytic research

has suggested that there are eight symptoms, currently

associated with the PTSD diagnosis, that are non-specific

to PTSD, but instead measure dysphoria [21]. Subsequent

studies have reported very high correlations between the

dysphoria factor and measures of depression [22] and low

associations with measures of trauma [23]. Indeed, when

depression scores are controlled for the factor loadings for

the dysphoria factor (and the correlation between the dys-

phoria factor and other PTSD factors) are significantly

attenuated [22]. These findings have led to suggestions for

the removal of the dysphoria symptoms from the list of

PTSD diagnostic criteria [24, 25]. Furthermore, research on

the phenomenological similarity of PTSD and psychotic

symptomologies has focused on the symptoms of intrusion

and hyperarousal [26]. For these reasons, and also to

reduce the number of variables in the analysis, the nine

symptoms that comprised the intrusion (B1–B5), avoidance

(C1, C2), and hyperarousal (D1, D2) symptom clusters

were selected.

The items were as follows:

1. (B1) Did you keep remembering the event when you

did not want to?

2. (B2) Did you keep having dreams or nightmares about

it afterwards?

3. (B3) Did you ever suddenly act or feel as though the

event was happening again, even though it wasn’t?

4. (B4) Did you ever get very upset when you were in a

situation that reminded you of it?

5. (B5) Did you sweat or did your heart beat fast, or did

you tremble when reminded of the upsetting

experience?

6. (C1) Did you try hard not to think about it?

7. (C2) Did you go out of your way to avoid situations

that might remind you of the event?

8. (D4) Did you become overly concerned about danger

or overly careful?

9. (D5) Did you become jumpy or easily startled by

ordinary noises or movements?

Psychosis

The psychosis screening section of the CIDI (Section K)

contained 13 items related to classic psychotic-like symp-

toms involving, for example, persecution, thought inter-

ference, and hallucinations. Items were responded to using

a simple ‘yes’ or ‘no’ response format. The CIDI was used

to assess the lifetime prevalence of non-affective psychosis

(a summary category made up of schizophrenia, schizo-

phreniform disorder, schizoaffective disorder, delusional

disorder, and atypical psychosis). The diagnosis of psy-

chosis was based on the clinical reinterviews administered

by experienced clinicians using an adapted version of

the Structured Clinical Interview for DSM-III-R (SCID)

[27].

For this study eight items were selected that represented

hallucinations and delusions. The items were as follows:

1. (Spy) Believed that people were spying on you or

following you?

2. (Pois) Believed that you were being secretly tested or

experimented on, that someone was plotting against

you, or that someone was trying to poison you or hurt

you?

3. (Mess) Believed that you were being sent special

messages through television or the radio, or that a

program had been arranged just for you alone?

4. (Hyp) Felt strange forces working on you, as if you

were being hypnotized or magic was being per-

formed on you, or you were being hit by laser beams

or X-rays?

5. (Vis) Experience of seeing something or someone that

others present could not see—that is, had a vision

when you were wide awake?

6. (Aud) Experience of hearing things that other people

could not hear, such as noises or a voice?

7. (Olfac) Bothered by strange smells around you that

nobody else was able to smell, perhaps even odors

coming from your own body?

8. (Tact) Unusual feelings inside or on your body, like

being touched when nothing was there or feeling

something moving inside your body?

Demographics

The following background variables, or demographic fac-

tors, were used in this study: age, sex (0 = male,

1 = female), ethnicity (0 = non-white, 1 = white), edu-

cation (0 = less than 16 years education, 1 = ?16 years

education), annual income (0 = $19,000 or more, 1 = less

than $19,000), household composition (0 = does not live

alone, 1 = lives alone).

Traumatic experiences

During the administration of the PTSD module, partici-

pants were provided with a booklet which listed the trau-

matic experiences. Each trauma was numbered and

participants were asked to identify the number of the event

rather than naming it. This has been shown to increase

participant’s willingness to report such information [28].

Soc Psychiatry Psychiatr Epidemiol (2011) 46:1069–1078 1071

123

The traumatic experiences were as follows:

1. You had direct combat experience in a war

2. You were involved in a life-threatening accident

3. You were involved in a fire, flood, or natural disaster

4. You witnessed someone being badly injured or killed

5. You were raped (someone had sexual intercourse

with you when you did not want to by threatening

you or using some degree of force)

6. You were sexually molested (someone touched or

felt your genitals when you did not want them to)

7. You were seriously physically attacked or assaulted

8. You were physically abused as a child

9. You were seriously neglected as a child

10. You were threatened with a weapon, held captive, or

kidnapped

Clinical variables

The CIDI lifetime diagnoses (with hierarchy) of a range of

clinical variables were used: alcohol dependence, drug

dependence, major depression, bipolar disorder, mania, and

generalized anxiety disorder. World Health Organization

field trials of the CIDI have documented good inter-rater

reliability, [29, 30] test–retest reliability [31–33], and

validity of almost all diagnoses [33].

Analysis

Analyses were conducted in three phases. First, a latent class

analysis (LCA) was conducted to determine the correct

number of classes. LCA is a statistical method used to

identify homogeneous groups, or classes, from categorical

multivariate data. In this study, LCA was employed to

determine the number and nature of classes based on the

responses to the nine PTSD items and eight psychosis

screening items. All the variables were declared as cate-

gorical and the model parameters were estimated using

robust maximum likelihood. There was very little missing

data (lowest pairwise covariance coverage was 0.97) and this

was treated using full information maximum likelihood

estimation under the assumption of data missing at random

[34]. The fit of five models (a 2-class model through to a

6-class model) was assessed. Selection of the optimal

number of latent classes was based on the several statistical

fit indices. The statistical fit indices were: Akaike informa-

tion criterion (AIC) [35], Bayesian information criterion

(BIC) [36], sample-size adjusted BIC (ssaBIC) [37], the

bootstrapped likelihood ratio test (BSLRT) [38], and entropy

measures [39]. The information statistics AIC, BIC, and

ssaBIC are goodness-of-fit measures used to compare com-

peting models; lower observed values indicate better fit. The

bootstrap likelihood ratio test was used to compare models

with increasing numbers of latent classes. When a non-sig-

nificant value (p [ 0.05) occurs it suggests that the model

with one less class should be accepted. Entropy is a stan-

dardized measure of how accurately participants are classi-

fied. Entropy values can range from 0 to 1 with higher values

indicating better classification. Recent research has sug-

gested that the BSLRT is the best method for determining the

correct number of classes [40, 41]. In order to use the BSLRT

no weighting variable was used in the part of the analysis.

Second, covariates (demographic variables and traumas)

were added to the model to examine which variables sig-

nificantly predicted class membership. The parameters

linking the covariates with the latent classes were multi-

nomial logistic regression coefficients presented as odds

ratios. Third, the classes were used to predict the clinical

variables. The posterior probabilities from the LCA model

were used to create a variable that assigned each partici-

pant to their most likely class. This variable was then

dummy-coded and used as a predictor variable in a model

with the clinical variables entered as dependent variables.

All analyses were conducted using Mplus 4.21 [41] and the

appropriate weighting variable was used in the second and

third phase of the analyses.

Results

Table 1 shows the frequencies of endorsing the psychosis

screening items for the PTSD and the non-PTSD samples.

The chi-square results show that endorsement of all psy-

chosis items were significantly higher for the PTSD sample

than for the non-PTSD sample. Each psychosis variable

was regressed on the PTSD variable using binary logistic

regression. The resultant odds ratios are reported. This

shows that having a diagnosis of PTSD increased the

likelihood of endorsing any of the psychosis items between

2.45 and 4.22 times.

The fit statistics for the LCA are presented in Table 2. The

4-class solution was considered to be the best fitting model.

The AIC and ssaBIC information statistics were markedly

lower for the 4-class solution compared to the 2- and 3-class

solutions, and the BSLRT indicates that the 5-class solution

is not significantly better than the 4-class solution (and so the

4-class solution should be preferred on the basis of parsi-

mony). The BIC for the 4-class solution is higher than that

for the 3-class solution although the difference is small. The

entropy value (0.66) indicates acceptable classification of

participants. The latent class profile plot is shown in Fig. 1

and the probabilities in Table 3.

Class 1 (N = 94, 16.4%) was characterized by relatively

high probabilities of endorsing two delusional indicators

(Spy and Poison), three hallucination indicators (visual,

olfactory, and tactile) and all PTSD indicators. This class

1072 Soc Psychiatry Psychiatr Epidemiol (2011) 46:1069–1078

123

was labeled ‘High Psychosis-High PTSD’. Class 2 was

smaller than class 1 (N = 59, 10.3%) and had a similar

profile in terms of probability of endorsing the psychosis

indicators. The probabilities were lower than class 1 for all

the PTSD indicators. This class was labeled ‘High Psy-

chosis-Low PTSD’. Class 3 (N = 214, 37.4%) was the

largest class and was characterized by low probabilities of

endorsing the psychosis indicators, but high probabilities

associated with all the PTSD indicators (similar to class 1).

This class was labeled ‘Low Psychosis-High PTSD’. Class 4

(N = 205, 35.8%) was slightly smaller than class 3 and

was characterized by low probabilities of endorsing the

psychosis indicators, and relatively low probabilities

associated with all the PTSD indicators. This class was

labeled ‘Low Psychosis-Low PTSD’. It should be noted

that references to ‘high’ and ‘low’ are relative rather than

absolute.

Table 4 shows the results from the multinomial logistic

regression analysis. The demographic and trauma variables

were entered as predictor variables, with class membership

entered as the dependent variable. Class 4 (Low Psychosis-

Low PTSD) was the reference class. Members of class 1

were more likely to be younger and less likely to live alone.

They were also more likely to have witnessed an injury or

killing. Members of class 2 were less likely to be white and

were also less likely to have been educated for more than

16 years. They were more likely to have experienced a fire,

flood, or natural disaster, were more likely to have been

raped, and to have been neglected as a child. Members of

class 3 were not distinguishable from the reference class on

the basis of demographic variables. They were, however,

more likely to have experienced a range of traumas

including, having been to war, having witnessed an injury

or killing, and having been raped.

Table 1 Endorsement of psychosis screening items by participants with and without PTSD

Non-PTSD count (%)

(N = 5,239)

PTSD count (%)

(N = 572)

v2 (df) p OR (95% CI)

1. Believed that people were spying on you or following you? 565 (10.8) 153 (26.8) 121.70 (1) 0.00 3.03 (2.47–3.71)

2. Believed that you were being secretly tested or experimented

on, that someone was plotting against you, or that someone

was trying to poison you or hurt you?

129 (2.5) 55 (9.6) 86.51 (1) 0.00 4.22 (3.04–5.82)

3. Believed that you were being sent special messages through

the television or the radio or that a program had been

arranged just for you alone?

96 (1.8) 30 (5.3) 28.39 (1) 0.00 2.47 (1.95–4.51)

4. Felt strange forces working on you, as if you were being

hypnotized or magic was being performed on you, or you

were being hit by laser beams or X-rays?

34 (.6) 9 (1.6) 6.02 (1) 0.01 2.45 (1.17–5.14)

5. Experience of seeing something or someone that others

present could not see—that is, had a vision when you were

wide awake?

347 (6.6) 108 (18.9) 107.63 (1) 0.00 3.28 (2.59–4.16)

6. Experience of hearing things that other people could not

hear, such as noises or a voice?

347 (6.6) 93 (16.3) 68.57 (1) 0.00 2.74 (2.14–3.51)

7. Bothered by strange smells around you that nobody else was

able to smell, perhaps even odors coming from your own

body?

172 (3.3) 60 (10.5) 70.50 (1) 0.00 3.45 (2.54–4.70)

8. Unusual feelings inside or on your body, like being touched

when nothing was there or feeling something moving inside

your body?

285 (5.4) 95 (16.6) 105.57 (1) 0.00 3.47 (2.70–4.46)

Table 2 Fit statistics for the latent class analysis of psychosis indicators and PTSD symptoms

Classes Log likelihood AIC BIC ssaBIC Entropy BSLRT p

2 -3936.70 7943.41 8095.63 7984.52 0.69 347.68 0.00

3 -3856.08 7818.17 8048.68 7880.42 0.66 161.24 0.00

4 -3821.30 7784.61 8093.40 7868.01 0.66 69.55 0.00

5 -3801.66 7781.32 8168.40 7885.86 0.68 39.29 0.36

6 -3780.92 7775.84 8241.19 7901.52 0.71 35.18 0.37

AIC Akaike information criterion, BIC Bayesian information criterion, ssaBIC sample-size adjusted BIC, BSLRT Bootstrapped likelihood ratio

test

Soc Psychiatry Psychiatr Epidemiol (2011) 46:1069–1078 1073

123

Table 5 shows the results of the logistic regression

model. This model used dummy-coded variables to repre-

sent three latent classes. Class 4 (Low Psychosis-Low

PTSD) was the reference class therefore the odds ratios

associated with the other classes indicated the increased

likelihood of a CIDI diagnosis compared to class 4. For

class 1 there was a significant increase in the likelihood of a

diagnosis of alcohol dependence, major depression, bipolar

disorder, mania, and generalized anxiety disorder. For class

2 there was a significant increase in the likelihood of a

diagnosis of mania and generalized anxiety disorder. For

class 3 there was a significant increase in the likelihood of a

diagnosis of bipolar disorder and generalized anxiety

disorder.

Discussion

This study aimed to test if there was a homogeneous group

of individuals who could be described in terms of a psy-

chotic PTSD subtype. It was further predicted that such a

group would have increased risks of other comorbid

psychiatric diagnoses. It was found that participants with a

lifetime diagnosis of PTSD were significantly more likely

to endorse seven of the eight CIDI psychosis indicators

compared to the non-PTSD group. The rates of endorse-

ment for this group for visual (19%), auditory (19%), and

tactile (19%) hallucinations were all high compared to

other general population estimates [42, 43]. However, these

were similar to the rates for NCS participants who had been

victims of childhood neglect or abuse, or molestation under

the age of 16 [4]. These findings are consistent with pre-

vious research that reported an association between trauma

and the experience of psychosis-like experiences [44] or a

diagnosis of psychosis [45].

The LCA indicated that there were four homogenous

groups. Classes 1 and 4 differed quantitatively across all

the variables, and the differences among the other classes

were qualitative: the probabilities of endorsement did not

increase or decrease uniformly across classes. Two of these

groups had relatively high probabilities associated with the

psychosis indicators. For class 1 the probabilities of

endorsing the first paranoia (Spy) indicator and three of the

hallucination (Vis, Aud, and Tact) indicators were high,

Fig. 1 Latent class profile plot displaying response probabilities

across psychosis indicators and PTSD symptoms. Psychosis 1Believed that people were spying on you or following you? Psychosis2 Believed that you were being secretly tested or experimented on,

that someone was plotting against you, or that someone was trying to

poison you or hurt you? Psychosis 3 Believed that you were being

sent special messages through television or the radio, or that a

program had been arranged just for you alone? Psychosis 4 Felt

strange forces working on you, as if you were being hypnotized or

magic was being performed on you, or you were being hit by laser

beams or X-rays? Psychosis 5 Experience of seeing something or

someone that others present could not see—that is, had a vision when

you were wide awake? Psychosis 6 Experience of hearing things that

other people could not hear, such as noises or a voice? Psychosis 7Bothered by strange smells around you that nobody else was able to

smell, perhaps even odors coming from your own body? Psychosis 8Unusual feelings inside or on your body, like being touched when

nothing was there or feeling something moving inside your body? B1Did you keep remembering the event when you did not want to?

B2 Did you keep having dreams or nightmares about it afterwards? B3Did you ever suddenly act or feel as though the event was happening

again, even though it wasn’t? B4 Did you ever get very upset when

you were in a situation that reminded you of it? B5 Did you sweat or

did your heart beat fast, or did you tremble when reminded of the

upsetting experience? C1 Did you try hard not to think about it? C2Did you go out of your way to avoid situations that might remind you

of the event? D4 Did you become overly concerned about danger or

overly careful? D5 Did you become jumpy or easily startled by

ordinary noises or movements

1074 Soc Psychiatry Psychiatr Epidemiol (2011) 46:1069–1078

123

indeed higher than the probabilities of endorsing some

PTSD symptoms (B2, B3, B5, and D5) for classes 2 and 4.

This may be due to the intrusive nature of these psychotic

indicators. Class 2 had a similar pattern of probabilities to

class 1 for each of the psychosis indicators, although the

probabilities of endorsing the PTSD symptoms were lower.

The high probabilities of endorsement may be attributable

to the phenomenological similarity of intrusive thoughts

and flashbacks that are indicative of PTSD and hallucina-

tions/delusions [45, 46]. Many studies [14, 45] have found

that individuals with PTSD who reported psychotic

symptoms had higher levels of psychopathology than those

with a diagnosis of either PTSD or psychosis alone. The

findings in this study are consistent with previous research,

but only for class 1. Individuals in class 1 were signifi-

cantly more likely to have a diagnosis of alcohol depen-

dence, depression, bipolar disorder, mania, and GAD

compared to the Low PTSD-Low Psychosis class (class 4)

while the odds ratios for class 2 were significant for mania

and GAD only. On the basis of the profile of endorsement

of PTSD symptoms and psychosis indicators, classes 1 and

2 could be argued to represent a psychotic PTSD subtype;

however, only class 1 displayed elevated levels of overall

psychopathology.

The associations between trauma exposure and class

membership did not clearly delineate the classes. Table 4

shows that class 1 membership was significantly predicted

only by having witnessed someone being badly injured or

killed. However, there were three significant trauma pre-

dictors for classes 2 and 3.

Overall, class 1 had two of the main features that would

be expected in a psychotic PTSD subtype. The class was

characterized by a high probability of endorsing the psy-

chosis indicators and had higher levels of psychopathology.

However, there was no clear etiological pathway based on

trauma exposure that differentiated this class from the other

classes. However, class 1 was consistent with previous

descriptions of the psychotic PTSD subtype. First, Kastelan

et al. [17] reported that the severity of hyperarousal

symptoms reported by PTSD diagnosed war veterans was

positively associated with psychotic symptoms. In this

study, class 1 had high levels of hyperarousal (D4 and D5)

compared to the other high psychosis class. Second,

Braakman et al. [15] noted that Hispanic and African

Americans displayed a higher incidence of PTSD-SP. In

this study the ethnicity variable had a significant effect on

class 2 only, indicating an increased likelihood of being

non-white. Furthermore, class 1 compared to class 2 had

high probabilities of endorsing the two avoidance symp-

toms (C1, C2). Trauma-related avoidance potentially

compromises social relations and promotes social isolation.

It has also been suggested that this isolation in turn

potentially reduces the possibility for reality testing, thusTa

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?

Soc Psychiatry Psychiatr Epidemiol (2011) 46:1069–1078 1075

123

enhancing vulnerability for psychotic experiences [47, 48].

Additionally, it has been proposed that both the intrusive

memories and flashbacks that are characteristic of the

re-experiencing and the hyperarousal symptom clusters of

PTSD, may also constitute chronic stressors which may

worsen symptom experience and enhance psychosis vul-

nerability [45].

This study has provided a symptom-based description of

a homogenous group that could be described in terms of a

psychotic PTSD subtype. In addition, it has shown that this

group has a clinical profile that is significantly poorer to all

other participants. However, the study had some limitations

and fails to provide sufficient evidence for a valid diag-

nostic entity. No information on the etiology, course,

treatment response, or biological basis for psychotic PTSD

was available. In addition there were limitations in terms of

the methodology. First, all measurements used in this study

are self-reports based on a structured interview rather than

clinical assessments. Second, the measurement of psycho-

sis-like symptoms can be confounded by numerous factors,

such as respondents misunderstandings, the nature of the

question, or normalizing the experience. In addition, it is

not easy from lay-interviews to distinguish reports of odd

experiences from true psychotic experiences. Third, whilst

self-report measures of psychotic experience may be

accurate in clinical samples, they may be falsely denied in

the general population due to the perceived stigma asso-

ciated with such experiences [2, 48, 49]. Finally, the

inclusion of those with a lifetime diagnosis of psychosis

may have provided a useful comparison group for the

Table 4 Regression coefficients (odds ratios) for demographic and trauma variables predicting latent classes

Predictor Class 1

High Psychosis–High PTSD

Class 2

High Psychosis–Low PTSD

Class 3

Low Psychosis–High PTSD

Age 0.96* (0.92–0.99) 1.01 (0.98–1.03) 0.99 (0.97–1.01)

Sex (female) 0.94 (0.38–2.27) 0.91 (0.40–2.08) 1.54 (0.84–2.81)

Ethnicity (white) 0.54 (0.26–1.10) 0.47* (0.23–0.97) 1.02 (0.57–1.84)

Education ([16 years) 0.48 (0.18–1.27) 0.28* (0.12–0.66) 0.70 (0.37–1.34)

Income (\$19,000) 1.63 (0.85–3.14) 1.67 (0.88–3.15) 1.19 (0.72–1.99)

Household composition (lives alone) 0.30* (0.18–0.69) 1.07 (0.49–2.32) 0.72 (0.40–1.29)

War 1.08 (0.30–3.92) 1.03 (0.24–4.37) 2.96* (1.05–8.29)

Accident 1.51 (0.79–2.86) 1.14 (0.57–2.28) 1.36 (0.80–2.31)

Fire/flood/natural disaster 2.77 (1.39–5.49) 4.30* (2.12–8.73) 1.22 (0.69–2.16)

Witnessed someone being badly injured or killed 2.58* (1.35–5.02) 0.92 (0.42–1.99) 1.74* (1.03–2.92)

Raped 1.77 (0.84–3.73) 2.35* (1.12–4.93) 1.78* (1.02–3.09)

Molested 1.49 (0.77–2.90) 0.94 (0.48–1.84) 1.03 (0.68–1.71)

Attacked/physically assaulted 1.09 (0.54–2.24) 0.96 (0.48–2.09) 1.16 (0.65–2.08)

Abused as a child 1.87 (0.89–3.91) 0.51 (0.23–1.13) 1.20 (0.69–2.07)

Neglected as a child 0.78 (0.32–1.93) 2.68* (1.30–5.56) 0.74 (0.38–1.44)

Threatened with a weapon/held captive/kidnapped 1.50 (0.75–2.99) 0.39* (0.16–0.92) 1.08 (0.60–1.94)

95% confidence intervals in parenthesis

* Indicates statistical significance

Table 5 Regression coefficients (odds ratios) for latent classes predicting lifetime CIDI diagnoses

Alcohol

dependence

Drug

dependence

Major

depression

Bipolar

disorder

Mania Generalized anxiety

disorder

Class 1 2.11* 1.38 3.04* 8.07* 12.07* 3.44*

High Psychosis–High PTSD (1.10–4.05) (0.66–2.88) (1.60–5.76) (2.54–25.60) (1.14–127.41) (1.49–7.96)

Class 2 1.84 2.03 1.34 3.69 22.11* 2.96*

High Psychosis–Low PTSD (0.86–3.96) (0.85–4.85) (0.62–2.86) (0.63–21.58) (1.84–264.55) (1.20–7.26)

Class 3 1.30 1.12 1.60 3.12* 1.05 2.89*

Low Psychosis–High PTSD (0.74–2.27) (0.58–2.17) (0.94–2.73) (1.04–9.30) (0.06–17.00) (1.43–5.83)

Class 4 is the reference class

* Indicates statistical significance (p \ 0.05)

1076 Soc Psychiatry Psychiatr Epidemiol (2011) 46:1069–1078

123

psychotic PTSD subtype class in terms of comorbid psy-

chiatric diagnoses.

The current findings may have important implications

regarding the conceptualization of trauma-related diagno-

ses. It is notable that the clinical profile of the High PTSD-

High Psychosis class was significantly poorer than the

remainder of this PTSD sample. If these findings are indeed

representative of trauma psychopathology then traumatized

individuals diagnosed with PTSD might also experience

psychosis related symptoms, and if these individuals in turn

exhibit an elevated probability of clinical comorbidity, then

it would seem important that clinicians screen for the

presence of symptoms that currently lie beyond the diag-

nostic boundaries of a PTSD diagnosis.

References

1. American Psychiatric Association (1994) Diagnostic and statis-

tical manual of mental disorders, 4th edn. American Psychiatric

Association, Washington

2. Bebbington PE, Kuipers L (1992) Social causation of schizo-

phrenia. In: Bhugra D, Leff JP (eds) Principles of social psy-

chiatry. Blackwell, Oxford

3. Janssen I, Krabbendam L, Bak M, Hanssen M, Vollebergh W, de

Graaf R et al (2004) Childhood abuse as a risk factor for psy-

chotic experiences. Acta Psychiatr Scand 109:38–45

4. Shevlin M, Dorahy M, Adamson G (2007) Childhood traumas

and hallucinations: an analysis of the National Comorbidity

Survey. J Psychiatr Res 41:222–228

5. Shevlin M, Dorahy MJ, Adamson G (2007) Trauma and psy-

chosis: an analysis of the National Comorbidity Survey. Am J

Psychiatry 164:166–169

6. Elklit A, Shevlin M (2010) Female sexual victimization predicts

psychosis: a case-control study based on the Danish registry

system. Schizophr Bull. doi:10.1093/schbul/sbq048

7. Hamner MB, Frueh BC, Ulmer HG, Arana GW (1999) Psychotic

features and illness severity in combat veterans with chronic

posttraumatic stress disorder. Biol Psychiatry 45:846–852

8. Hamner MB, Fossey MD (1993) Psychotic symptoms associated

with posttraumatic-stress-disorder. Neuropsychopharmacology

9:S121–S122

9. Hamner MB (1997) Psychotic features and combat-associated

PTSD. Depress Anxiety 5:34–38

10. Morrison APSC, Read J, Turkington D (2005) Trauma and psy-

chosis: theoretical and clinical implications. Acta Psychiatr Scand

112:327–329

11. Seedat S, Stein MB, Oosthuizen PP, Emsley RA, Stein DJ (2003)

Linking posttraumatic stress disorder and psychosis—a look at

epidemiology, phenomenology, and treatment. J Nerv Ment Dis

191:675–681

12. Sautter FJ, Brailey K, Uddo MM, Hamilton MF, Beard MG,

Borges AH (1999) PTSD and comorbid psychotic disorder:

comparison with veterans diagnosed with PTSD or psychotic

disorder. J Trauma Stress 12:73–88

13. Ivezic S, Bagaric A, Oruc L, Mimica N, Ljubin T (2000) Psy-

chotic symptoms and comorbid psychiatric disorders in a Cro-

ation combat related posttraumatic stress disorder sample. Croat

Med J 41:179–183

14. Sareen J, Cox BJ, Goodwin RD, Asmundson GJG (2005)

Co-occurrence of posttraumatic stress disorder with positive

psychotic symptoms in a nationally representative sample.

J Trauma Stress 18:313–322

15. Braakman MH, Kortman FAM, van den Brink W (2009) Validity

of ‘posttraumatic stress disorder with secondary psychotic fea-

tures’: a review of the evidence. Acta Psychiatr Scand 199:15–24

16. David D, Kutcher GS, Jackson EI, Mellman TA (1999) Psychotic

symptoms in combat-related posttraumatic stress disorder. J Clin

Psychiatry 60:29–32

17. Kastelan A, Franciskovic T, Moro L, Roncevic-Grzeta I, Grkovic

J, Jurcan V et al (2007) Psychotic symptoms in combat-related

post-traumatic stress disorder. Mil Med 172:273–277

18. Kessler RC (1994) The National Comorbidity Survey of the

United States. Int Rev Psychiatry 6:365–376

19. American Psychiatric Association (1987) Diagnostic and statis-

tical manual of mental disorders, 3rd edn, revised (DSM-III-R).

American Psychiatric Association, Washington

20. World Health Organization (1990) Composite International

Diagnostic Interview (CIDI), version 1.0. World Health

Organization

21. Simms LJ, Watson D, Doebbeling BN (2002) Confirmatory

factor analyses of posttraumatic stress symptoms in deployed and

nondeployed veterans of the Gulf War. J Abnorm Psychol

111:637–647

22. Elklit A, Armour C, Shevlin M (2010) Testing alternative factor

models of PTSD and the robustness of the dysphoria factor.

J Anxiety Disord 24:147–154

23. Armour C, Shevlin M (2010) Testing the dimensionality of PTSD

and the specificity of the dysphoria factor. J Loss Trauma 15:11–27

24. Ford JD, Elhai JD, Ruggiero KJ, Frueh BC (2009) Refining

posttraumatic stress disorder diagnosis: evaluation of symptom

criteria with the National Survey of Adolescents. J Clin Psychi-

atry 70:748–755

25. Spitzer RL, First MB, Wakefield JC (2007) Saving PTSD from

itself in DSM-V. J Anxiety Disord 21:233–241

26. Morrison AP, Frame L, Larkin W (2003) Relationships between

trauma and psychosis: a review and integration. Br J Clin Psychol

42:331–353

27. Spitzer RL, Williams JBW, Gibbon M, First MB (1992) The

Structured Clinical Interview for DSM-III-R (SCID) I: history,

rationale, and description. Arch Gen Psychiatry 49:624–629

28. Kessler RC, Borges G, Walters EE (1999) Prevalence of and risk

factors for lifetime suicide attempts in the national comorbidity

survey. Arch Gen Psychiatry 56:17–626

29. Wittchen HU, Robins LN, Cottler LB, Sartorius N, Burke JD,

Regier D (1991) Cross-cultural feasibility, reliability and sources

of variance of the Composite International Diagnostic Interview

(CIDI). Br J Psychiatry 159:645–653

30. Cottler LB, Robins LN, Grant BF, Blaine J, Towle LH, Wittchen

HU et al (1991) The CIDI-core substance-abuse and dependence

questions—cross-cultural and nosological issues. Br J Psychiatry

159:653–658

31. Wacker HR, Battegay R, Muellejans R, Schloesser C (1990)

Using the CIDI-C in the general-population. Psychiatry: A World

Perspective 900:138–143

32. Janca A, Robins LN, Bucholz KK, Early TS, Shayka JJ (1992)

Comparison of Composite International Diagnostic Interview and

Clinical DSM-III-R Criteria Checklist Diagnoses. Acta Psychiatr

Scand 85:440–443

33. Schafer JL, Graham JW (2002) Missing data: our view of the

state of the art. Psychol Methods 7:147–177

34. Akaike H (1987) Factor analysis and AIC. Psychometrika

52:317–332

35. Scwartz G (1978) Estimating the dimension of a model. Ann Stat

6:461–464

36. Sclove SL (1987) Application of model selection criteria to some

problems in multivariate analysis. Psychometrika 52:333–343

Soc Psychiatry Psychiatr Epidemiol (2011) 46:1069–1078 1077

123

37. McLachlan GJ, Peel D (2000) Finite mixture models. New York,

Wiley-Interscience

38. Ramaswamy V, DeSarbo W, Reibstein D, Robinson W (1993) An

empirical pooling approach for estimating marketing mix elas-

ticities with PIMS data. Marketing Sci 12:103–124

39. Nylund KL, Asparoutiov T, Muthen BO (2007) Deciding on the

number of classes in latent class analysis and growth mixture

modeling: a Monte Carlo simulation study. Struct Equ Model

14:535–569

40. Muthen BO, Muthen L (1998–2007) Mplus Users Guide, 5th edn.

Muthen & Muthen, Los Angeles

41. Scott J, Welham J, Martin G, Bor W, Najman J, O’Callaghan M

et al (2008) Demographic correlates of psychotic-like experiences

in young Australian adults. Acta Psychiatr Scand 118:230–237

42. Johns LC, Hemsley D, Kuipers E (2002) A comparison of

auditory hallucinations in a psychiatric and non-psychiatric

group. Br J Clin Psychol 41:81–86

43. Bebbington PE, Bhugra D, Brugha T, Singleton N, Farrell M,

Jenkins R et al (2004) Psychosis, victimisation and childhood

disadvantage—evidence from the second British National Survey

of Psychiatric Morbidity. Br J Psychiatry 185:220–226

44. Mueser KT, Essock SM, Haines M, Wolfe R, Xie HY (2004)

Posttraumatic stress disorder, supported employment, and out-

comes in people with severe mental illness. CNS Spectr

9:913–925

45. Shaw K, McFarlane AC, Bookless C, Air T (2002) The aetiology

of postpsychotic posttraumatic stress disorder following a psy-

chotic episode. J Trauma Stress 15:39–47

46. Bendall S, McGorry P, Krstev H (2006) The trauma of being

psychotic: an analysis of posttraumatic stress disorder in response

to acute psychosis. In: Larkin W, Morrison AP (eds) Trauma and

psychosis: new directions for theory and therapy. Routledge,

London, pp 58–74

47. Cresswell CM, Kuipers L, Power MJ (1992) Social networks and

support in long-term psychiatric-patients. Psychol Med 22:

1019–1026

48. Bebbington PE, Kuipers L (1994) The social management of long

standing schizophrenia: the deployment of service resources.

Clinician 12:17–29

49. Butzlaff RL, Hooley JM (1998) Expressed emotion and psychi-

atric relapse—a meta-analysis. Arch Gen Psychiatry 55:547–552

1078 Soc Psychiatry Psychiatr Epidemiol (2011) 46:1069–1078

123