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166 Am J Psychiatry 164:1, January 2007
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Brief Report
Trauma and Psychosis: An Analysis of the National Comorbidity Survey
Mark Shevlin, Ph.D.
Martin J. Dorahy, D.Clin.Psych., Ph.D.
Gary Adamson, Ph.D.
Objective: The authors hypothesized that the likelihood of
psychosis classification would increase with traumatic experi-
ences.
Method: Data from the National Comorbidity Survey were
used to estimate the relationship between interpersonal
trauma and the likelihood of a classification of psychosis.
Results: Childhood physical abuse predicted psychosis, and
there was a significant cumulative relationship between trauma
and psychosis, with number of trauma types experienced in-
creasing the probability of psychosis.
Conclusions: Overall, physical abuse predicted psychosis. In
addition, a significant gender-by-rape interaction was observed,
with rape having higher predictive value for psychosis in male
subjects.
(Am J Psychiatry 2007; 164:166–169)
Renewed interest in the etiology of psychotic disor-
ders and symptoms (1) has sharpened the focus on psy-
chosocial factors. Read et al. (2) reviewed the relation-
ship between child maltreatment and psychosis and
argued for a potential causal connection. In a large-scale
prospective study, Janssen et al. (3) reported that child
abuse before the age of 16 was a significant risk factor for
psychotic symptoms. In a recent analysis of the second
British National Survey of Psychiatric Morbidity (4),
traumatic experiences were associated with the pres-
ence of a psychotic illness rather than other types of psy-
chiatric difficulty. After depression and the shared con-
tribution of other traumas were controlled, lifetime
factors such as sexual abuse, running away from home,
and experiencing serious injury, illness, or assault were
demonstrated to increase the likelihood of psychosis
classification. However, traumatic experiences in this
study were, in part, relatively nonspecific, assessing sev-
eral types in the one item (e.g., “victim of serious injury,
illness, or assault”), and were broadly defined as those
related to both interpersonal stress (e.g., sexual abuse,
bullying) and noninterpersonal stress (e.g., being home-
less). An examination of data from the National Comor-
bidity Survey allowed us to clarify and expand on previ-
ous findings. Specifically, we focused on whether
interpersonal threats to physical and sexual integrity
were related to psychosis in a large national sample. We
hypothesized that traumatic experiences would increase
Am J Psychiatry 164:1, January 2007 167
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the likelihood of a classification of psychosis. In addi-
tion, we examined the interaction effects of gender and
trauma on psychosis.
Method
The National Comorbidity Survey was a collaborative epi-
demiologic investigation (1990–1992) based on a stratified,
multistage area probability sample of noninstitutionalized
persons between 15 and 54 years of age in the coterminous
United States designed to study the prevalence and correlates
of DSM-III-R disorders. The initial survey employed a house-
hold sample of over 8,000 respondents, and a subsample of
the original respondents completed the additional Part 2 sur-
vey, which contained a detailed risk factor battery and addi-
tional diagnoses. All analyses reported in this article were con-
ducted from the National Comorbidity Survey Part 2 data (N=
5,877).
A modified version of the Composite International Diag-
nostic Interview was used to assess the lifetime prevalence of
nonaffective psychosis (a summary category consisting of
schizophrenia, schizophreniform disorder, schizoaffective
disorder, delusional disorder, and atypical psychosis). The Na-
tional Comorbidity Survey also elicited information on the oc-
currences of traumatic events (these were presented to the re-
spondent on a list and referenced only by number). We
selected five questions that represented childhood victimiza-
tion, threats to physical integrity, and threats to sexual integ-
rity. Specifically, a “yes” or “no” response was required to the
following statements:
1. You were seriously neglected as a child.
2. You were physically abused as a child.
3. You were seriously physically attacked or assaulted.
4. You were raped (someone had sexual intercourse with you
when you did not want to by threatening you or using some
degree of force).
5. You were sexually molested (someone touched or felt your
genitals when you did not want them to).
6. No explicit age limit was stated for “childhood” events.
Results
The traumatic experiences and psychosis classifica-
tions of the National Comorbidity Survey respondents
are presented in Table 1. All analyses were conducted
using hierarchical binary logistic regression in SPSS
11.0 where the model was built sequentially, retaining
only those variables that were significant in each block.
The following background variables were used as pre-
dictors in the first block: gender, age, depression (life-
time prevalence), family history (two variables were
used to represent lifetime prevalence of depression in
respondent’s mother and father), urbanicity (a binary
variable representing urban or nonurban location),
and income (four-category variable). The only signifi-
cant predictor was depression (odds ratio=9.74, 95%
CI=5.14–18.47; z=48.75, p<0.001). The trauma variables
were entered in the second block, and physical abuse
was the only significant predictor (odds ratio=2.68, 95%
CI=1.11–6.52; z=4.76, p=0.03), although all the odds ra-
tios were similar in magnitude and direction ranging
from 1.50 to 2.68. The difference in model fit between a
logistic model with all the odds ratios constrained to be
equal and another in which each variable had a unique
effect was not statistically significant (∆χ
2
=0.714, ∆df=
4, p=0.94), indicating significant homogeneity among
the effects of the trauma variables. The estimated com-
mon odds ratio for all variables was statistically signifi-
cant (odds ratio=1.80, 95% CI=1.51–2.14; z=42.90,
p<0.001). In the third block, five gender-by-trauma in-
teractions were included, and the gender-by-rape in-
teraction was found to be significant. The final model
indicated that psychosis could be predicted by depres-
sion (odds ratio=5.09, 95% CI=2.99–8.66; z=36.06,
p<0.001), physical abuse (odds ratio=3.45, 95% CI=
TABLE 1. Traumatic Experiences Among National Comorbidity Survey Respondents by Psychosis Classification
a
Trauma N
Psychosis Absent Psychosis Present
N% N %
Rape
No 5,616 5,583 99.4 33 0.6
Yes 258 249 96.5 9 3.5
Total 5,874 5,831 99.3 42 0.7
Serious attack or assault
No 5,382 5,351 99.4 31 0.6
Yes 492 480 97.6 12 2.4
Total 5,873 5,831 99.3 42 0.7
Physically abused as child
No 5,544 5,513 99.5 30 0.5
Yes 246 234 95.2 12 4.8
Total 5,790 5,747 99.3 42 0.7
Neglected as child
No 5,621 5,587 99.4 34 0.6
Yes 164 156 94.9 8 5.1
Total 5,786 5,743 99.3 42 0.7
Sexually molested
No 5,454 5,425 99.5 29 0.5
Yes 416 403 96.9 13 3.1
Total 5,870 5,828 99.3 42 0.7
a
A weight variable was used to adjust data to approximate the national population distributions of the cross-classifications of age, sex, race/
ethnicity, marital status, education, living arrangements, region, and urbanicity as defined by the 1989 U.S. National Health Interview Survey.
168 Am J Psychiatry 164:1, January 2007
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1.90–6.25; z=3.45, p<0.001), and the gender-by-rape in-
teraction (odds ratio=1.58, 95% CI=1.15–2.18; z=1.58,
p<0.001). With depression removed from the model,
the effects for physical abuse (odds ratio=4.49, 95% CI=
2.47–8.12; z=24.56, p<0.001) and the gender-by-rape in-
teraction (odds ratio=1.88, 95% CI=1.37–2.59; z=15.15,
p<0.001) were slightly higher. To interpret the interac-
tion, the same analysis was rerun separately for male
and female subjects (after replacing the interaction
term with only the rape variable). The effect for the
rape variable was statistically higher for male subjects
(odds ratio=5.81, 95% CI=1.24–27.17; z=4.99, p=0.02)
than female subjects (odds ratio=4.05, 95% CI=2.02–
8.08; z=5.67, p<0.001). With depression removed the ef-
fects for male subjects (odds ratio=8.19, 95% CI=1.85–
36.32; z=7.66, p=0.01) and female subjects (odds ratio=
5.65, 95% CI=2.87–11.10; z=25.30, p<0.001) were
slightly higher.
To examine the cumulative effect of traumas, psychosis
was regressed on an aggregate variable created to repre-
sent the number of traumatic events experienced by each
respondent (0, 1, 2, and ≥3). The aggregate trauma vari-
able was entered as a categorical predictor in the second
block of a logistic regression, with depression entered in
the first block. The first level (no traumatic experiences)
was used as a reference category for a simple contrast.
The odds ratios for one traumatic experience (odds ratio=
2.12, 95% CI=1.13–3.99; z=5.46, p=0.02), two experiences
(odds ratio=3.89, 95% CI=1.83–8.28; z=12.41, p<0.001),
and three or more experiences (odds ratio=7.96, 95% CI=
3.91–16.17; z=32.86, p<0.001) indicated an increasing
likelihood of psychosis as the number of trauma types ex-
perienced increased.
Discussion
Childhood physical abuse was the only significant
predictor of psychosis in the total sample after depres-
sion was controlled. Read et al. (2) argued that rather
than the diathesis for psychotic illnesses being solely re-
lated to a biological-genetic vulnerability factor, it may
for some be related to early neurodevelopmental alter-
ations resulting from childhood abuse. The current find-
ings support the notion that childhood physical abuse
may be one experience that alters neurobiological devel-
opment and increases the risk for a psychotic illness.
Moreover, cumulative trauma may also operate to fur-
ther heighten risk, given the positive association be-
tween the number of traumatic experience types and
risk of a psychotic illness.
Although childhood physical abuse was the only sig-
nificant predictor of psychosis, there was significant ho-
mogeneity among the effects for all trauma variables,
and the common odds ratio for all traumas was statisti-
cally significant (odds ratio=1.80, 95% CI=1.51–2.14; z=
42.90, p<0.001) although lower than that for childhood
physical abuse. This suggests the effects of the other
traumas should not be ruled out as possible predictive
factors for psychosis, since their odds ratios were not sig-
nificantly different than that for childhood physical
abuse.
In keeping with the significant gender differences re-
ported in the onset, phenomenology, and course of psy-
chotic symptoms (5, 6), it is perhaps not surprising that
victimization experiences were related to psychosis dif-
ferentially for male and female subjects, with the odds ra-
tios associated with rape being significantly higher for
male subjects. The subversion of both biological roles
(i.e., males’ evolutionary and anatomical function as
“penetrators” during coitus) and cultural roles (e.g., the
Western enculturation of males toward power) in male
rape may come to bear on its profound association with
psychosis in men. As depression was controlled in the
analysis, the higher rate of affective symptoms often re-
ported in female subjects with psychotic illnesses (7)
cannot account for either gender differences in the sig-
nificance of specific victimization experiences or the link
between physical childhood abuse and psychosis in fe-
male subjects.
Although retrospective reporting of childhood trauma,
especially from individuals with psychotic illnesses, rep-
resents one potential methodological problem, previous
work has indicated that such reports are typically reliable
(8). The findings highlight the importance of evaluating
interpersonal victimization experiences during clinical
assessment to ensure comprehensive formulation of the
patient’s difficulties and appropriate treatment planning
(2, 4).
Received June 3, 2005; revisions received Aug. 3 and Nov. 7, 2005;
accepted Dec. 28, 2005. From the Psychiatric Epidemiology Research
Unit, University of Ulster at Magee College; the Trauma Resource
Centre, North & West Belfast HSS Trust; and the School of Psychology,
The Queen’s University of Belfast. Address correspondence and re-
print requests to Dr. Shevlin, Psychiatric Epidemiology Research Unit,
University of Ulster at Magee College, Londonderry BT48 7Jl, United
Kingdom; m.shevlin@ulster.ac.uk (e-mail).
All authors report no competing interests.
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