Defence Medical Services Psychological Injuries Unit, Duchess of Kent Psychiatric Hospital
Duchess of Kent Psychiatric Hospital, Catterick Garrison, North Yorkshire, UK
Correspondence: Dr Leigh A. Neal, Bristol Priory Hospital, Heath House Lane, Stapleton, Bristol BS16 1EQ, UK. Tel: 0117 9525255; e-mail: info{at}mhra-uk.com
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ABSTRACT |
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Aims To determine the relationship between post-traumatic stress, depression, alcohol dependence and disability.
Method Seventy armed services personnel were assessed for DSMIV diagnoses of post-traumatic stress disorder, major depressive disorder and alcohol dependence, and with continuous measures of symptoms of post-traumatic stress, depression and alcohol dependence following a traumatic event. These variables, as predictors of disability (using the Sheehan Disability Scale), were analysed using multivariate analysis of variance, analysis of covariance and multiple regression backward elimination models.
Results No significant interaction was found for the diagnostic variables even after controlling for the continuous symptom measures. In the regression models, symptoms of depression were a significant predictor of total disability (R2=0.39). Symptoms of alcohol dependence and post-traumatic stress did not significantly predict disability.
Conclusions Since post-traumatic stress was not found to be associated with disability, its clinical importance may be questionable.
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INTRODUCTION |
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METHOD |
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Structured Clinical Interview for DSMIV
The Structured Clinical Interview for DSMIV (SCID;
First et al, 1997) is
a semi-structured interview used for making DSMIV Axis I diagnoses
(American Psychiatric Association,
1994). It has been shown to be highly reliable, with reported
-values of 0.70-1.00 (First et
al, 2000). The clinician (G.G.) was trained to use the SCID
in accordance with the SCID Users Guide
(First et al, 2000),
and had 12 months experience of using the SCID in a clinical capacity
before the study commenced.
Impact of Event Scale
The Impact of Event Scale (IES;
Horowitz et al, 1979)
is a 15-item self-report scale measuring the current level of subjective
post-traumatic psychological distress (range 0-75). It comprises two
sub-scales recording symptoms of intrusion (range 0-35) and avoidance (range
0-40).
Beck Depression Inventory
The Beck Depression Inventory (BDI; Beck
& Steer, 1993) is a 21-item self-report scale measuring the
severity of depression (range 0-63). A modified version of the BDI was used in
addition to the standard inventory, because item 15 in the latter records the
severity of work disability, which was a dependent variable in this study.
With this item removed, the scale consists of 20 items (range 0-60). For the
purposes of this study, this version was designated the Modified BDI
(M-BDI).
Leeds Dependence Questionnaire
The Leeds Dependence Questionnaire (LDQ;
Raistrick et al,
1994) is a 10-item self-report instrument used to measure the
severity of psychological dependence on alcohol (score range 0-30).
Sheehan Disability Scale
The Sheehan Disability Scale (Sheehan,
1983) is a 3-item self-report scale measuring the severity of
disability in the domains of work, family life/home responsibilities and
social/leisure activities. Each of these three domains is scored on a
ten-point Likert scale, where a score of 0 is not at all
impaired, 5 is moderately impaired and 10 is very
severely impaired. It provides a measure of total functional disability
(range 0-30). It has been shown to have adequate internal reliability
(-coefficients and factor analyses) and construct/criterion related
validity (Leon et al,
1992), and has been used previously as an outcome measure in
studies of PTSD (Neal et al,
1997) and panic disorder
(Klerman, 1988).
Statistical procedures
Multivariate analysis of variance (MANOVA) using the Statistical Package
for the Social Sciences (SPSS, version 9), was used to determine whether there
were between-subject effects and interactions between the factors PTSD,
alcohol dependence disorder and major depressive episode, with Sheehan
Disability Scale scores as dependent variables. Analysis of covariance
(ANCOVA) was conducted with the same factors, but with the continuous
variables as covariates. Significance was determined at the level
P<0.01.
Multiple linear regression models (SPSS, version 9.0) were conducted to
test the associations between the Sheehan Disability Scale scores as dependent
variables and the other continuous measures as independent variables, using a
backward elimination method to allow each independent variable to be included.
While simultaneously adjusting for all variables, nonsignificant variables
were dropped (>0.05). Models were also employed substituting the
M-BDI for the BDI and using all combinations with the intrusion and avoidance
sub-scales of the IES.
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RESULTS |
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MANOVA and ANCOVA |
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Multiple regression analysis
None of the multiple regression models retained the IES score (including
the subscales), LDQ score, time from trauma to assessment or
participants age as significant predictors of functional
disability.
Work disability
Only scores on the BDI (ß=0.11, s.e.=0.03; F=12.5, d.f.=1,68,
P=0.001; R2=0.16) and M-BDI (ß=0.10,
s.e.=0.03; F=11.5, d.f.=1,68, P=0.001;
R2=0.16) remained in the multiple regression models as
significant predictors of work disability.
Impaired family life and home responsibilities
Only scores on the BDI (ß=0.15, s.d.=0.02; F=40.30,
d.f.=1,68, P<0.001; R2=0.38) and M-BDI
(ß=0.15, s.e.=0.03; F=37.15, d.f.=1,68, P<0.001;
R2=0.37) remained in the multiple regression models as
significant predictors of impaired family life and home responsibility.
Impaired social and leisure activities
Only scores on the BDI (ß=0.11, s.e.=0.02; F=21.80,
d.f.=1,68, P<0.001; R2=0.24) and the M-BDI
(ß=0.11, s.e.=0.02; F=19.75, d.f.=1,68, P<0.001;
R2=0.23) remained in the multiple regression models as
significant predictors of impaired social/leisure activity.
Total disability
Only scores on the BDI (ß=0.36, s.e.=0.05; F=47.10,
d.f.=1,68, P<0.001; R2=0.42) and the M-BDI
(ß=0.37, s.e.=0.06; F=42.32, d.f.=1,68, P<0.001;
R2=0.39) remained in the multiple regression models as
significant predictors of total disability.
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DISCUSSION |
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On the other hand, symptoms of depression (scored on the M-BDI) accounted for a significant proportion of the variability in terms of total functional disability (shared variance 39%) and, in particular, in the domain of impairment in family life (shared variance 37%). This is consistent with the finding that depression in the general population determines more work loss than any other single psychiatric disorder (Kessler & Frank, 1997), but runs counter to the contemporary view that PTSD or post-traumatic stress symptoms are the primary cause of disability in people exposed to trauma.
Limitations
The study suffered from several limitations. The results may not be
generalisable because the sample was predominantly male and consisted
exclusively of service personnel. This population has more restrictive
contractual obligations and experiences less social deprivation than is found
in the general population. The measures of disability used were self-reported
and subjective; objective measures of disability (e.g. unemployment or
divorce) might have provided useful additional information. According to
Altman (1991) the sample size
was sufficient (at least 10 times the maximum number of independent variables)
for the multiple regression models to be reliable; however, the measurement
instruments used are subject to considerable error and therefore the sample
size must be considered a possible limitation.
Implications
The finding that depression consequent upon trauma is responsible for a
significant proportion of disability calls into question the relationship
between post-traumatic stress symptoms and depression. Overlap between the
symptoms of post-traumatic stress and of depression (e.g. loss of interest,
irritability, difficulties in remembering and concentration, pessimism about
the future and sleep difficulties) raises the issue of whether PTSD is a
separate diagnostic entity or a variant of post-traumatic depression. This
question has largely been answered by factor analysis
(Silver & Iacono, 1984;
Blanchard et al, 1998)
and neurobiological investigations (Van
Der Kolk, 1994; Yehuda et
al, 1997), which demonstrate that the cluster of PTSD
symptoms does appear to constitute a separate syndromal entity.
If PTSD and depression are separate, the question of their relationship to trauma arises. On the one hand, PTSD, and not depression, may be viewed as the primary psychiatric consequence of traumatic exposure (Kessler et al, 1995). This hypothesis is supported by evidence that the pattern of disruption of the hypothalamic-pituitary axis in patients with comorbid PTSD and depression is significantly different from that in patients with depression alone, unrelated to trauma (Yehuda et al, 1997). If this hypothesis is correct, then our findings may indicate that post-traumatic stress symptoms mediate the development of depression, which then leads to disability. On the other hand, it is possible that PTSD and depression emerge simultaneously after a trauma (Bleich et al, 1997), a hypothesis that is supported by evidence of individuals with a shared genetic predisposition to both PTSD and depression (Davidson et al, 1985). If this hypothesis is correct, our findings may indicate that post-traumatic stress symptoms are epiphenomenal.
Either way, our findings indicate that although post-traumatic stress symptoms may cause distress they may be of questionable clinical significance if they are not a cause of disability. This claim has a number of implications. First, the current emphasis on treating PTSD to minimise disability after psychiatric injury may be misplaced, and treatment of depression may be sufficient to alleviate disability. Second, in personal injury litigation, because of the perceived importance of its role in causing disability, PTSD is separated out for special consideration as a condition for compensation (Judicial Studies Board, 2000). This may not be justified. In conclusion, although the scientific literature has been concerned with whether or not PTSD is a valid diagnostic entity (Summerfield, 2001), this study suggests that if PTSD exists, it may not be as clinically important as has previously been claimed.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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Received for publication March 17, 2003. Revision received September 15, 2003. Accepted for publication October 15, 2003.