Regional Health Authority Twente, Enschede Firework Disaster Health Monitoring Project, Postbus 1400, 7500 BK Enschede, The Netherlands
Specialty Programme for Psychotrauma, Academic Medical Centre of the University of Amsterdam, The Netherlands
Netherlands Institute for Health Services Research (NIVEL), Utrecht, The Netherlands
Neal et al (2004) recently found no association between post-traumatic stress and judgement of disability. Therefore, they concluded that the clinical importance of post-traumatic stress disorder (PTSD) and its symptoms may be questionable. However, in our opinion their conclusions need additional consideration.
First, their multivariate analysis of variance compared the degree of disability of persons with PTSD with that of people with other mental health problems. From their results they could only conclude that PTSD caused no additional disability compared with other mental health problems. Moreover, from a statistical point of view, the sample size is not sufficiently large, especially when one tries to find differences between groups given the significance level used (P=0.01). In addition, the authors do not give insight in the multicollinearity between the independent variables of the multiple regression analysis; the expected high intercorrelations may have influenced the results.
Second, is it not strange to question disability in people with PTSD, major depressive disorder or alcohol dependence, while disability in social or professional functioning or in other important areas is a requirement for all DSM-IV diagnoses? Also, the authors took subjective judgement of disability as their main outcome measure and not objective measures of disability, such as the number of days not at work.
Third, previous studies found contrasting results. Brown et al (1996) and Lydiard (1991) report that major depressive disorder comorbid with anxiety disorders (i.e. PTSD) is more severe than major depressive disorder alone in terms of depressive symptoms, course of illness and treatment response. Finally, even if PTSD does not cause additional disability above major depression, the diagnosis is still relevant for the correct choice of treatment.
REFERENCES
Brown, C., Schulberg, M. J., Madonia, M. J., et al (1996) Treatment outcomes for primary care patients with major depression and lifetime anxiety disorders. American Journal of Psychiatry, 153, 1293 -1300.[Abstract]
Lydiard, B. (1991) Coexisting depression and anxiety: special diagnostic and treatment issues. Journal of Clinical Psychiatry, 52, 48 -52.[Medline]
Neal, L. A., Green, G. & Turner, M. A.
(2004) Post-traumatic stress and disability.
British Journal of Psychiatry,
184, 247
-250.
King's College London, and Bristol Priory Hospital, Heath House Lane, Stapleton, Bristol BS16 1EQ, UK
The multivariate analysis of variance demonstrated no significant
difference between the group with DSM-IV PTSD and the group without DSM-IV
PTSD in terms of the severity of disability. This finding is unrelated to the
other mental health problems measured in the study, as shown by the analysis
of covariance. The power of the study was 0.85 (assuming a detectable
difference of 3 out of 30 on the Sheehan Disability Scale and =0.01).
This is acceptable for limiting the chances of type II error.
Multicollinearity is only of importance when trying to draw inferences about
the relative contribution of more than one predictor variable to the success
of the model. In this study the Beck Depression Inventory (BDI) (or its
variant the MBDI) was the only variable retained in the regression models and
so multicollinearity is not an issue. Disability is not an absolute
requirement in DSM-IV. The utility of objective measures of disability
v. subjective measures was discussed in the paper. However, the
subjective experience of the patient is probably of most value in clinical
terms. Other studies have found contrasting results, as discussed in the
paper's introduction. However, most have methodological limitations. The
treatment of PTSD, as opposed to depression, may be relevant to the DSM-IV
diagnostic criteria but may not be relevant to the patient.
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