Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Email this article to a Colleague Similar articles in this journal Alert me to new issues of the journal Add to My Articles & Searches Download to citation manager Citing Articles via Google Scholar Articles by Dickens, C. Search for Related Content Articles by Dickens, C. Other Childhood Disorders Syndromes Secondary to General Medical Disorders

Dr. Dickens Replies

TO THE EDITOR: There is no doubt that there is a significant association between pain and depression. This positive association has been demonstrated in numerous studies to date. We briefly reviewed this literature in our introduction and take no issue with this point, highlighted by Fishbain et al. in their comprehensive review of the literature. Interpreting statistical correlations as an indication of a direct (implying causal) link between pain and depression is incorrect, however.

The first problem with such an argument is that of the content validity of the measures of depression. The inclusion of biological symptoms of depression (e.g., sleep disturbance, loss of appetite) in such measures results in inflated depression scores, since these items can be endorsed by subjects as a result of their pain syndrome but attributed to a mood disturbance.¹ This problem with content validity acts to increase the apparent degree of association between pain and depression.

The second problem is that of the role of confounding or moderating (pathway) variables in influencing the association between pain and depression. Statistical correlations do not rule out the possibility that a significant association between variables is confounded or moderated by other variables, i.e., that the association of interest is indirect. Pain sufferers usually experience other associated physical, psychological, and social problems. All of these factors may contribute to the development of depression in pain sufferers, although most studies of the association between pain and depression fail to control adequately for the influence of these factors.

On the basis of our study of ambulant, chronic low back pain patients, we proposed a model in which the association between pain and depression is wholly moderated by degree of disability and illness attitude. This was the most parsimonious explanation for our data and highlights the complex interactions of physical and psychological factors in chronic pain populations. We do not suppose that our model is applicable to sufferers of pain of all degrees of severity or of all causes, which we indicated in our discussion. It is quite possible that pain is more strongly associated with depression in subjects with high degrees of pain but low levels of physical impairment.

We are not alone in our beliefs in the importance of confounding/moderating variables in the association between pain and depression. Dr. Fishbain and colleagues themselves found that five out of six studies examining the role of cognitive factors found them to significantly moderate the association between pain and depression. Von Korff et al. have confirmed that pain intensity failed to make an independent contribution to the levels of depression once the degree of pain-related disability was controlled.² In their review, Pincus and Williams urge us to move away from searching for direct causal pathways between pain and depression (pain causing depression or depression causing pain) and to develop more dynamic models which better describe the experiences of our patients.¹

These issues are not simply of academic interest. To best improve the quality of life of pain sufferers, it is crucial that we understand the relative importance of biological, psychological, and social factors in determining illness presentation.

REFERENCES

1. Pincus T, Williams A: Models and measurements of depression in chronic pain. J Psychosom Res 1999; 47:211-219[CrossRef][Medline]
2. Von Korff M, Ormel J, Katon W, Lin EH: Disability and depression among high utilizers of health care: a longitudinal analysis. Arch Gen Psychiatry 1992; 49:91-100[Abstract]

Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Email this article to a Colleague Similar articles in this journal Alert me to new issues of the journal Add to My Articles & Searches Download to citation manager Citing Articles via Google Scholar Articles by Dickens, C. Search for Related Content Articles by Dickens, C. Other Childhood Disorders Syndromes Secondary to General Medical Disorders

Get information about faster international access.

Privacy Policy

Copyright © 2002 Academy of Psychosomatic Medicine. All rights reserved.

Home | Search | Current Issue | Past Issues | Subscribe | All APPI Journals | Help | Contact Us