Q J Med 2001; 94: 720-721
© 2001 Association of Physicians
Correspondence |
Depressive symptoms in injury and illness
Department of Psychology University of Newcastle upon Tyne, NE1 17RU, UK
Sir,
It is usually assumed in general medical practice that when a sick person develops a depressed mood, this is an understandable consequence of factors such as restricted physical activity and pain. An alternative perspective has been argued, which suggests that classical ‘depressive’ symptoms are often caused by activation of the immune system (especially cytokines such as interleukins, interferons and tumour necrosis factor, etc) which produces a state of malaise.1,2
Malaise comprises fatigue, heaviness, dull pains, aching of limbs and trunk, lack of energy and altered sleep patterns. These depressive symptoms seem to be the human equivalent of ‘sickness behaviour’ which is a stereotypical response of mammals suffering from infectious or inflammatory diseases.3 In other words, malaise is a behavioural pattern that is adaptive in acute infectious illnesses, ensuring that the animal will rest and conserve energy to mount an all-out immune attack on infective pathogens—depressive illness occurs when this syndrome is maladaptively severe or sustained.2
In a preliminary study, the relationship between poor health and depressive symptoms was investigated using the SF-36 and Beck Depression Inventory. The SF-36 is a well-validated 36-item health-status questionnaire, which provides an overall measure of general health and specific dimensions of health, including vitality, physical functioning, functional performance, pain and mental health.4 The Beck Depression Inventory (BDI) is a widely used self-administered scale to measure the severity of depressive symptoms using a 26-item questionnaire.5
Thirty-six subjects (17 male, 19 female) were studied in a convenience sample. There was a significant negative correlation between the SF-36 overall score (general health) and the score on the BDI, (correlation coefficient r=-0.611, p<0.001), confirming that depressive symptoms tend to occur with poor health. There were significant (p<0.05) correlations between the BDI score and SF-36 subscales for mental health (r=-0.707), physical health (r=-0.62), and vitality (r=0.662). However, there was no statistically significant correlation between the BDI score and subscales measuring physical functioning, limitations on activity due to physical problems, or bodily pain. This suggests that lowered mood cannot simply be explained as due to physical restriction and pain.
A further study compared depressive symptoms in two groups of subjects matched for severity of sickness: one group having systemic illnesses, and the other group having physical injuries. Nineteen physically injured subjects (11 males, 8 females), and 17 systemically ill subjects (6 males, 11 female) were studied from a convenience sample. Subjects with physical injuries comprised eight ligament, cartilage and muscle injuries; six with back and joint pain, and five with fractures and dislocations. Systemically ill subjects comprised 12 with symptoms of colds, flu, glandular fever and sore throats; eight with headaches; six with pyrexia and sweats; three with aches and pains; two with fatigue and four others (some subjects had more than one symptom).
The SF-36 overall health scores were not significantly different in the systemically ill and injured groups (Kruskal-Wallis test p>0.1). However, scores on the BDI were clearly distinct between the two groups. Among physically injured subjects, 84% scored 0–4 (‘no or minimal depression’); 11% scored 5–13 (‘mild depression’); and one outlier scored 15 (‘moderate depression’). By contrast, among systemically ill subjects, only 12% scored 0–4, while 88% scored 5–13 (‘mild depression’). The difference between the two groups was highly statistically significant (p<0.001, Kruskal-Wallis test).
These studies suggest that depressive symptoms are much commoner in systemic illness than physical injury of similar severity. This is consistent with the Malaise theory2 that depressive symptoms are more likely to be caused by immune activation than by physical restriction and pain. If the results are confirmed, one implication may be that depressive symptoms in systemically ill patients could be alleviated by treatment of the symptoms of malaise.
References
1. Hickie I, Lloyd A. Are cytokines associated with neuropsychiatric syndromes in humans? Int J Immunopharmacol1995; 17:677–83.[Medline]
2. Charlton BG. The malaise theory of depression: major depressive disorder is sickness behaviour and anti-depressants are analgesic. Med Hypotheses2000; 54:126–30.[Web of Science][Medline]
3. Hart Bl. Biological basis of the behaviour of sick animals. Neurosci Biobehav Rev1988; 12:123–37.[Web of Science][Medline]
4. Ware JE, Snow KK, Koninski M, Gandek B. SF-36 Health Survey: Manual and Interpretation Guide. Boston MA, New England Medical Centre, 1993.
5. Beck AT, Ward C, Mendelson M, et al. An inventory for measuring depression. Arch Gen Psychiat1961; 4:561–71.
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