Various studies have confirmed the prevalence of depression among chronic pain patients, with 50% to 65% of them typically being diagnosed as depressed. It has been shown that depressed chronic pain patients are less likely to respond to treatment for their pain, and that among low-back pain patients, it is the depressed ones who are most likely to avoid physical activity. It is also possible that depressed patients feel their pain more severely than others. All of this means that depression signals a worse prognosis for a chronic pain patient.
Since pain is harder to treat than depression, antidepressive therapy is often the best first step on the road to curing chronic pain. Numerous attempts have been made to produce a model capable of predicting the chances of depression in chronic pain patients, but results have generally been equivocal or contradictory. This study tried to do the same, looking at a wide range of demographic, pain-related, and work-related criteria.
The basic sample under study consisted of 254 patients who had all experienced chronic pain for at least six months. Their average age was 40, and the average duration of their pain was five years. Two-thirds were unemployed, while one-third were receiving compensation for work-related injuries. Two-thirds were married and two-thirds were white, with women comprising fractionally over half of the study population. A quarter were involved in litigation while a further third planned it.
Depression was evaluated according to the Beck Depression Inventory, a standard tool for 30 years. This questionnaire contains 21 symptoms and asks patients to rate the severity of each on a scale of one to four, by choosing the statement that best represents their experience of that symptom. It has been shown in the past to be a valid method of measuring depression in chronic pain patients. The average score of the 254 patients was 15.82 out of a possible 63, with the least depressed scoring seven and the most depressed 50.
The strongest single predictor of depression was work status. Consistent with previous findings in healthy as well as chronic pain patients, it was found that employment is important to the average adult’s self-esteem, and lack of a job made depression considerably more likely.
Among unemployed patients, the prospect of litigating over their injury was a great consolation, but the benefit wore off once the process actually had to be confronted. Among working patients, the effect was the opposite — it was those considering or pursuing litigation against their employers who were most likely to be unhappy. This may be because of the awkward position in which they found themselves as employees, or merely due, as the authors speculate, to the contradiction inherent in working while suing the company.
After work status, the factor that correlated most clearly with depression was the patient’s level of education. Those with less schooling were notably more vulnerable to depression. This may be due to the greater likelihood that their employment had been of a physical nature, and therefore was more likely to be affected by injury and subsequent pain. Many of the less well-educated patients lived in small towns where the alternatives available to them were more limited. Finally, the authors suggest that a less flexible way of thinking may cause poorly-educated people to overlook alternatives and ways of coping that others might have seen.
The unmarried were less able to cope with their suffering than those who had a partner to lean on. Again, this is a common finding in depression studies, but its validity here is somewhat weakened by the fact that the divorced, widowed and cohabiting were lumped together in the “single” group. As a rule, cohabitors are happier than other single people, while divorcees and the recently widowed tend to be the most depressed.
Ethnicity was found to bear no relation to stress, although, again, the findings might have been different if the study had distinguished between different categories of nonwhite. Small sample size, however, precluded this refinement.
Comparisons of age and gender led to what are probably the most interesting results to come out of this survey. It was found that among women, depression declined with age, while among men it worsened. Thus, among those under 40, women were most affected, but among those older than this it was men who had the highest Beck scores. This is not at all a common finding in depression studies not looking at chronic pain sufferers. No obvious reason for this trend presents itself.
As for the degree and duration of the pain itself, this had remarkably little effect on the patients’ mental state. The number of surgical interventions undergone, the number of drugs being taken for pain, and the subjective assessment of suffering on a one-to-10 point scale were all found to bear no significant correlation to patient depression. Only the overall duration of the chronic pain was found to have an effect, with long-term patients the most depressed. This effect, too, was less pronounced than many demographic factors.
At the end of the day, this survey provides a rough guide to the sort of patients most likely to be emotionally laid low by injury, but the small size of the sample and the difficulty in separating various risk factors means there is still more research needed in this area, particularly as some of these findings contradict previous studies in the same area. The authors are at pains to acknowledge that there is nothing in this study which removes the need to make assessments of depression, in chronic pain patients as in anybody else, on a firmly individual basis.