Last updated: Mon, Nov 4, 2024
There is much interest among some researchers and practitioners in “somatization,” in which emotional or psychological distress is thought to be experienced or described as bodily (somatic) pain. There will be more discussion about the general idea of somatization in a following section (Somatization, Psychogenic Pain, and So Forth), but here I wish to describe an epidemiologic study that looked into related ideas. The study, conducted in the North of England in the early 2000s, examined 800-odd workers who had recently started one of several entry-level jobs, mostly in the public and service sectors, which are known to have a high prevalence of musculoskeletal disorders. The workers were mostly in their early to mid-twenties and were beginning their first full-time jobs.
They were asked to complete a questionnaire at two times about one year apart. The first questionnaire was completed an average of eight months into the new job, the second about a year later. The subjects were asked on each occasion whether they had experienced pain for at least 24 hours in any of four locations (lower back, shoulders, knees, forearms). The answers were analyzed to find connections between “exposures,” which in actuality were reports of psychic distress, and outcomes, or reports of pain.
The exposures included answers to the following questions:
In each case the answers were multiple-choice.
The results showed that workers who indicated psychic stress (dissatisfied, bored, too fast, etc.) were more likely to report pain (up to twice as likely) than those workers who didn't. The location of pain (back, shoulders, knees, forearms) wasn't consistently related to the job. The size of the relations was much too large to be explained by chance considering the number of subjects, so something significant is going on. What is it?
The authors concluded that in cohorts [related groups] of newly employed workers, certain work related psychosocial factors and individual psychological distress are associated with the subsequent reporting of musculoskeletal pain, and generally this effect is common across anatomical sites.
1
So far, so good. The term "associated" is a relatively broad one and the researchers are so far on firm ground. However, they go on to say that their study has shown that adverse psychosocial factors and psychological distress do predict future reported pain and that their effect is largely similar across anatomical site.
2
There are two problems with this latter statement. The first is that the answers to the seven questions are neither more nor less than that: they are the answers to those seven questions. While the authors may intend them to reflect what they and we may mean by the phrase adverse psychosocial factors and psychological distress,
the burden is clearly on the researchers to demonstrate that is the case. In reality, the questions simply ask the respondents for their impression of their worklife. The experiment provides no way to distinguish the respondents' perceptions from the reality of their workworld. The second problem with the statement is the term predict.
In reality the data analysis doesn't distinguish between "exposures" that were reported at the time of the first questionnaire and those reported on the second. This is a strange use of the word "to predict," and is very much like what we mean if we say "is correlated to."
The facts of the study, but not the author's second characterization of them, support an alternative explanation: People who are in pain see the world as more adverse. The researchers repeat their bias in their discussion of related results. They report that [a]nother study found that among 902 blue and white collar workers at an engineering company, psychosocial factors were associated with symptoms throughout the body and concluded that there was a general musculoskeletal sensitivity to mental stress.
3
There may indeed be such a sensitivity. It is certainly taken for granted in much published literature. However, the practical difference between pain caused by stress on the one hand and stress caused by pain on the other is important enough that the distinction shouldn't be assumed or verbalized away. It seems to me that the authors of this study have made the apparently-common error of trying to create strong conclusions from a weak experimental design.