In the US alone, back and neck problems are the leading cause of work-related disability, costing more than $50 billion each year [1]. Workplace injuries related to musculoskeletal pain are a particular and persistent problem for nursing personnel as evidenced by the large number of lost work time in this sector [2]. Still, workplace injuries only reflect parts of the problem since injury incidence rates are an incomplete measure of the extent of work-related back pain. There are several reasons for this, including restrictions on what constitutes an injury case, reluctance to file injury claim due to fear of employment repercussions, and health care worker conditioning to ignore back pain [3–6]. Symptom surveys examining participants own reports of back pain as well as pain interference with work may therefore be a better indication of the extent of this problem.

Musculoskeletal pain is commonly associated with psychological distress, particularly depression [7–9]. Different hypotheses have been suggested to explain the association between the two, including the following three; 1) psychological distress increases the risk of pain (antecedent hypothesis), 2) pain increases the risk of psychological distress (consequences hypothesis), and 3) a common mechanism influences the development of both chronic pain and psychological distress (common pathogenetic mechanism). A longitudinal study of low back pain (LBP) patients in primary care showed that LBP and psychological distress were associated both cross-sectionally and longitudinally, suggesting there might be multiple mechanisms linking pain and psychological distress [8]. Assuming no residual confounding, there seems to be support for all three hypotheses. Further, there seems to be an interesting difference between upper- and lower body pain conditions regarding psychological distress. For instance, LBP has been found to be associated with higher levels of psychological distress than shoulder pain [10], and the same differences have been found between LBP and neck pain, where persons with LBP are more likely to suffer from psychological distress and serious mental illness than persons with neck pain [9].

Co-morbid psychological distress in workers with musculoskeletal pain could have important implications from an injury and disability prevention perspective. Given that psychological distress has been found to be a powerful prognostic factor in recovery from musculoskeletal pain [11–15], it may need to be specifically targeted to prevent further disability-related to injuries involving pain. Knowledge about the associations between psychological distress, musculoskeletal pain, and interference with work could therefore help inform the design of future health promotion and disability prevention interventions aimed at both primary and secondary prevention.

The health care sector seems to be slightly different than other sectors when it comes to workers’ health. In the US, patient care workers have one of the highest musculoskeletal injury and illness rates among all three-digit Standardized Industrial Classification codes [2], and besides an increased risk of musculoskeletal disorders, nursing personnel also have a higher risk of blood-borne infections and occupational allergies [16]. The increased risk of work-related injuries in patient care workers has been related to the nature of their work, involving frequent exposure to biological, chemical, physical and psychosocial hazards [17]. Previous studies have mostly been focused around the physical risk factors for musculoskeletal injuries, but recent studies indicate that psychosocial factors may be even more important risk factors of pain and disability in patient care workers [18–20].

Despite the many studies associating pain with distress, no studies have looked specifically at the co-occurrence of musculoskeletal pain and psychological distress in a health care setting, and whether the psychological distress is independently related to interference with work or number of pain areas. The aims of this study were to use data from a survey of health care workers to assess the association of psychological distress and musculoskeletal pain, how it is related to pain interference with work and multiple pain areas, and potential differences between the different pain areas. We hypothesized that psychological distress would be independently associated with pain interference with work, and more so for workers with lower body pain compared to upper body pain.

In this study, we found that patient care workers who reported any musculoskeletal pain during the last 3 months, also showed significantly more psychological distress compared with those who did not report any pain. Psychological distress was significantly associated with pain interference with work, even after adjusting for pain and demographics. The association was stronger for those with lower body pain or both upper- and lower body pain, with the strongest association presenting in the group with pain in both places. The workers with both upper and lower body pain also reported significantly more psychological distress than other workers. Finally, psychological distress was also independently associated with multiple pain areas. Thus, psychological distress seems to be more prevalent in workers with musculoskeletal pain, and more so for workers with both upper and lower body pain. The distress further seems to be independently associated with pain interference with work as well as multiple pain areas.

When psychological distress was analyzed separately for each response alternative of the “pain interference with work” variable, one response category appeared to identify a particularly disabled and distressed group. Generally, the responses showed a linear relationship between higher interference with work and higher levels of psychological distress, except for the most extreme category, which somewhat surprisingly showed lower levels of psychological distress compared to the two previous categories. The most work-disabled and distressed group was therefore those in the next highest category, reporting that the pain interfered “quite a bit” with their ability to work. When comparing this group to the group in the highest category (extreme interference) the former was found to report higher pain comorbidity in terms of more pain areas. This is in line with the overall results of the study and could potentially account for these findings.

Few, if any, previous studies have looked specifically at psychological distress in relation to musculoskeletal pain in hospital patient care workers, but our findings do compare with previous findings of psychosocial factors and musculoskeletal pain in health care workers. Expectations about pain duration and fear-avoidance beliefs were both important psychosocial factors associated with long duration pain in a study of community health care workers [20], and a stressful psychosocial work environment was found to be significantly associated with both upper body injuries [25] and back or neck-pain-related disability in nursing staff [18]. In hospital workers in general, work-related musculoskeletal pain is more strongly influenced by specific psychosocial and physical job-related exposures than by broad socioeconomic factors such as education and income [26]. Among nurses’ aides, not only mechanical exposure, but also organizational, psychological and social work factors increase the risk of low back symptoms [19]. The study by Simon et al [18] is of particular interest as it compares a large number of nursing staff from seven different countries. The findings show a pronounced relationship between psychosocial factors and back or neck-pain-related disability, and the association is much higher for psychosocial than for physical factors [18]. This leaves little doubt that psychosocial factors are important for musculoskeletal pain and disability. Given the close relationship, both conceptually and empirically, between psychosocial work stress and psychological distress [27], our findings seem to be in concordance with these previous studies.

Possible implications of our findings could involve targeted interventions for workers with persistent pain and concurrent psychological distress. The elevated level of psychological distress in some of the workers could be an indication of poor pain management. A number of different studies over the last 20–30 years have demonstrated that behavioral and psychosocial protocols are beneficial for patients with persistent pain [28], including management of LBP [29–31], arthritis pain [32, 33], cancer pain [34, 35], tension and migraine headache [36], and mixed chronic pain syndromes [37]. Offering some kind of behavioral or psychosocial intervention to help patient care workers cope with the pain, could therefore help reduce psychological distress and possibly also prevent future disability. Even if the degree of psychological distress was far from any clinical diagnostic levels in most of the workers, it could still represent a risk factor for future disability as seen in other studies from working populations [15]. The workers with both upper and lower body pain showed a particularly high level of psychological distress that influenced their ability to work. It is possible that the wide specter of hazards these workers are exposed to make them particularly sensitive for developing vicious circles of pain and disability. Further research is needed to look more in to the specific risks of the workers in this sector. Given the wide specter of hazards we know them to be exposed to, it seems important that the psychological dimension as well as the physical and environmental dimensions also be considered in the design and refinement of future workplace interventions.

The study has some limitations that need to be considered. As for the elevated levels of psychological distress, the magnitudes of the odds ratios we found to be statistically significant may not have corresponding clinical relevance. Still, we would argue that even small changes in the risk could have important public health implications at the population level [38], and even more so for such a costly and prevalent problem as musculoskeletal pain. The generalizability of the results could further be questioned as they are all based on data collected from two academic teaching hospitals in the greater Boston area, and self-report results are always vulnerable for recall and social-desirability bias. Still, the study has an important strength worth noting, which is the high response rate to the survey (79%). The findings rely on cross-sectional data, and as with any cross-sectional studies, it is not possible to draw any conclusions regarding causality or direction of associations. One direction for future research could therefore be to investigate these associations with longitudinal data to see whether psychological distress is a risk factor for work-related injuries in patient care workers, and if number of pain areas and location influence the potential risk in any way.

In a study of mostly White, female hospital patient care workers, psychological distress was higher in workers with musculoskeletal pain, and highest among workers with both upper and lower body pain. Distress further seemed to be significantly associated with pain interference with work as well as number of pain areas. These findings may be followed up with a longitudinal design to better determine the direction of the associations, and to investigate if psychological distress increases the risk of work disability and injuries.