Study Design. A systematic review of observational studies.
Objectives. To assess whether psychosocial factors at work and in private life are risk factors for the occurrence of back pain.
Summary of Background Data. Several reviews on risk factors for back pain have paid attention to psychosocial factors. However, in none of the published reviews was a strict systematic approach used to identify and summarize the available evidence.
Methods. A computerized bibliographical search of several databases was performed, restricted to studies with a cohort or case-control design. A rating system was used to assess the strength of the evidence for various factors, based on the methodologic quality of the studies and the consistency of the findings.
Results. Eleven cohort and two case-control studies were included in this review. Strong evidence was found for low social support in the workplace and low job satisfaction as risk factors for back pain. Insufficient evidence was found for an effect of a high work pace, high qualitative demands, low job content, low job control, and psychosocial factors in private life.
Conclusions. Evidence was found for an effect of low workplace social support and low job satisfaction. However, the result for workplace social support was sensitive to slight changes in the rating system, and the effect found for low job satisfaction may be a result of insufficient adjustment for psychosocial work characteristics and physical load at work. In addition, the combined evaluation of job content and job control, both aspects of decision latitude, led to strong evidence of a role for low job decision latitude. Thus, based on this review, there is evidence for an effect of work-related psychosocial factors, but the evidence for the role of specific factors has not been established yet.
Back pain and other musculoskeletal symptoms are a major health problem in the Western world. Musculoskeletal disorders have been shown to be the largest group of occupational diseases in studies in different countries. 40 Figures of the British Occupational Physicians Reporting Activity show that of all new cases of diseases reported by occupational physicians in 1996 and 1997 nearly one half were musculoskeletal disorders. 28 According to the World Health Organization definition a work-related disorder is multifactorial, which indicates the role of physical, organizational, psychosocial, and sociologic factors in its development. 67 In occupational health research there has been an increasing interest in psychosocial factors at work during the past few years.
Four explanations for the association between psychosocial work characteristics and musculoskeletal symptoms have been suggested. First, psychosocial work characteristics can directly influence the biomechanical load through changes in posture, movement and exerted forces. 25,61,63 Second, these factors may trigger physiologic mechanisms, such as increased muscle tension or increased hormonal excretion, that may in the long term lead to organic changes and the development or intensification of musculoskeletal symptoms or may influence pain perception and thus increase symptoms. 23,25,61,63 Third, psychosocial factors may change the ability of an individual to cope with an illness which, in turn, could influence the reporting of musculoskeletal symptoms. 23,25,61,63 Fourth, the association may well be confounded by the effect of physical factors at work. 23,25,61,63 It seems plausible that psychosocial factors in private life could also affect musculoskeletal symptoms through the second and third mechanism.
In this article, the authors examine the evidence for psychosocial factors at work and in private life as risk factors for back pain. Several reviews on risk factors for back pain have paid attention to psychosocial factors. 9,23-25,27,30 However, none of the published reviews included clearly defined inclusion and exclusion criteria, a methodologic quality assessment of the studies, as well as explicit criteria on which the assessment of the strength of the evidence was based. In this review a strict systematic approach is used to identify and summarize the available evidence in the literature. The method used is comparable with that applied in the clinical literature regarding the efficacy of interventions for back pain. 65 In this field, the current interest in evidence-based medicine has led to an extensive increase in the publication of systematic reviews and to the development of methodologic guidelines for systematic reviews. 64
Because individual psychological factors such as personality traits and cognitive and behavioral variables are also referred to as psychosocial factors, it is important to emphasize that this review concentrates only on psychosocial factors at work and in private life. The grouping of psychosocial work characteristics into categories in this review is mainly based on the demand-control-support model, developed by Karasek et al 36,39 and Johnson and Hall. 35 Although it is questionable whether job satisfaction should be regarded as a separate psychosocial work characteristic or as a response to working conditions such as psychosocial work characteristics and physical load at work, job satisfaction is included because many of the studies on work-related psychosocial factors as risk factors for back pain that have been performed so far focused on job dissatisfaction.
In this article, a systematic approach was applied to answer the following research questions: Are psychosocial factors at work risk factors for the occurrence of back pain? Are psychosocial factors in private life risk factors for the occurrence of back pain? A similar evaluation of the evidence for aspects of physical load as risk factors for back pain has been reported elsewhere. 34