Abstract
Although much attention has been given to the physical determinants of common musculoskeletal complaints such as back and arm pain, research points to a stronger influence of psychological factors. Multiple studies have implicated poor mental health and somatisation (a tendency to worry about the common somatic symptoms) in the incidence and chronicity of musculoskeletal pain and associated disability. Also important are adverse beliefs about the prognosis of such disorders, and about the role of physical activity in their development and persistence. Differences in societal beliefs may have contributed to major variation in the prevalence of disabling musculoskeletal pain that has been observed between countries and in the same countries over time. Psychosocial aspects of work have also been linked with musculoskeletal pain, although relative risks have generally been smaller. There is a need to take account of psychological factors in the clinical management of patients with back, neck and arm pain.
Historically, attempts to prevent incapacity for work from musculoskeletal disorders have focused mainly on the physical demands of employment. It has been assumed that symptoms and disability arise from injury to tissues, and can be prevented by better ergonomic design of occupational tasks to reduce mechanical loading. This biophysical paradigm may be appropriate for some types of musculoskeletal disease – for example, osteoarthritis of the hip caused by heavy lifting (see Chapter X) and degenerative meniscal tears in the knee caused by prolonged kneeling and squatting (Chapter X). However, it has become increasingly apparent that the model has only limited applicability to common painful disorders of the back, neck and upper limb, which are the main musculoskeletal causes of disability for work.
Most disabling pain of the back and upper limb is non-specific in nature with no clear evidence of underlying injury to tissues, and even where pathology can be demonstrated (e.g., herniation of an intervertebral disc in people with back pain), it appears often not to be the explanation for the symptom . Furthermore, there have been major temporal changes in the prevalence of musculoskeletal illness and disability, which cannot be explained by altered physical exposures. For example, social security statistics indicate that in Britain, long-term incapacity for work because of back pain increased more than eightfold between 1950 and the early 1990s , at a time when the physical demands of work were declining because of greater mechanisation and a shift in employment from manufacturing to service industries. And in Australia, there was a major epidemic of arm pain during the 1980s among office workers, which was not paralleled in other countries that were using similar technology .
These observations indicate that factors other than mechanical loading have much greater impact on common disabling musculoskeletal disorders, and that they can vary importantly over time. Several lines of investigation have suggested that the drivers of the observed trends are psychosocial. This chapter considers the evidence implicating psychological and psychosocial influences in the causation of disabling musculoskeletal pain, and their potential to account for observed variations in its occurrence. It focuses in particular on the role of mental health, tendency to somatise, health beliefs and expectations, and psychosocial aspects of work. Implications for clinical practice and priorities for further research are highlighted.
Mental health
Definition
Mental health refers to emotional and psychological well-being , impairment of which may adversely affect an individual’s cognitive or social functioning, making it harder to cope with the demands of daily life, including, among other things, the ability to work productively and efficiently.
Problems with mental health range from the minor distress that all people experience at times in response to life’s challenges through to major long-term clinical illness that can be severely incapacitating and may require psychological therapy or pharmacological treatment. According to the biopsychosocial paradigm , common psychological symptoms, such as low mood, importantly influence the occurrence and prognosis of musculoskeletal pain.
Methods of assessment
In studies of musculoskeletal pain, mental health is generally assessed through questionnaires. Many have used questions derived from the 36-item Short Form Health Survey (SF-36) . This is a valid and reliable tool, designed for self-administration, which covers various aspects of health and quality of life, and has been translated into local languages in almost 50 different countries. It is made up of 36 items organised in eight scales, one of which (also known as Mental Health Inventory-5) concerns mental health. This comprises five questions about how much of the time during the past month individuals have been very nervous, felt so down in the dumps that nothing could cheer them up, felt calm and peaceful, felt downhearted and blue, and have been a happy person. Each of the five questions is rated on a five-point scale, ranging from ‘all of the time’ to ‘none of the time’. An overall measure can then be derived by assigning numerical scores to each answer (higher values indicating better mental health), and by summing across questions. This may be analysed as a continuous variable or partitioned into categories.
Other validated instruments that have been used to assess mental health include the Beck Depression Inventory (BDI) and the Patient Health Questionnaire (PHQ-9) . The BDI comprises 21 self-reported items, while the PHQ, which is the self-administered version of the Primary Care Evaluation of Mental Disorders (PRIME-MD) Questionnaire, scores the occurrence of the nine DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) diagnostic criteria for major depressive disorder.
Association with musculoskeletal illness
Poor mental health is more common in people with musculoskeletal pain, particularly when it is disabling . The relationship has been examined in several systematic reviews, which have indicated, for example, that depressive symptoms are related to higher levels of pain intensity, more functional limitation and disability, and worse prognosis , are strongly associated with knee pain and can predict the transition from acute to chronic low back pain and neck pain .
Cross-sectional associations with low mood may in part reflect distress that occurs as a consequence of pain. However, recent findings from longitudinal studies suggest that among individuals who are initially free from musculoskeletal pain, those with low mood are more likely subsequently to develop pain and associated disability ( Table 1 ). In addition, there is some evidence from experimental studies that induction of negative mood reduces pain tolerance and leads to higher levels of self-reported pain severity .
| Reference | Country | Study sample | Duration of follow-up | Exposures compared | Pain outcome | Risk estimate (95% CI) | Adjustment for confounders |
|---|---|---|---|---|---|---|---|
| Smedley et al., 1997 | UK | 961 nurses initially free from LBP for ≥1 month | 1.5 years (mean) | Report of frequent versus none or occasional low mood | Incident low back pain leading to absence from work | OR: 3.4 (1.4–8.2) | Age, height, history low back pain and report of headache, period pain, fatigue, stress |
| Miranda et al., 2001 | Finland | 2094 forestry workers initially free from shoulder pain for ≥12 months | 1 year | Mental stress: rather much or much versus not at all | Incident shoulder pain | OR: 1.9 (1.1–3.3) | Age, sex, body mass index, work-related tasks and leisure-time physical activity |
| Elliott et al., 2002 | UK | 852 adults from general population, who initially were free from chronic pain | 4 years | Lowest quartile of SF-36 mental health scores versus other | Chronic pain at follow-up | OR:1.6 (1.2–2.2) | None |
| Eriksen et al., 2004 | Denmark | 2292 adults from general population, who initially were free from moderate or worse pain | 6 years | Poor versus good SF-36 mental health | Moderate or worse pain at follow-up | OR: 3.3 (2.5–5.0) a | Age and sex |
| Smith et al., 2004 | UK | 1219 adults from general population, who initially were free from chronic back pain | 4 years | Lowest quartile of SF-36 mental health scores versus other | Chronic back pain at follow-up | OR: 2.0 (1.5–2.7) | None |
| Palmer et al., 2007 | UK | 788 adults from general population, who initially had been free from knee pain for >12 months | 1.5 years | Worst versus best third of SF-36 mental health scores | Knee pain in the past 4 weeks at follow-up | OR: 1.4 (0.9–2.3) | Age, sex and general practice |
| Palmer et al., 2008 | UK | 613 adults from general population, who initially had been free from arm pain for >12 months | 1.5 years | Worst versus best third of SF-36 mental health scores | Arm pain in the past 4 weeks at follow-up | OR: 1.7 (1.1–2.8) | Age, sex and general practice |
| Solidaki et al., 2013 | Greece | 168 nurses, postal clerks and office workers, with pain at <2/6 anatomical sites in the past 12 months at baseline | 1 year | Worst versus best third of SF-36 mental health scores | Pain at ≥2/6 anatomical sites in the past month at follow-up | OR: 1.5 (0.5–4.9) | Age, sex and occupation |
| Sadeghian et al., 2013 | Iran | 245 nurses and office workers, who initially had no neck or shoulder pain in the past month | 1 year | Worst versus best third of SF-36 mental health scores | Neck or shoulder pain in the past month at follow-up | PRR: 1.8 (1.0–3.0) | Age, sex, occupational physical activity, psychosocial aspects of work and somatising tendency |
| Sadeghian et al., 2014 | Iran | 385 nurses and office workers | 1 year | Worst versus best third of SF-36 mental health scores | Low back pain in the past month at follow-up | PRR: 1.3 (0.9–1.7) | Age, sex, occupation, occupational lifting, psychosocial aspects of work, somatising tendency, beliefs about back pain, history of low back pain at baseline |
| Vargas-Prada et al., 2013 | Spain | 971 nurses and office workers | 1 year | Worst versus best third of SF-36 mental health scores | Disabling pain in the past month at follow-up at an anatomical site which was free from pain in the past month at baseline | OR: 1.5 (1.0–2.3) | Age, sex, occupation, pain at the same anatomical site in the year before baseline, occupational physical activity, job satisfaction, somatising tendency and adverse beliefs |
| Vargas-Prada et al., 2013 | Spain | 579 nurses and office workers with no low back pain in the past month at baseline | 1 year | Worst versus best third of SF-36 mental health scores | Disabling low back pain in the past month at follow-up | PRR: 1.9 (0.9–4.0) | Age, sex, occupation, occupational lifting, adverse beliefs, somatising tendency, smoking, low back pain in the past year at baseline |
| Vargas-Prada et al., 2014 | Spain | 971 nurses and office workers | 1 year | Worst versus best third of SF-36 mental health scores | Pain in the past month at follow-up at an anatomical site in the upper limb which was free from pain in the past month at baseline | OR: 1.4 (1.0–1.9) | Age, sex and occupation |
a Published risk estimate was for good versus poor mental health, and this has been inverted to be consistent with estimates from other studies.
Some investigators have looked for biological mechanisms that might explain the link between low mood and musculoskeletal pain, including the possible role of neurotransmitters and cytokine receptors . However, there is still no established neurochemical explanation for the association. It could also occur because some people are generally more aware of symptoms, and predisposed to report them, whether they are mental or physical in nature. As an extension of this, it is also possible that individuals who experience low mood tend to worry about their health, give more attention to pain and as a consequence are more inclined to avoid activities that exacerbate their symptoms, thus inhibiting recovery .
Conclusions
Although the causal pathways linking mental health with musculoskeletal pain have yet to be fully elucidated, it is evident that low mood influences both the occurrence and persistence of pain symptoms. Moreover, its impact on the disability that arises from musculoskeletal pain appears to be even greater . This suggests a need to assess mental health in patients presenting to medical care because of musculoskeletal pain. Those with low mood are at a greater risk of poor outcomes, and they may benefit from more intensive management, including the treatment of their depression if it is of sufficient severity.
Somatising tendency
Definition
Somatising tendency is a predisposition to be more aware of, and to worry about, common somatic symptoms. It is characterised by (i) a constant scanning of the environment for threats (hypervigilance), (ii) a tendency to focus on certain relatively weak and infrequent body sensations and (iii) a predisposition to intensify somatic sensations, making them more alarming, noxious and disturbing . Compared to others, individuals with a high tendency to somatise have been found to report impaired social and occupational functioning , to make greater demands on medical care , and to be less satisfied with the care that they receive .
Methods of assessment
Tendency to somatise is normally assessed through questionnaires. For example, the Brief Symptom Inventory (BSI) , which is a shortened form of the Symptom Checklist-90 Revised (SCL-90-R), includes a section relating to ‘somatisation’. This comprises seven questions covering general (‘faintness or dizziness’ and ‘hot or cold spells’), cardiovascular (‘pains in the heart or chest’), respiratory (‘trouble getting your breath’), gastrointestinal (‘nausea or upset stomach’) and neuromuscular (‘numbness or tingling in parts of your body’ and ‘feeling weak in parts of your body’) symptoms during the past week. Each item is rated on a five-point scale of distress, ranging from ‘not at all’ to ‘extremely’, and individuals can be classified by assigning scores to each answer and summing across questions , or simply by counting the number of symptoms that have caused distress above a specified threshold (e.g., at least moderately distressing) . In studies of associations with musculoskeletal illness, the questions relating to neuromuscular symptoms may be omitted as they could be a direct consequence of musculoskeletal pathology. The BSI has been translated into several languages, and it is a validated and reliable tool .
Other questionnaires that have been used to ascertain somatising tendency include the General Health Questionnaire (GHQ) , the Modified Somatic Perception Questionnaire (MSPQ) and the Somatic Symptom Scale (SSS-8) . The GHQ is available in versions of 12, 28, 30 and 60 items, and it has been tested as a screening tool for the assessment of short-term distressing somatic symptoms . The MSPQ has 13 items (each of which is scored on a four-point scale), and the SSS-8 has eight items (each scored on a five-point scale).
Association with musculoskeletal illness
There is now strong evidence that somatising tendency is importantly associated with common musculoskeletal disorders such as back and arm pain. Many of the relevant studies have been cross-sectional in design , and these have found relative risks or odds ratios (ORs) of up to 4–5 for pain at specific anatomical sites. Moreover, the relationship extends to widespread pain , and there are indications that relative risks are even higher for pain occurring at multiple sites . In particular, a large international study, which compared associations with risk factors for different patterns of musculoskeletal pain, found that relative to no pain, pain that affected six or more anatomical sites showed a stronger association with tendency to somatise than pain involving fewer than four anatomical sites .
Importantly, the relationship is not only with awareness and reporting of musculoskeletal symptoms but also with disability for everyday activities as a consequence of musculoskeletal pain .
It is possible that the development of a musculoskeletal disorder could sensitise an individual to other symptoms. However, findings from longitudinal studies suggest that causation is in the reverse direction – that is, that people with somatising tendency are more prone to develop musculoskeletal pain and associated disability. Thus, among subjects who initially were free from pain, higher scores for somatisation have predicted future incidence ( Table 2 ). Again, associations have applied to disabling pain as well as to self-reported pain. Moreover, in community-based and workforce-based studies, the prevalence of somatising tendency sufficient to carry an important increase in the risk of disabling pain has been substantial (∼10–20%) .
| Reference | Country | Study sample | Duration of follow-up | Exposures compared | Pain outcome | Risk estimate (95% CI) | Adjustment for confounders |
|---|---|---|---|---|---|---|---|
| Macfarlane et al., 2000 | UK | 1260 adults from general population, who initially were free from forearm pain | 2 years | 2–5 versus 0 symptoms from somatic symptom scale | Forearm pain in the past month at follow-up | RR: 1.7 (1.0–3.0) | Age and sex |
| Palmer et al., 2007 | UK | 788 adults from general population, who initially had been free from knee pain for >12 months | 1.5 years | Worst versus best third of somatising scores derived from BSI questions | Knee pain in the past 4 weeks at follow-up | OR: 1.6 (1.0–2.7) | Age, sex and general practice |
| Palmer et al., 2008 | UK | 613 adults from general population, who initially had been free from arm pain for >12 months | 1.5 years | Worst versus best third of somatising scores derived from BSI questions | Arm pain in the past 4 weeks at follow-up | OR: 2.0 (1.2–3.4) | Age, sex and general practice |
| Solidaki et al., 2013 | Greece | 168 nurses, postal clerks and office workers, with pain at <2/6 anatomical sites in the past 12 months at baseline | 1 year | ≥2 versus 0 somatic symptoms at least moderately distressing in the past week | Pain at ≥2/6 anatomical sites in the past month at follow-up | OR: 1.8 (0.5–5.7) | Age, sex and occupation |
| Sadeghian et al., 2013 | Iran | 245 nurses and office workers, who initially had no neck or shoulder pain in the past month | 1 year | ≥2 versus 0 somatic symptoms at least moderately distressing in the past week | Neck or shoulder pain in the past month at follow-up | PRR: 1.2 (0.8–1.8) | Age, sex, occupational, physical activity, psychosocial aspects of work and mental health |
| Sadeghian et al., 2014 | Iran | 385 nurses and office workers | 1 year | ≥2 versus 0 somatic symptoms at least moderately distressing in the past week | Low back pain in the past month at follow-up | PRR: 1.1 (0.9–1.4) | Age, sex, occupation, occupational lifting, psychosocial aspects of work, mental health, beliefs about back pain, history of low back pain at baseline |
| Vargas-Prada et al., 2013 | Spain | 971 nurses and office workers | 1 year | ≥2 versus 0 somatic symptoms at least moderately distressing in the past week | Disabling pain in the past month at follow-up at an anatomical site which was free from pain in the past month at baseline | OR: 3.5 (2.2–5.6) | Age, sex, occupation, pain at the same anatomical site in the year before baseline, occupational physical activity, job satisfaction, mental health and adverse beliefs |
| Vargas-Prada et al., 2013 | Spain | 579 nurses and office workers with no low back pain in the past month at baseline | 1 year | ≥2 versus 0 somatic symptoms at least moderately distressing in the past week | Disabling low back pain in the past month at follow-up | PRR: 1.4 (0.7–3.0) | Age, sex, occupation, occupational lifting, adverse beliefs, mental health, smoking, low back pain in the past year at baseline |
| Vargas-Prada et al., 2014 | Spain | 971 nurses and office workers | 1 year | ≥2 versus 0 somatic symptoms at least moderately distressing in the past week | Pain in the past month at follow-up at an anatomical site in the upper limb which was free from pain in the past month at baseline | OR: 2.2 (1.6–3.1) | Age, sex and occupation |
An effect of somatising tendency on the development of non-specific musculoskeletal disorders is mechanistically plausible. Transient pain can be expected to occur quite frequently because of everyday physical strains or minor external trauma, but in a person who is predisposed to notice and worry about somatic symptoms, the sensation may be amplified and become more persistent. Systematic reviews of longitudinal studies have concluded that, as with poor mental health, somatising tendency is importantly implicated in the transition from acute to chronic musculoskeletal pain .
Interestingly, there are indications that the relationship to somatising tendency is weaker for musculoskeletal disorders with clear underlying pathology. Thus, in a case–control study of patients presenting for neurophysiological investigation because of suspected carpal tunnel syndrome, somatising tendency was less frequent in those with confirmed impairment of median nerve conduction than in those whose nerve conduction was normal (OR: 0.6; 95% confidence interval (CI): 0.4–0.9) .
Conclusions
It is clear that somatising tendency contributes importantly to the overall burden of non-specific musculoskeletal illness and associated disability. Therapeutic interventions aimed at reducing the tendency to somatise have been disappointing . However, it is possible that its effects are modified by other risk factors, which are more amenable to alteration, and as a first step, it would be useful to understand better the interactions between somatising tendency and other causes of common musculoskeletal disorders.
In clinical practice, a tendency to somatise suggests a worse prognosis in patients presenting with musculoskeletal pain, and this may indicate a need for more intensive management.
Somatising tendency
Definition
Somatising tendency is a predisposition to be more aware of, and to worry about, common somatic symptoms. It is characterised by (i) a constant scanning of the environment for threats (hypervigilance), (ii) a tendency to focus on certain relatively weak and infrequent body sensations and (iii) a predisposition to intensify somatic sensations, making them more alarming, noxious and disturbing . Compared to others, individuals with a high tendency to somatise have been found to report impaired social and occupational functioning , to make greater demands on medical care , and to be less satisfied with the care that they receive .
Methods of assessment
Tendency to somatise is normally assessed through questionnaires. For example, the Brief Symptom Inventory (BSI) , which is a shortened form of the Symptom Checklist-90 Revised (SCL-90-R), includes a section relating to ‘somatisation’. This comprises seven questions covering general (‘faintness or dizziness’ and ‘hot or cold spells’), cardiovascular (‘pains in the heart or chest’), respiratory (‘trouble getting your breath’), gastrointestinal (‘nausea or upset stomach’) and neuromuscular (‘numbness or tingling in parts of your body’ and ‘feeling weak in parts of your body’) symptoms during the past week. Each item is rated on a five-point scale of distress, ranging from ‘not at all’ to ‘extremely’, and individuals can be classified by assigning scores to each answer and summing across questions , or simply by counting the number of symptoms that have caused distress above a specified threshold (e.g., at least moderately distressing) . In studies of associations with musculoskeletal illness, the questions relating to neuromuscular symptoms may be omitted as they could be a direct consequence of musculoskeletal pathology. The BSI has been translated into several languages, and it is a validated and reliable tool .
Other questionnaires that have been used to ascertain somatising tendency include the General Health Questionnaire (GHQ) , the Modified Somatic Perception Questionnaire (MSPQ) and the Somatic Symptom Scale (SSS-8) . The GHQ is available in versions of 12, 28, 30 and 60 items, and it has been tested as a screening tool for the assessment of short-term distressing somatic symptoms . The MSPQ has 13 items (each of which is scored on a four-point scale), and the SSS-8 has eight items (each scored on a five-point scale).
Association with musculoskeletal illness
There is now strong evidence that somatising tendency is importantly associated with common musculoskeletal disorders such as back and arm pain. Many of the relevant studies have been cross-sectional in design , and these have found relative risks or odds ratios (ORs) of up to 4–5 for pain at specific anatomical sites. Moreover, the relationship extends to widespread pain , and there are indications that relative risks are even higher for pain occurring at multiple sites . In particular, a large international study, which compared associations with risk factors for different patterns of musculoskeletal pain, found that relative to no pain, pain that affected six or more anatomical sites showed a stronger association with tendency to somatise than pain involving fewer than four anatomical sites .
Importantly, the relationship is not only with awareness and reporting of musculoskeletal symptoms but also with disability for everyday activities as a consequence of musculoskeletal pain .
It is possible that the development of a musculoskeletal disorder could sensitise an individual to other symptoms. However, findings from longitudinal studies suggest that causation is in the reverse direction – that is, that people with somatising tendency are more prone to develop musculoskeletal pain and associated disability. Thus, among subjects who initially were free from pain, higher scores for somatisation have predicted future incidence ( Table 2 ). Again, associations have applied to disabling pain as well as to self-reported pain. Moreover, in community-based and workforce-based studies, the prevalence of somatising tendency sufficient to carry an important increase in the risk of disabling pain has been substantial (∼10–20%) .
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