Link between stress and musculoskeletal disorders

In 2005-06, 1,958,000 people in the UK reported suffering from an illness that was caused or made worse by their current or past work. Of these, 52% reported musculoskeletal disorders (MSDs), and 21% reported stress, depression or anxiety.

In terms of the 523,000 new cases of work-related illness reported in this period, these two types of disorder accounted for 73% of cases (37% for stress, depression or anxiety, and 36% for MSDs). This reflects the incidence rate (the rate at which new cases occurred in the population during the time period rather than the prevalence rate (the proportion of the population who were cases at a point in time. ¹

Not only are stress and MSDs the two most common causes of work-related ill-health, but there is also growing interest in the links between the two conditions, both in terms of common risk factors and the extent to which the conditions themselves are mutually influential.

Psychosocial factors have been associated as a risk with both stress and MSDs. The term ‘psychosocial factors’ describes a host of potential influences on health, including those relating to the environment, the nature of work or work tasks, relationships and individual factors such as beliefs, attitudes or personality traits.

In the context of work-related stress, based on an extensive review of the literature,² the Health and Safety Executive’s Management Standards identify the following factors as most pertinent to the management of work-related stress:

• Demands – unrealistic or unachievable demands/workload, job design exceeding an individual’s capacity, poor task design or poor physical environment.
• Control – lack of employee discretion over the way in which tasks are carried out, lack of authority and few opportunities for the employee to use their skills or initiative.
• Support – lack of encouragement, sponsorship or resources provided by the organisation, line management and colleagues.
  Relationships – absence of effective procedures for avoiding conflict or unacceptable behaviour at work (eg, bullying, harassment).
• Role – conflicting or ambiguous roles.
• Change – poor management of change including implementation of new ways of working or new technology, lack of appropriate consultation with employees over change, and lack of appropriate support for employees during periods of change. It is also now generally accepted that risk factors for work-related MSDs include both physical and psychosocial factors. Psychosocial factors most commonly associated with MSDs are those relating to the work environment or work tasks, such as demands, repetitiveness, job control, job satisfaction, role clarity or social support at work.^3,4,5

For lower back pain (LBP), psychosocial factors are of a more individual nature. Pain beliefs (or ‘yellow flags’) have been identified as predictive of prolonged work disability and progression into chronicity.⁶ Workers’ own beliefs that their LBP was caused by their work, that their back pain is dangerous or potentially disabling, or that they are unable to return to work, are particularly important.

Due to the common risk factors associated with the onset of both MSDs and stress – depression or anxiety – it is perhaps unsurprising that an association has also been identified between the conditions themselves. For instance, high perceived job stress has been consistently associated with upper extremity problems.⁷ And a significantly higher proportion of individuals with major depressive disorder (MDD) have been found to report disabling chronic pain than those without MDD (41% of those with MDD versus 10% of those without MDD^).8

Most of this type of research, however, has been cross-sectional in nature (within a narrow time span), making it difficult to determine causation. The small number of prospective epidemiological studies that does exist provides support for a predictive relationship between symptoms of psychological strain and LBP.

For example, one piece of research has identified psychological distress as the only pre-existing influence on new episodes of LBP other than a history of LBP.⁹

The specific route or routes by which psychological stress/strain might influence MSDs is a matter of debate. A number of different paths have been proposed in the literature, reflecting both one-way and mutual causality. One proposition is that psychological stress/strain influences musculoskeletal discomfort through the physiological and biological systems, affecting internal tolerances.

For instance, psychological stress and or strain may induce physiological stress and muscle tension,¹⁰ which may result in adverse changes in immune system response, or even changes in adrenaline or noradrenaline.¹¹

Alternatively, it has been speculated that increased levels of psychological stress/strain may cause individuals to perform tasks differently (excessive keying force when typing, for instance), producing variation in biomechanical loading.³ A third possibility is that a poor psychosocial environment may increase symptom reporting, or variations in the experience of pain, impairment or disability, through different behavioural and cognitive responses.³

Views from practice

In addition to research evidence, the views and experience of OH advisers (OHAs) from practice provides important anecdotal evidence. In recognition of this, OH service provider Cope conducted a survey to capture the views and experiences of Cope OHAs with regard to stress, depression or anxiety and MSDs.

Fifteen OHAs completed the electronic survey, reflecting the combined provision of OH support and advice to more than 26,000 employees in a range of organisations and industrial sectors across the UK. The main questions were:

What proportion of the individuals that you see with musculoskeletal problems, do you believe are also suffering from stress, depression or anxiety? The largest proportion of respondents (40%) estimated ‘about half’.

Of those experiencing both types of problem, what proportion, in your opinion, developed the MSD first, and what proportion developed the stress, anxiety or depression first? The majority of respondents felt that the MSD was likely to have developed first, in most cases.

How often do you believe MSDs and stress, depression or anxiety are influenced by the same risk factors? The vast majority (93%) of OHAs said ‘very often’ or ‘often'.

This short survey provides an indication that the experiences of Cope’s OHAs in practice are consistent with the findings emerging from research on the issue of stress and MSDs. Namely, that co-existence of stress and MSDs could be a significant issue for rehabilitation following both stress and MSDs, with co-existence of the two conditions potentially acting as a barrier to recovery. Indeed, co-existence of stress, depression or anxiety and MSDs has been found to magnify the negative impacts of the single conditions on individuals’ labour force activity.¹²

Thus, there may be scope for improving interventions aimed at tackling stress and MSDs by addressing the commonalities or interactions between the two problems. Interventions aimed at tackling the risk factors common to both conditions might be more effective in improving the health of individuals, and as a result, that of organisations through increased productivity and reduced sickness absence rates.

Both physical and psychological strain can be seen as resulting from an imbalance between individual capacity and the demands of the environment. As reflected in Figure 4 (see left), excessive physical demands can overload the musculoskeletal system, resulting in tissue breakdown and leading to physical symptoms such as neck, shoulder or back pain.

Lack of use, or ‘underloading’ can also prove detrimental as tissues become weakened, are not strong enough to cope with demands, and are therefore susceptible to failure. Similarly, when psychological demands exceed an individual’s coping capacity, psychological stress/strain is likely to result.

Underloading can also affect an individual’s psychological wellbeing as boredom or monotony can be considered a source of stress for some individuals. Of course, the point at which optimal loading is reached will vary from individual to individual according to many factors, including physical and mental fitness or resilience.

It is the role of OH practitioners, including ergonomists, occupational psychologists and physiotherapists, to help employers design work tasks, equipment and environment in such a way that avoids under or overloading, and to enhance employees’ capacity to maintain this balance.

Conclusion

Due to the complexity and interactive nature of the two types of condition, effective management of both stress and MSDs requires a comprehensive, multidisciplinary approach, incorporating concepts from physiotherapy, ergonomics and psychology.

Yet despite the growing body of evidence for commonalities between stress and MSDs, many approaches to the prevention and management of these conditions tend to derive from these individual disciplines in isolation from the others.¹³

Adopting a more holistic approach, taking into account the commonalities and interactions between stress and MSDs, may well achieve much needed reductions in these two highly prevalent conditions.

Zara Whysall is senior research scientist and occupational psychologist at Cope OH Services

References

1. Health and Safety Executive (2007) Self-reported work-related illness and workplace injuries in 2005/06.
   Health and Safety Executive Books: Sudbury, UK
2. Rick J, Thomson L, Briner RB, O’Regan S, Daniels K (2002) Review of existing supporting scientific knowledge to underpin standards of good practice for key work-related stressors-Phase I. Contract Research Report 427/2002, Health and Safety Executive Books, Sudbury, UK
3. National Research Council and Institute of Medicine (2001) Musculoskeletal disorders and the workplace: Low back and upper extremities. National Academy Press, Washington DC
4. NIOSH (1997) Musculoskeletal disorders and workplace factors: A critical review of epidemiologic evidence for work-related musculoskeletal disorders of the neck, upper extremity, and low back. DHHS (NIOSH) Publication No. 97-141, Cincinnati
5. Devereux J, Rydstedt L, Kelly V, Weston P, Buckle P (2004) The role of work stress and psychological factors in the development of musculoskeletal disorders, Health and Safety Executive Research Report 273. Health and Safety Executive Books, Sudbury, UK
6. Waddell G, Burton K (2000) Occupational Health Guidelines for the Management of Low Back Pain at Work – Evidence Review. London: Faculty of Occupational Medicine
7. Bongers EMF, van Bokhoven H, van Thienen MN, Kooyman MAP, van Beersum SEC, Boetes C, Knoers NVAM, Hamel BCJ (2002) Are psychosocial factors risk factors for symptoms and signs of the shoulder, elbow or hand/wrist? A review of the epidemiological literature. American Journal of Industrial Medicine, 41: 315-342
8. Arnow B, Hunkeler E, Blasey C, Lee J, Constantino MJ, et al. (2006) Comorbid Depression, Chronic Pain, and Disability in Primary Care. Psychosomatic Medicine, 68: 262-268
9. Feyer AM, Herbison P, Williamson AM, de Silva I, Mandryk J, Hendrie L, Hely MC (2000) The role of physical and psychological factors in occupational low back pain: a prospective cohort study. Occupational and Environmental Medicine, 57: 116-20
10. Lundberg, U (2002) Psychophysiology of Work: Stress, gender, endocrine response, and work-related upper extremity disorders. American Journal of Industrial Medicine Supplement 2: 383-392
11. Theorell T, Karasek RA (1996) Current issues relating to psychosocial job strain and cardiovascular disease research.
    Journal of Occupational Health and Psychology 1: 9-26
12. Waghorn CD, Lloyd C (2006) Labour force activity among Australians with musculoskeletal disorders comorbid with depression and anxiety disorders. Journal of Occupational Rehabilitation, 16: 235-246
13. Marras WS (2004) State of the art research perspectives on musculoskeletal disorder causation and control: the need for an integrated understanding of risk. Journal of Electromyography and Kinesiology,14: 1-5