Both musculoskeletal conditions and mental illness are common in Australia's working age population. This factsheet, based on "Bulletin 80" from the Australian Institute of Health and Welfare," provides an introduction to both groups of disorders, and outlines the numbers of Australians aged 16-85 who suffer from each. It also provides information about "comorbidity," i.e. the simultaneous occurrence of musculoskeletal conditions and mental health difficulties.

Chance is one possible explanation for the simultaneous occurrence of different health conditions. However, according to the Australian Institute for Health and Welfare, health conditions often occur together because of "direct or indirect causal relationships between them."

It is likely that there is a causal relationship between musculoskeletal and mental health conditions. Which leads us to the age-old question: which comes first, the chicken or the egg? And regardless of which came first, how are comorh5bid mental health and musculoskeletal disorders best managed and treated?

Musculoskeletal conditions 

At any point in time, more than 6.1 million Australians aged 16–85 years have a musculoskeletal condition (38% of that population).  

There are more than 200 kinds of musculoskeletal conditions, with a variety of potential causes including:

• The overuse of joints;
• Musculoskeletal anomalies that have been present from birth;
• Infections;
• Inflammations;
• Trauma / injury;
• Cancer; and
• Metabolic or biochemical abnormalities.

Common musculoskeletal conditions include:

• Arthritis;
• Osteoarthritis;
• Rheumatoid arthritis;
• Gout;
• Back and neck pain; and
• Osteoporosis.

Symptoms typically associated with musculoskeletal injuries include:

• Pain, which may be:
  • Acute, i.e. short and sharp; or
  • Chronic, which may last weeks, months or years;
• Stiffness;
• Physical limitation; and
• Other poor health outcomes.

The older someone is, the more likely they are to have a musculoskeletal condition. Women are more likely than men to suffer from musculoskeletal problems.

Mental illness

In a 12-month period, 3.2 million (20%) of Australians in the 16-85 age bracket will experience a mental disorder.

The most common types of mental disorders in Australia are:

• Anxiety disorders, including:
  • Panic disorders;
  • Phobias;
  • Obsessive-compulsive disorder; and
  • Post-traumatic stress disorder;
• Depression; and
• Substance-use disorders.

Mental disorders often begin in childhood, adolescence or early adulthood (18-29 years). The proportion of men and women suffering from mental disorders decreases with age.

Anxiety and depression are more common in women. Substance-use disorders are more common in men.

When mental illness and musculoskeletal conditions meet…

Over 1.5 million people (10% of Australians aged 16–85 years) had at least one musculoskeletal condition and one mental disorder over the last 12 months.

Of this group, more women (862,000) than men (671,000) experience mental illness and a musculoskeletal condition simultaneously.

Rates were also affected by age-group:

• 16-24 years: 6% comorbidity;
• 25-34 years: 8% comorbidity;
• 35-44 years: 12% comorbidity;
• 45-54 years: 15% comorbidity;
• 55-64 years: 9% comorbidity;
• 65-74 years: 6% comorbidity; and
• 75-85 years: 5% comorbidity.

It has been estimated that by 2016, more than 80% of Australian workforce growth will come in the 45+ demographic. Since 45-54 years is the demographic most likely to suffer from simultaneous mental health and musculoskeletal conditions, this issue looks set to become increasingly significant in the workplace.
    
Chance may play a role in comorbidity, however the Australian Institute for Health and Welfare calculated that there were 470,000 more Australians who had both a musculoskeletal condition and a mental disorder "than would be expected if occurrences of the two conditions were independent of one another".    
    
In 2007, 25% of people with a musculoskeletal condition also had a mental disorder, while 48% of people with a mental disorder also had a musculoskeletal condition.  

In both instances, the numbers of people experiencing comorbidity were highest in the 45-54 age group, and lowest in the 75-84 age group.

People with back and neck problems were more likely than people with arthritis, rheumatism or gout to also suffer from mental disorders. The most common mental disorder experienced by people with a musculoskeletal condition was anxiety.

The chicken AND the egg

It is likely that, in some instances, musculoskeletal conditions cause mental disorders, via:

• Stress caused by physical limitations;
• Irritability, insomnia and exhaustion that may result from chronic pain;
• Withdrawal from work and social activities; and
• Feelings of helplessness.

It is also likely that mental disorders sometimes cause musculoskeletal conditions, via:

• Changes to the immune, endocrine and nervous systems; and
• Behavioural risk factors such as:
  • Poor diet;
  • Lack of physical activity; and
  • Substance use.

 
According to the Australian Institute of Welfare and Health, "Published studies suggest that causal pathways are more likely to be from musculoskeletal conditions to mental    disorders than    the reverse, although the latter can also occur."

The way forward for health and allied professionals

• Be aware that there is clear association between musculoskeletal conditions and mental disorders.
• Adopt a multidisciplinary approach when managing people suffering from musculoskeletal and mental health disorders simultaneously.
• Be prepared for complications to treatment and management plans for people suffering from both types of disorders. For example, interactions between medications, or limitations on exercise.
• Expect clinical management--and the management of these issues in the workplace--to be more complex and time-consuming, and allocate time and resources accordingly.