Common mental disorders such as depression are the most frequent cause of long-term sickness absence. These absences tend to last longer and account for a disproportionate part of employers’ costs.
Although they have been overtaken by common mental disorders, physical conditions such as musculoskeletal disorders still account for a substantial proportion of long-term sick leave.
But employees cannot be divided neatly into those with physical health problems and those with mental health problems. Physical and mental health conditions frequently co-occur. About 45% of people with mental disorders also have a physical health problem, and 30% of patients with a long-term physical condition also have a psychiatric disorder. Almost five million people in the UK have both.
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The relationship between physical and mental disorders is complex; each can cause the other. Moreover, people with co-morbid conditions have worse outcomes. For example, depressed patients are more likely to die after a heart attack or have diabetic complications.
The precise reasons for these differences are not clear, but health behaviours such as drinking, smoking, diet and exercise, and treatment adherence, are part of the explanation.
Research has found that sickness absence is greater in those with both physical and mental disorders. But this additional sick leave is more than would be expected from just adding the two conditions together.
This is potentially of great importance to those tasked with managing employees on sickness absence. Many employees will be aware that they have both a physical and a mental health condition. Those managing them need to consider the contribution of each, as well as the combination, when formulating a return-to-work plan.
An important factor to recognise is that the physical health condition may be slower to respond to treatment than the mental health condition.
But employers are not always aware that there is an additional mental health problem complicating an employee’s sick leave. Even if the employee’s doctor knows about it, they may not communicate it on a fit note.
The fit note, in contrast to the old FMED3, allows for more than one condition to be declared, although this is done relatively rarely. The perceived stigma of psychiatric disorders means the patient will often ask the doctor to declare only their physical diagnosis.
It is also possible that the mental health condition will get missed. Many of the symptoms of depression occur as part of a long-term physical health problem, or as a side-effect of treatment. Patients often feel such symptoms are to be expected and they do not complain. Doctors with little time and often no training in psychiatry may not probe too deeply.
The longer an employee’s sickness absence lasts, the more likely it is that there is a psychological component. The common mental disorder may have been there all along, or may be brought on by the loss of structure and increased social isolation that accompany sickness absence.
The problem will be recognised only if someone considers it. The possibility of there being an additional mental disorder should be considered for all employees on long-term sick leave, even if their fit note is for a physical disorder.
Such an employee might be encouraged to alert their doctor to symptoms of low mood, poor sleep or increased irritability. Occupational health practitioners, where available, are increasingly skilled at recognising the contribution of common mental disorders to long-term sick leave. Occupational psychiatrists can assist with more complex cases.
The good news is that, if recognised, co-occurring physical and mental disorders are treatable. Sometimes specialist psychiatric input can help to select appropriate antidepressant medication for people already taking drugs for their physical health problem.
Cognitive behavioural therapy can help employees deal with the symptoms of their physical disorder, such as pain, as well as their mental health.
Sensitively involving occupational health, occupational psychiatry or a doctor could make the difference between an employee returning to work or having to leave their job.
Doctor Max Henderson is a consultant liaison psychiatrist at King’s College, University of London