The diagnosis of ME/CFS is sometimes complicated by co-existing conditions such as fibromyalgia, multiple chemical sensitivity, irritable bowel syndrome, migraines, allergies and depression. They may develop 'in the setting of ME/CFS' (e.g. multiple chemical sensitivity) or pre-date it but then 'become associated with it'.

Fibromyalgia

ME/CFS and fibromyalgia are often closely connected and it is suggested they should be considered as overlapping conditions.

There are key differences between ME/CFS and fibromyalgia: ME/CFS is commonly initiated by a viral infection and fibromyalgia by physical trauma. In fibromyalgia pain is the major symptom - in ME/CFS it is fatigue and post-exertional malaise. Aerobic exercise will exacerbate symptoms in people with ME/CFS whereas people with mild fibromyalgia may be able to tolerate it better.

The disability experienced by people with ME/CFS is often aggravated when fibromyalgia and chemical sensitivity are also present.

More information:

Fibromyalgia: Clinical Working Case Definition, Diagnostic and Treatment Guidelines A Consensus Document

Fibromyalgia: A Clinical Case Definition and Guidelines for Medical Practitioners, An Overview of the Canadian Consensus Document

Busch AJ et al., (2008) 'Exercise for Fibromyalgia: A Systematic Review' Journal of Rheumatology, vol. 35, no. 6, pp. 1130-1144.

Depression

Research has provided clear evidence that ME/CFS is not the same as depression or any other psychiatric disorder and no antidepressant has been shown to improve the core symptoms of ME/CFS. (4)

Depression can co-exist with ME/CFS but the incidence of depression with CFS is no higher than in people with other chronic illnesses. (5) There have been cases where people with ME/CFS have been wrongly diagnosed with major depression leading to inappropriate treatment.

The essential characteristics for a diagnosis of depression are a persistent, low or irritable mood and loss of pleasure and guilt or self blame whereas the essential symptoms of ME/CFS are severe, prolonged fatigue, post-exertional malaise, sleep dysfunction, pain, neurological/cognitive, autonomic, neuroendocrine and immune manifestations. (4)

Some of the clinical differences between depression and ME/CFS are tabulated below:

Differentiating ME/CFS and depression: Clinical presentation

Adapted from Stein E, (2005) 'Assessment and Treatment of Patients with ME/CFS: Clinical Guidelines for Psychiatrists'.

There are also physiological differences between ME/CFS and depression, including raised urinary cortisol excretion with depression.

A sub-set of people with ME/CFS develop reactive, situational depression secondary to the loss of their health and previous lifestyle. 'It is important to discern whether the patient has ME/CFS, a psychiatric condition or both. Using the Canadian Criteria, the signs and symptoms of ME/CFS can clearly be distinguished from psychiatric disorders in most cases' (Stein 205, p.19).

Dr Eleanor Stein (Psychiatrist and ME/CFS practitioner) summarises the evidence that ME/CFS is not a psychiatric or psychological disorder and addresses various issues concerning ME/CFS (such as anxiety and grief) from the psychiatrist's perspective in 'Assessment and Treatment of Patients with ME/CFS: Clinical Guidelines for Psychiatrists' (2005).

More information:

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Clinical Working Case Definition, Diagnostic and Treatment Guidelines A Consensus Document

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Clinical Case Definition and Guidelines for Medical Practitioners, An Overview of the Canadian Consensus Document