Conditions comorbid with chronic fatigue in a population-based sample

Chronic fatigue syndrome (CFS) has been found to be comorbid with various medical conditions in clinical samples, but little research has investigated CFS comorbidity in population-based samples.

This study investigated conditions concurrent with a CFS-like illness among twins in the population-based Mid-Atlantic Twin Registry (MATR), including chronic widespread pain (CWP), irritable bowel syndrome (IBS), and major depressive disorder (MDD).

A survey was mailed to participants in the MATR in 1999. Generalized estimating equations were used to estimate odds ratios to assess associations between CFS-like illness and each comorbid condition.

A total of 4590 completed surveys were collected. Most participants were female (86.3%); mean age was 44.7 years. Among participants with a CFS-like illness, lifetime prevalences of CWP, IBS, and MDD were 41%, 16%, and 57% respectively. Participants reporting at least one of the three comorbid conditions were about 14 times more likely to have CFS-like illness than those without CWP, IBS, or MDD (95% confidence interval 8.1%-21.3%). Only MDD showed a temporal pattern of presentation during the same year as diagnosis of CFS-like illness. Age, gender, body mass index, age at illness onset, exercise level, self-reported health status, fatigue symptoms, and personality measures did not differ between those reporting CFS-like illness with and without comorbidity.

These results support findings in clinically based samples that CFS-like illness is frequently cormorbid with CWP, IBS, and/or MDD. We found no evidence that CFS-like illnesses with comorbidities are clinically distinct from those without comorbidities.