The epidemiology of chronic fatigue, physical illness, and symptoms of common mental disorders: a cross-sectional survey from the second British National Survey of Psychiatric Morbidity.

OBJECTIVE: The study aimed to describe the prevalence of chronic fatigue in the general population and to investigate the extent to which its association with physical illness was independent of other symptoms of common mental disorders.
METHODS: Data from the second British National Survey of Psychiatric Morbidity (2000) were analyzed. The survey covered people aged 16 to 74 years living in private households. Chronic fatigue (significant reported fatigue lasting 6 months or more) was ascertained using the revised Clinical Interview Schedule. Information on reported physical illness and sociodemographic factors was considered. Psychiatric symptoms were also assessed using the revised Clinical Interview Schedule.
RESULTS: The prevalence of chronic fatigue was 15.0%, and this showed a significant association with the number of reported physical illnesses (odds ratio [OR] per reported illness, 1.79; 95% confidence interval, 1.68-1.90). It was higher in midlife, in women, in participants with less skilled occupations, and in those with lower educational attainment. Chronic fatigue was strongly associated with the presence of depressive symptoms (OR, 5.37), anxiety-related symptoms (OR, 4.66), and with sleep complaints (OR, 4.41). After adjustment for all sociodemographic and psychiatric factors, the number of reported physical illnesses was less strongly but still significantly associated with chronic fatigue (OR, 1.51; 1.39-1.63).
CONCLUSION: Physical illness is strongly associated with chronic fatigue. Symptoms of common mental disorders are also associated with chronic fatigue, but the association between physical illness and chronic fatigue is evident even after adjusting for psychiatric symptoms. The assessment of physically ill people should include chronic fatigue and psychiatric symptoms.