Approximate 4 million U.S. adults suffer from chronic fatigue syndrome (CFS) . Afflicted individuals endure chronic, incapacitating physical and mental fatigue that is not relieved by rest. Fatigue is exacerbated by physical or mental exertion and is accompanied by impaired memory and concentration, unrefreshing sleep, muscle and joint pain, and other defining symptoms [2–4]. The pathophysiology of CFS remains inchoate; there are no diagnostic clinical signs or laboratory markers.
CFS patients, their families, employers and society bear significant costs associated with the illness. The symptoms characterizing CFS are common to many illnesses. Hence, diagnosis is complex and requires exclusion of medical and psychiatric conditions that present similarly and requiring extensive diagnostic testing and clinical assessment [2–5].
There is no known cure. CFS management aims to relieve symptoms. Treatment is long-term and its associated costs can stretch for years or a lifetime. Patients, frustrated with lack of acceptable recovery often consult several providers and self-medicate their illness [6–9].
Finally, CFS can limit patients' ability to work and participate in other life activities. Illness frequently leads to withdrawal from the labor force, absenteeism or presenteeism. As patients earnings fall, burdens on employers and family members rise as afflicted individuals cease to engage in the home and the workplace [7–9].
International studies have documented the economic costs of CFS. An Australian study examined the healthcare utilization cost and the indirect costs incurred through cessation or reduction in employment during 1988 . The total annual healthcare cost for one CFS patient in Australia amounts to approximately $A2,000, of which $A1,268 was directed to the government. The mean income forgone by CFS patients in Australia was $A7,500 per year, of which $A1,700 was in tax revenue loss for the government. Overall, the economic impact of CFS to the Australian government and the community is approximately $A9,500 per patient. A Canadian study examined direct health care costs associated with fibromyalgia (FM) within a representative community sample . The annual direct medical cost in 1994 for FM to affected individuals was approximately $C2,275. McCrone et al assessed the economic cost of chronic fatigue and chronic fatigue syndrome in UK primary care between January 1999 and June 2001 . The mean total cost of services and lost employment across the sample was £1906 for the 3-month period with formal services accounting for 9.3% of this figure. Over 90% of the cost was accounted for by care provided by friends and family members and by lost employment. Patients with dependants had significantly higher costs than those with none and costs were also significantly higher for greater levels of functional impairment.
Two published studies have estimated the economic burden of CFS in the U.S [11, 12]. The first  was based on the 1997/1998 baseline data from a longitudinal population-based study on CFS between 1997 and 2003 in Wichita, Kansas. Data were collected by telephone interview from a sample that included 43 persons with CFS, 3,485 suffering fatiguing illness that was not CFS, and 3,634 non-fatigued controls. Persons with CFS had 37% lower household productivity and 54% lower labor force productivity than comparable controls, resulting in annual productivity losses of between $12,000 and $28,000. A second study  focused on the direct medical costs associated with CFS. Utilizing archival health utilization data from an epidemiological study of CFS in Chicago, Illinois conducted between 1995 and 1998, the study computed incremental healthcare costs for 21 persons with CFS as compared to 15 healthy controls. The authors estimated that persons with CFS spent $2,342 more annually on direct medical costs than healthy individuals did.
The current study extends the prior work in four important dimensions. First, the study employs validated standardized criteria  that are presently recommended , including medical and psychiatric evaluations, to diagnose CFS. Second, it draws on a larger sample of CFS and non-fatigued individuals than available in prior work, permitting a richer and more precise analysis of healthcare and employment costs related to CFS. Third, the study uncovers an important pathway to the "productivity costs" related to CFS. CFS can forestall educational attainment, and hence illness places afflicted individuals on a lower trajectory of lifetime earnings. Finally, the study is more comprehensive than prior work, directly collecting data from patients on detailed direct medical expenditures, employment and earnings. This permits us to examine healthcare use and employment effects from the same sample, and track their relationship.