Though numerous questions remain unanswered, conditions like coronary heart disease & cancer are usually identifiable & several of the processes involved are known. Less is known about what is going on in many other diseases. These pose Diagnostic Dilemmas. Whether a condition is purely medical often can't be determined in a yes-or-no fashion. There are grey areas, stemming from lack of medical knowledge, the way in which patients describe their problem & doctor's skill at eliciting patient info from their patients. Also the assumption that mind & body are separate, illness needs to be categorized as either physical or mental.
An example of Diagnostic Dilemma is Chronic Fatigue Syndrome, a clinical condition in which the patient complains of extreme tiredness accompanied by poor concentration, irritability & muscle pain. Many family physicians believe that the symptoms of most patients suffering from chronic severe fatigue are not readily explained, either by recognized organic disease or by depression, anxiety, anger or some other emotional reaction.
A clinical syndrome in which the complaint of fatigue is severe & accompanied by symptoms similar to those described earlier has been recognized at least since nineteenth century. In late 1800s, this syndrome received diagnosis of Neurasthenia, a condition of uncertain cause but attributed to the effect of the stresses of modern life on the human nervous system. Although there is disagreement about the defination of CFS, at present time it can be characterized by present of certain symptoms(inclusion criteria) & absence of others(exclusion criteria).
More research is needed to determine the nature & cause of CFS, so far, no single definitive cause of the disorder has been identified. What is now known, however, suggest that a viral infection seems to be a frequent participating agent. The studies, carried out generally lack comparison groups & detailed information about patient studied, or have other important limitations. One interesting finding is that, while CFS patients often report having difficulty in concentration & memory, their actual cognitive performance is normal( Werden & Appleby, 1997). Immunological abnormalities are common in CFS, as are abnormalities of autonomic functioning & feelings of depression & anxiety.