to the editor: I read with interest “Chronic Fatigue Syndrome: Evaluation and Treatment,” in American Family Physician.¹ As with most reviews of chronic fatigue syndrome (CFS), Drs. Craig and Kakumanu go into great detail proposing the etiologic links with infectious, neuroendocrine, and immunologic causes. Regrettably, their article glosses over the possibility that the key etiologic factor in CFS could actually be depression. To state that “CFS…is often dismissed by physicians as … a manifestation of clinical depression”¹ downplays the significance of depression as a disease entity. Since when is making a diagnosis of depression, which is a common illness of patients in family practice offices, a “dismissive” act?

Despite noting that two thirds of patients with CFS have signs of major depressive illness, the authors attempt to distance CFS from depression by noting that “patients with CFS also show symptoms that are not typical of clinical depression, such as sore throat, lymph-adenopathy, and postexertional malaise.”¹ While this may be true, it should also be noted that these symptoms, including lymphade-nopathy, are often self-reported in patients with CFS, just as back pain, headache, and other somatic symptoms are often self-reported in patients with depression. In addition, the fact that “patients with CFS lack feelings of anhedo-nia, guilt, and decreased motivation,” certainly does not mean that they are not depressed. Many patients who are clinically depressed do not exhibit these symptoms, either.

Unfortunately, it seems that many researchers of CFS are going out of their way to distance themselves from the possibility that CFS might be an atypical manifestation of clinical depression. Why is this, when clinical depression has been recognized as a biologic entity for years? Family physicians have been at the forefront of educating the public about this fact. Yet, for some reason, many researchers seem to think that linking the etiology of CFS to clinical depression somehow makes CFS less of a “disease.”

As the authors note, “the diagnostic ambiguity surrounding CFS invariably leads to imprecise and inconsistent epidemiologic statistics.” Despite millions of dollars of research, even the incidence of CFS is unknown. Could CFS be less of a “neuroendocrine-immunologic” process, and more of a somatized, atypical presentation of clinical depression? In my opinion, this question has never been adequately addressed.

Unfortunately, for many patients, the notion that CFS must be something more than “just” depression effectively demotes the diagnosis of clinical depression to a less-than-clinical entity. If CFS, in all of its manifestations, is found to be caused by depression, does that make it less of a true disease? Of course not.

There needs to be continued research into CFS. The dimensions and incidence of this illness must be better defined as we sift through the relative “zebras” of neuroendocrine, allergic, and immunologic potential sources.

At the same time, to continue to largely ignore the “elephant” of depression that is standing in our midst is both wasteful and ill-advised.

in reply: I read Dr. Frey's letter with great interest. I agree that depression is a frequent and often overlooked disease. Patients with depression often present with somatic complaints such as fatigue. It was not the intent of our article¹ to discuss at length the role depression plays in chronic fatigue syndrome (CFS), but instead to develop and discuss CFS as a unique syndrome which, despite being heterogenous, does appear to exist. By definition, if depression is the cause of the patient's somatic complaints, the patient does not have CFS. It is only after other etiologies are eliminated and it is decided that the cause of the patient's symptoms is or appears to be idiopathic that the diagnosis of CFS can be made.

I also agree with Dr. Frey that depression is a frequent coexisting disease with CFS; however, it is often reactive, being secondary to patients' inability to maintain their previous lifestyle. In fact, the depression experienced in patients with CFS can often be differentiated by their desire to get better, whereas patients with primary depression often do not care to improve. Nonetheless, psychiatric care has proven to be a successful intervention in patients with CFS. Psychiatric care is properly indicated in most of our patients who were once functioning ideally and, for whatever reason, suddenly became incapacitated by an illness that left them dependent and poorly productive despite their earnest attempts to improve themselves.