Symptoms: in the Head or in the Brain?

Symptoms are a regular part of the human experience. A survey of more than 1 million persons found that 40% to 55% were experiencing headaches, 33% to 46% fatigue, and 15% sore throat at the moment they were being surveyed (1). Typically, the participants described these symptoms as being of only “slight” severity.

Sometimes a patient perceives a symptom as bothersome enough to constitute an “illness.” Dingle prospectively followed 443 persons for 10 years, for a total of 970 036 person-days. There were 9.4 instances per person-year in which the participants reported symptoms that caused impairment sufficiently severe to be described as illnesses. For only a minority of the “illnesses,” however, did the participants seek medical care (2). Thus, it appears that most people do not regard most symptoms as being illnesses or most illnesses as warranting a physician visit.

Nevertheless, much of our professional life is spent dealing with symptoms. Most visits to a physician are prompted by symptoms. According to the National Ambulatory Medical Care Survey, conducted by the National Center for Health Statistics, in 1998 there were 61.3 million office visits for symptoms of acute respiratory tract infection alone; in contrast, there were 61.0 million visits for the three most common chronic diseases—hypertension, diabetes mellitus, and chronic ischemic heart disease—combined (3).

The symptoms of “minor” illnesses lead to huge expenditures, even when people do not visit a physician. The multi–billion-dollar market in over-the-counter drugs is largely …