It would be interesting to see data showing how often some symptoms are "all in their head." If certain symptoms are commonly presented by people who are drug seeking or have bonafide psychological problems, it creates a large amount of noise in which doctors need to find a signal.

I suspect, useless as my suspicions can be, that HOW symptoms are presented play an important role in how seriously a doctor takes their patients. Someone whose symptom descriptions change with each visit, whose symptoms are contradictory, or even patients who feel the need to describe every minuscule detail of their lives in hopes that anything helps provide a diagnosis can give the impression that the patient is not experiencing a treatable medical condition. Long-term histories with patients can taint a physicians outlook when James comes in one week because of an "itchy nose," and the next demanding prescriptions for his mild cold symptoms, etc. It can be hard to take him seriously when he presents with vague symptoms of what could be more serious.