The question of the prevalence of Psychophysiologic Disorders (PPD) is an important one so I looked into it a little more. The original study of this issue was by Kroenke & Mangelsdorf in 1989 and found that 70% of primary care patients had no explanation for their symptoms 12 months after they first went to their primary care physician. However, this study was done on a military base and though it included non-military family may not have been representative of the general public.
