Dear Editor,

Many thanks for Dr Chan Kwok Wai's comments. I shall list my answer point by point as follows:

1. I agree that the relationship between psychogenic pain and the noxious stimulus is less well defined. All patients with chronic pain may in fact develop some psychological reactions and problems sooner or later.
   
   
2. I agree with the meaning of nociception as specified.
   
   
3. While the International Association of the Study of Pain (ISAP) does try to expand the definition of pain, this is probably more academic than practical. "Pain" is such a complicated symptom of human being that many aspects are still poorly understood. The interplay between psychogenic and organic pain makes our study in humans very difficult. This is particularly important when one carries out drug trials in pain relief as it is often difficult to establish an universally accepted golden criteria for measuring the effect of the drugs, and individual variation of the patient's "Psychic" state often affects the results of any such drug trials.

K F Chin, MBBS(HK), FRACP, FHKCP, FHKAM(Neurology) Neurologist in Private Practice.