Hi all,

 It turns out the body has a natural mechanism for dealing with pain and uses serotonin as a part of that process.  Well, turns out also, that todays most common painkillers like Tylenol(TM) etc., the group of NSAID analgesics, deplete your levels of serotonin making it harder for you to deal with pain levels by yourself and relying on further doses of Tylenol etc.

 (The NY Times carried a story of a women  who found herself needing to take more and more Tylenol to keep the pain at bay and wrote an in-depth article on the effects of serotonin, etc)

 -Peter