I believe WT is off base in calling the altitude effect merely mental. As a Physician, Flight Surgeon and Sports Medicine specialist and also having served as the Chief Physician for the Honolulu International Airport for 31/2 years I have had occasion throughout my career to deal with many altitude sickness problems. It is not merely"mental' but has a definite physiologic effect on the body, primarily on the Red Blood Cells in the body. I have encountered problems with Cyclers. Mountain Climbers , Novice Hikers and of course Air Force Pilots.