Here are some interesting excepts from a
Harvard study on the use of Peyote.
After five years of research, Halpern and other McLean researchers did not find any evidence of brain damage or psychological problems in church members who frequently use peyote, which contains the hallucinogen mescaline.
In fact, they found that members of the Native American Church performed better on some of the neuropsychological tests than other Navajos who do not regularly use peyote.
Test results for 61 church members who have used peyote at least 100 times were compared against those for 79 Navajos who do not regularly use peyote and 36 tribe members with a history of alcohol abuse but minimal peyote use. Those who had abused alcohol fared worse on the tests than the church members, according to the study.