Robert Bergman, MD, in "Navajo Peyote Use: Its Apparent Safety," _Amer.
J. Psychit. 128(6):51-55/695-699, writes: 

"Some rough estimates of the rate of negative reactions to peyote can be
made.  The Native American Church of Navajoland estimates its membership
at 40,000.  This estimate may be high and there may be inactive members,
so we will use a population base of 30,000.  Our informants report attending
meetings with an average frequency of about twice a month.  Since this may
be exaggerated, we will assume an average attendance of only once every
two months.  This would result in a total of 180,000 ingestions of peyote
per year by the population we serve.  Assuming that all five of our cases
represent true reactions to peyote and that we hear about only half of
the cases occurring, the resulting (probably overestimated) rate would
be approximately one bad reaction per 70,000 ingestions."

"This rate is much lower than others that have been reported for the use of
hallucinogenic agents, and it calls for at least some attempted explanation.
It is thought that the usually repressed emotions freed by hallucinogens
sometimes are not integrated and cause panic or psychosis.  I believe that
the feelings made available at meetings are carefully channeled into
ego-strengthening directions.  Some of the crucial factors are a positive
expectation held by the Peyotists, an emphasis on the real interpersonal
world rather than the world within the individuals, emphasis on communion
rather than withdrawal during the drug experience, emphasis on adherence
to the standards of society rather than the freeing of impulses, and certain
practices during the meetings."

---

As you can see from this estimate, the incidence of negative reactions
among peyote users is very low when the substance is taken in controlled
circumstances.  We should note that there may be a sampling bias in the
quoted estimate since people who experience repeated or severe problems
after using psychedelics may drop out of the Church.  

The 5 case reports which the article mentions involve: one man who, against
rules, had been drinking and experienced a paranoid panic attack after
taking peyote and who recovered in 24 hrs but quit attending the
ceremonies; an acute schizophrenic episode which began at the time of
the meeting and became worse over the next few days but improved after
inpatient treatment and didn't prevent attendance at further meetings;
a man who had attended ceremonies at the insistence of his wife and
over the objections of his family and who reported feelings of anxiety
and depersonalization which stopped after he quit attending meetings and
worked out some of his feelings about the marriage; and two chronic
schizophrenic patients who became anxious during meetings but who continued
to attend them without untoward effects.

This is too small a sample of cases to say anything meaningful, but it
is important to note that diagnosed schizophrenics are able to comfortably
ingest peyote.  This strongly suggests that mescaline and psychedelics do
not cause psychotic episodes directly but at best trigger episodes through
some stress-related mechanism.  After all, if psychedelics directly inter-
acted in a negative manner with whatever neurosystems go awry in psychosis 
and schizophrenia, then we would expect them to increase the symptoms of 
these disorders.  This conclusion is in keeping with that of Rick Strassman's
literature survey on the subject (which I have repeatedly quoted on the
net and can e-mail copies of those postings to interested parties).

     --Matt, bagg@midway.uchicago.edu

==========================================================================

However, I must disagree with the claim that mescaline isn't as well studied
as LSD.  It is true that LSD has been studied more in the recent past,
but this research has usually only used it as a pharmacological
tool.  Back when studies were being done on LSD's effects on health,
parallel research was being done on mescaline.  The fact that mescaline
had a higher effective dose compared to LSD actually proved helpful
since it made it easier to do studies on mescaline's disposition in vivo.
The metabolic pathways of mescaline have been pretty exhaustatively
characterized.

Furthermore, mescaline, unlike LSD, had a long tradition of use (1600 years
among the Huichol Indians) which allowed long-term studies to be easily
done.  For example, Oscar Janiger and some others published a study on
the effect of peyote on human chromosomes (Dorrance, Janiger, and Teplitz
(1975), _JAMA_ 234:299-302) among the Huichols and found no abnormalities.
They estimated that the people they tested took peyote up to 35 times
a year and had been doing so for essentially all of their lives.
Another study, among the Yanomama Indians of Venezuela (Bloom et al
(1970) _Proc Natl Acad Sci USA_ 66:920-927), found no difference in
chromosomal damage between males and females despite the fact that only
males ingested peyote.

Admittedly, I can think of no studies which evaluate how carcinogenic
mescaline is, for example.  But on the other hand, have such studies been 
carried out with respect to LSD?  I really do think that mescaline is as 
well characterized as LSD.  Every time he writes something about mescaline, 
Sasha Shulgin likes to introduce it as one of the most thoroughly studied
drugs WRT metabolism and biochemistry.  We might worry about subtle
effects on health, especially given the fact that the effective dose is
a pretty significant one, but for now these worries are unfounded.

You are correct that the duration isn't particularly different.  I was
estimating from limited personal experience, but the various authorities
don't seem to support that idea.  It seemed to me that there initial phase 
'cut into' the psychedelic phase, but, again, I don't have any real evidence 
to support that.  I haven't noticed a significant difference in onset.

>Jeremy

    --Matt