This correlational study (n=176) investigated the long-term residual psychological and cognitive effects of peyote use amongst native American Church members, compared between regular users (n=61), minimal users (n=79), and members with a history of alcohol dependence (n=36). Only members with prior alcohol dependence showed neuropsychological deficits, but there was no link between psychological or cognitive deficits linked to peyote use.

Abstract

“Background: Hallucinogens are widely used, both by drug abusers and by peoples of traditional cultures who ingest these substances for religious or healing purposes. However, the long-term residual psychological and cognitive effects of hallucinogens remain poorly understood.

Methods: We recruited three groups of Navajo Native Americans, age 18–45: 1) 61 Native American Church members who regularly ingested peyote, a hallucinogen-containing cactus; 2) 36 individuals with past alcohol dependence, but currently sober at least 2 months; and 3) 79 individuals reporting minimal use of peyote, alcohol, or other substances. We administered a screening interview, the Rand Mental Health Inventory (RMHI), and ten standard neuropsychological tests of memory and attentional/executive functions.

Results: Compared to Navajos with minimal substance use, the peyote group showed no significant deficits on the RMHI or any neuropsychological measures, whereas the former alcoholic group showed significant deficits (p < .05) on every scale of the RMHI and on two neuropsychological measures. Within the peyote group, total lifetime peyote use was not significantly associated with neuropsychological performance.

Conclusions: We found no evidence of psychological or cognitive deficits among Native Americans using peyote regularly in a religious setting. It should be recognized, however, that these findings may not generalize to illicit hallucinogen users.”

Authors: John H. Halpern, Andrea R. Sherwood, James I. Hudson, Deborah Yurgelun-Todd & Harrison G. Pope

Summary

NAC members accept peyote as a God-given medicine offering spiritual and physical healing, and abstain from alcohol and other drugs except for smoking tobacco at times of prayer.

Mescaline is a hallucinogen that is partially homologous to LSD. It has the lowest potency of the orally active naturally-derived hallucinogens, but a long duration of action, with peak effects 2 to 4 hours after consumption, declining over the next 8 hours. Mescaline, like psilocybin and LSD, acts as a partial agonist of 5-HT2a receptors in the central nervous system.

Peyote is also reputed to be an effective treatment for alcoholism when used in the NAC religious context. This is supported by anthropological reports from other traditional societies, by animal studies using ibogaine, and by human studies using LSD.

We approached members of the Navajo Nation to perform psychological and neuropsychological evaluations of NAC members, and recruited two comparison groups of Navajos to assess the sensitivity of our test battery.

Three groups of Navajos aged 18-45 were evaluated: one group had ingested peyote on at least 100 occasions, one group had been alcoholic for at least five years, and one group had never used any substance.

We excluded participants with a history of head injury or other medical condition that might affect cognitive function, current use of psychoactive medications, lifetime use of cocaine, stimulants, opioids, sedative-hypnotics, hallucinogens other than peyote, or hydrocarbon inhalants more than 100 times, or cannabis more than 100 times.

We specifically screened 80 potential participants for hallucinogen persisting perception disorder, but none reported this condition. We also did not hear any anecdotal descriptions of tolerance developing.

Participants who satisfied all criteria were invited to return for a battery of neuropsychological tests. These tests assessed memory and attentional/executive functions, but we focused almost entirely on nonverbal measures because we doubted the reliability of Western verbal tests in Navajo participants.

We administered a battery of neuropsychological tests to participants in the peyote group and the comparison group, and compared the results using multivariate linear regression, adjusting for age and sex. We also assessed the association between log-transformed lifetime episodes of peyote use and scores on all test measures.

Because of correlations between many test measures, some of the findings might represent chance associations.

Results

We performed baseline interviews with 311 Navajos, of whom 135 were excluded or failed to return for the neuropsychological testing visit. The peyote group showed no significant differences from the comparison group on any measure, whereas the former alcoholic group showed poorer performance on some measures.

Discussion

Long-term use of hallucinogens is not associated with adverse residual psychological or cognitive effects, at least when ingested as a bona fide sacrament. However, short-term use of hallucinogens is associated with significant psychological deficits.

The former alcoholic group displayed some significant neuropsychological deficits, but these deficits were modest. It should be noted that the former alcoholic group reported more cannabis consumption than the other two groups, although by design no participant exceeded 100 lifetime episodes of cannabis use. This study has several limitations, including possible selection effects, exclusion of participants due to current psychiatric disorders, and self-report without external validation. However, participants were screened without knowledge of the “right” answers needed for acceptance into the study, thus reducing the chances of false responses.

The findings of the present study cannot easily be ascribed to chance, because many of the measures were closely correlated with one another. However, the superior psychological functioning of the peyote group and inferior psychological functioning of the former alcoholic group may also be due to sociocultural factors.

Sixth, our test battery might not have been sensitive enough to detect residual deficits from peyote use, but we did detect significant deficits in the former alcoholic group.

Our findings have public health importance for several reasons, including reassurance for the 10,000 Native Americans who serve in the United States Armed Services who use peyote as a religious sacrament. It is not clear whether our findings would apply to other types of hallucinogens.