A Comparative Review of the Neuro- Psychopharmacology of Hallucinogen-Induced Altered States of Consciousness : The Uniqueness of Some Hallucinogens, Ümit Sayin, 2012

A Comparative Review of the Neuro- Psychopharmacology of Hallucinogen-Induced Altered States of Consciousness : The Uniqueness of Some Hallucinogens

Ümit Sayin

NeuroQuantology, June 2012, Volume 10, Issue 2,  316-340.

eISSN 1303-5150



Altered states of consciousness induced by hallucinogens (H-ASC) is still a vaguely understood phenomenon. Taken the diverse psychological effects they exert, the main mechanism of action of hallucinogens; LSD, ibogaine, THC, PCP, MDMA, methamphetamine, mescaline, psilocybin and DMT, of which psychological effects are discussed in the article, are not properly understood and explained by the modern methods of neuroscience due to the lack of vigorous research. The involvement of some receptors, such as, 5-HT2 (and probably other 5-HT receptors), glutamate and dopamine receptors, adrenergic and cannabinoid receptors, is one of the mechanisms, however it is not easy to explain such incongruent psychological effects by only receptor and neurotransmitter systems alone, since H-ASCs have, sometimes, their own unity and gestalt, unfolding the subconscious, in the “voyages” they induce, although the perception may, or may not, be distorted depending on the person, and “set and setting”. They induce visual, tactile and auditory hallucinations; synesthesia; perception of fractals, geometrical and kaleidoscopic images with vivid colors; perception of two dimensional pictures as three dimensional, animated and moving; distortions and alterations in the body perception; alterations in the perceptions of temporal-spatial continuum and time; changes in the perception of the ego and the self; feelings of unification with nature and universe, peak experiences – mimicking satori or nirvana-, ecstasy, rapture, extreme euphoria, excitement and happiness, oceanic bliss, self-fulfillment, referred as “good trip”, as well as, dysphoria, anxiety, mania, delirium, psychosis, acute schizophrenia, collapse of the self, known as “bad trip”; depending upon the mood, affection and psychology of the person, and “set and setting”. Mysticomimetic effects of H-ASCs, imitate the consciousness states of ancient mystics, probably, by means of activating prefrontal cortex, limbic system and the right temporal lobe. A hypothetical “holographic brain theory” may give some extra insights about the explanation of some of the effects of H-ASCs. It should be taken into account that H-ASCs, can be accepted as a good tool to investigate the nature of consciousness, brain and the human psyche, as well as some of the H-ASCs are good models of psychosis, too. More detailed scientific research should be performed to understand the basic and real mechanisms of H-ASCs, to comprehend and unravel the mystery of human mind and consciousness, since scientific medical research on hallucinogens has been legalized since 1992.

Key Words : Altered states of consciousness, Hallucinogen, LSD, ibogaine, PCP, THC, MDMA, Methamphetamine, Mescaline, Psilocybin, DMT



Hallucinogen induced trance states and altered states of consciousness (H-ASC) have been practiced in different cultures and shamanist groups all over the world for centuries (Kripper, 2011; Metzner, 1998; Stafford, 1978). Most of the hallucinogenic drugs have been characterized as mimicking psychosis and they have been coined as ‘psychotomimetics’, however there is an increasing number of researchers who are using the term ‘psychedelics’, meaning ‘mind manifesting and/or mind expanding’ (Mithoefer, 2011; Gray, 2010; Hintzen, 2010; Passie, 2008; Metzner, 1971; 1989; 1999; 2002; Grof, 2001; Shulgin, 1991; 1997; Tart, 1990; Stafford, 1978). While the debate about the terminology still continues in many scientific circles, it is not quite established whether these natural or synthetic chemicals are really ‘manifesting and expanding mind and human psyche’ or not. However, it is obvious that hallucinogens affect conscious states (Hintzen, 2010; Austin, 1999; Siegel, 1992; Shulgin, 1991-1997; Tart, 1990; Stevens, 1988; Lee, 1985; Stafford, 1978); EEG (Brimblecombe, 1973; Fried, 1977; Shagas, 1966; Brazier, 1964), human psychology and behavior (Hintzen, 2010; Passie, 2008; Fantegrossi, 2008; Popik, 1998; Henderson and Glass, 1994; Pletscher, 1993; Tart, 1990; Stafford, 1978), while there has been some attempts to use these psychedelic drugs in psychotherapy (Grof, 2001; Tart, 1990) and in the treatment of heroin addiction (Popik, 1995; 1998).

Altered states of consciousness’ is a widely used term to define a deviation from the normal and regular mind state into a hyper or hypo excitation state. It has been proposed that altered states of consciousness
can be attained through various methods, such as Zen meditation (Austin, 1999), expanded sexual response (ESR) (Sayin, 2011; Taylor, 2000; 2002), hypnosis (Ross, 2006; Tart, 1990; Ludwig, 1965 ), metabolic changes (Hobson, 1994; Tart, 1990; ), sensory deprivation (Lilly, 1972; Tart, 1990), hallucinogenic drugs (Brunton, 2010; Hardman, 2001; Shulgin, 1991; 1997; Tart, 1990; Grof, 1985; 2001; Goodman, 1980; Stafford, 1978; Brimblecombe, 1973), central nervous system (CNS) stimulants (Rothman, 2001; Hobson, 1994; Tart, 1990; Nielsen, 1988 ), physiological sleep (Hobson, 1988; Tart, 1990), anesthetic drugs (PCP, Ketamine) (Tart, 1990; Stafford, 1978), etc. Although involvement of many receptor and neurotransmitter systems have been proposed in the mechanism of action of H-ASC inducing drugs, there has been no consensus on the basic mechanisms of some particular effects of some hallucinogenic drugs, such as LSD, ibogaine, THC (tetrahydrocannabinol), PCP (phencyclidine), MDMA, methamphetamine, mescaline, psilocybin, DMT and many others.

This article briefly reviews the main psychological effects of H-ASCs and the possible known mechanisms of these mind states, and discusses the uniqueness of some of the hallucinogens. The main hypothesis of this article is that H-ASCs are very drug specific, although they may act on similar receptor and neuro-transmitter systems, and cannot be investigated in a single, general ASC model which can be put into certain standard scales; namely, each hallucinogen’s effect on human psychology is unique and very specific to that particular individual, an epiphenomenon that seems to violate the deterministic principals of neurochemistry, because of the unpredictable psychological effects of H-ASCs. No psychological outcome of H-ASCs, which exert their effects in a chaotic platform, can be predicted beforehand, and can be investigated in the format of pure deterministic principals.

The psychedelic or psychotomimetic effects of many hallucinogens change from person to person (Henderson, 1994; Pletscher, 1993; Stevens 1988; Lee and Shlain, 1985; Shulgin, 1991; 1997). Even in the same person, at the same doses, a train of psychological events may be very distinct from each other at every different, successive ingestion (so called-trips!) (Hintzen, 2010; Shulgin, 1997; Henderson, 1994; Stevens 1988; Lee and Shlain, 1985). To visualize and compare H-ASCs, the psychological effects of LSD, ibogaine, THC, PCP, MDMA, methamphetamine, mescaline, psilocybin and DMT will be discussed.

One day, H-ASCs may become a powerful tool to investigate the nature of human consciousness in terms of ‘quantum mechanics’ of neuropharmacology, if these drugs have extra neuro-quantal properties to alter consciousness.