Psychedelic Dreams

Recent research illuminates the similarity of psychedelic states to dreaming.

Posted Sep 30, 2020

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Creative and logical halves of human mind.
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Each day, we regularly pass through a number of different states of awareness. These states are, broadly speaking, wakefulness and sleep, with both wakefulness and sleep containing multiple substates of their own. The degree of awareness and the emotional quality of the waking state varies over the course of the day as we pass from periods of focused attention to daydreaming and on to periods of drowsiness where consciousness begins to become unfocused. Wakefulness is characterized by an awareness of the external environment and the ability to respond behaviorally to changes in it. After a period of about 16 hours of wakefulness, we are ready to enter a very different state, that of sleep. 

Sleep is a period of varying degrees of disconnection from the external environment with limited ability to react behaviorally to changes in it. Sleep itself can be further divided into a number of well-known states that are distinguished by characteristic EEG patterns and the experienced depth of sleep. These have been termed stage 1, that is very light in depth, stage 2, that is of average depth, stage 3, that is deep and where there is a great degree of disconnection from the external environment, and REM, or rapid eye movement sleep, during which the most vivid dreaming occurs. In REM sleep, a paradoxical state exists in which certain areas of the brain appear to be nearly awake at the same time the body is paralyzed and is non-responsive to the external world. 

These waking and sleeping states are typical and we experience them on a daily basis. There are also states of consciousness that we can experience while awake that are distinctly different from the usual waking state and they actually bear some resemblance to the dream state that occurs during REM sleep. These have been called altered states of consciousness (ASC) and include, among many others, states of hallucination, trance, meditation, hypnosis, and intoxication with certain kinds of psychoactive drugs (Ember & Carolus, 2017).

The drugs most associated with creating ASCs are known as hallucinogens or psychedelics. The term hallucinogen is somewhat misleading, as these substances only infrequently occasion proper hallucinations in which the person does not realize that what is being experienced has no basis in external reality. More often these substances give rise to profound alterations of sensations, thought processes, and emotions that the person understands are being caused by the substance. 

Oliver Sacks, the famous neurologist, gave an example of a proper hallucination that he experienced under the influence of Artane, a synthetic drug that is similar to belladonna (Sacks, 2012, p. 106-109). He describes how he took a significant dose of the drug and waited for something to happen but only found his vision became somewhat blurry and he had difficulty reading. Nothing else seemed to happen. Then two of his friends knocked on his front door, he invited them in, asked what they wanted for breakfast, and prepared it for them while talking to them. When he took the breakfast into where they were sitting, he found an empty room. He was stunned by the realization that they had never been there. He was frightened because, in his experiences with other drugs, such as LSD, he had always known what was happening, even as the world was transformed, but with this drug, the experience seemed totally real and he could not tell until later that it had not actually occurred. Before the drug wore off, he had several more experiences after the one described above, including some involving nonexistent helicopters and talking spiders. 

There is considerable debate about which drugs should be considered hallucinogens, and you can find many different classification schemes that consider chemical structures, brain receptors affected, and the phenomenology of the states produced to decide whether or not to include a drug in this category. The term psychedelic, which is often, but not always used synonymously with a hallucinogen, was coined by Humphry Osmond in 1956 and is derived from the Greek words psyche (mind) and delos (visible) and literally means “mind manifesting” or “mind revealing” (Grinspoon & Baklar, 1979). Groups of substances that have this property of revealing mental processes and are included by one authority or another as hallucinogens are the psychedelics, entactogens/empathogens, cannabinoids, dissociatives, and deliriants. These substances have historical, cultural, and phenomenological connections and have long been included in the category of hallucinogens (see Grinspoon & Baklar, 1979). 

The substances that most fully provide the psychedelic experience without significant additional effects, such as the kind of delirium reported by Dr. Sacks above, have been termed the “classic hallucinogens” or “classic psychedelics." This group of drugs primarily act as agonists or partial agonists on a subtype of serotonin receptors known as the 5-HT2AR (Nichols, 2016). Prominent members of this category are LSD, psilocybin, mescaline, and DMT. These substances have the ability to significantly change mental functioning in a way that illuminates aspects of mental functioning or, as Grof (1975) noted, these drugs act as a “non-specific amplifier of the unconscious”.

They are currently under active investigation as potential treatments for a host of psychiatric problems, including treatment-resistant depression, anxiety associated with terminal illness, drug addiction, and PTSD (Pollan, 2018). Most cultures throughout history and around the planet have used altered states of consciousness as ways of gaining knowledge, transcending day-to-day experience, and healing illness. Today modern Western science is investigating these as tools for transcendence and healing

As I noted above, many altered states of consciousness, including states produced by this class of drugs, remind us of the dream state. Do they, in fact, produce an experience that could be described as a kind of waking dream? A connection certainly exists between the underlying neural structures of dreaming and the psychedelic state produced by psychedelic drugs.

As we know, dreaming occurs as a result of the coordinated actions of certain brain subsystems. Major areas involved include the pontine tegmentum, thalamic nuclei, and the limbic system. While these areas are more active during dreaming, the dorsolateral prefrontal cortex, the parietal cortex, and the posterior cingulate cortex show decreased activity. There is also greater functional integration between temporal-occipital areas with the amygdala than occurs in wakefulness. So the visual aspects of dreaming are related to the temporal-occipital cortical areas while activity between the limbic system and the orbitofrontal cortex is associated with the emotional aspects of dreams.

It is therefore interesting to note that the processes that bring about dreaming are associated with activity in the 5HT2AR system. The deactivation of these areas in the prefrontal cortex may be mediated, to some degree, by 5HT2AR activity. 5HT2A receptors are present in significant densities in neurons that project into the prefrontal cortex and sensory association areas of the cortex. Serotonergic psychedelics have their primary action at the 5HT2A receptors. The effect of these drugs is the downregulation of dorsolateral prefrontal activity along with the upregulation of the sensory association areas. This is very close to what happens during dreaming.

So we have the long-standing recognition of the similarity between the ASC brought about by psychedelic drugs and REM sleep dreaming as well as some interesting neuroscience findings that show a potential association between the brain mechanisms behind both dreaming and these ASC. But does the phenomenology of dreaming really resemble that of psychedelic drug experiences? A recent article has addressed this question using an interesting methodology (Sanz, Zamberlan, Erowid, Erowid, & Tagliazucchi, 2018). 

This study investigated the semantic similarity between a large group of subjective reports of the mental effects of a number of psychoactive substances and a large number of subjective reports of what they termed high and low lucidity dreams. This was done by comparing psychoactive substance experience reports that users have posted to the drug information website Erowid and similar reports of dream experiences that have been posted to the website Dream Journal. Erowid has been available since the 1990s and is a great source of information on psychoactive substances. It is consulted by professionals and the lay public alike. Dream Journal allows people to create and, if they want, to post their own dream journals. As a result, we now have thousands of first person reports of psychoactive drug experiences and dreams available for study.

The methodology used was complex and required significant work to take the raw reports and make them accessible to statistical analysis. If you have an interest in how this was done, a full explanation can be found in the study, which is open access and available to anyone with an internet connection. In brief, the analysis looked for associations across reports in the terms used. It turned out that the most frequent associations between psychedelic drug reports and dream reports related to perceptions, emotions, settings, and relatives. 

They considered lucid dreams to be those in which the dreamer is aware of being in a dream rather than in a state of wakefulness and identifies with the waking rather than the dreaming self. Low lucidity dreams, in contrast, were considered to be those in which there is a loss of the sense of personal agency and control with “a dissociation between the first-person point of view and the bodily self of the dreamer” (Sanz et al, 2018, p. 2), decreased high-level cognitive function, and increased emotional reactivity. They looked for the degree of semantic similarity between the drug experience reports and the dream reports. 

There were 165 different substances reviewed from the Erowid reports. These substances could be characterized as being serotonergic psychedelics, entactogens (such as MDMA, known on the street as “Ecstasy” or “Molly," that cause increased awareness of sensations and foster a feeling of connectedness to others), dissociatives (such as PCP and Ketamine), deliriants, depressant/sedatives, stimulants, antipsychotics/antidepressants, monoamine inhibitors (sometimes used as antidepressants), oneirogens (substances causing dreams), and other. Each drug could be considered to be in up to two categories depending on its effects.

The top five drugs that were associated with experience reports that shared the greatest similarity to high lucidity dreams were, from first to last: LSD, L. williamsii (peyote), Datura (a deliriant containing plant), Psilocybin mushrooms, and Cannabis (marijuana). The top five for low lucidity dreams were: Datura, LSD, Brugmansia (a deliriant containing plant), L. williamsii, and Cannabis. LSD, L. williamsii, and Psilocybin mushrooms belong to the classical psychedelic (serotonergic) category, Datura and Brugmansia to the deliriant category (the same one that produced Dr. Sacks’ hallucinations), and Cannabis, which can be considered a depressant/sedative, other, or as above, a substance with some psychedelic properties. MDMA, an entactogen, and Ketamine, a dissociative, along with other substances in these categories ranked in the top 20 substances as well. Drugs with the least association with high lucidity dream reports were barbiturates (used in the past as sleeping medication), antidepressants, and pain medications. The list was similar for low lucidity dream reports. About 80% of the top 20 substances were serotonergic psychedelics, dissociative hallucinogens, or deliriant hallucinogens. If you count, as they did not, Cannabis, MDMA, and Salvia divinorum (often considered an atypical psychedelic due to its unique action on the kappa opioid receptors) as hallucinogens, it is 100%. None of the lowest ranking substances were from the broad category of hallucinogens, as defined above.  

"Yin and Yang" by Klem - This vector image was created with Inkscape by Klem, and then manually edited by Mnmazur.. Licensed under Public Domain via Wikimedia Commons
Source: "Yin and Yang" by Klem - This vector image was created with Inkscape by Klem, and then manually edited by Mnmazur.. Licensed under Public Domain via Wikimedia Commons

We now have information from the historical use of these substances to produce ASC, neuroscience findings, and phenomenological research, that there is indeed a significant similarity between the dreaming state and the states occasioned by the group of drugs that have been labeled hallucinogens. These drugs appear to have significant therapeutic potential as the psychedelics are being investigated as treatments for terminal cancer-related anxiety, the dissociative drug Ketamine for treatment-resistant depression, and MDMA and Cannabis for PTSD. Even the extremely dangerous deliriant drugs have had their role. For example, the founder of Alcoholics Anonymous, Bill Wilson, had a powerful mystical experience while being treated with the hallucinogen belladonna, stopped drinking, and founded AA. 

The brain systems that underlie dreaming and result in a loosening of rational control, an experience of extraordinary perceptions, and enhanced emotionality, will be an important focus of study in future explorations of how both hallucinogenic substances and dreamwork can help in healing a variety of psychiatric illnesses. This is an exciting avenue for future research and clinical service.


Ember, Carol R., Christina Carolus. 2017. “Altered States of Consciousness” in C. R. Ember, ed. Explaining Human Culture. Human Relations Area Files, accessed 09/28/2020

Grinspoon, L., & Bakalar, J.B. (1979). Psychedelic drugs reconsidered. New York: Basic Books, Inc.

Grof, S. (1975). Realms of the human unconscious: Observations from LSD research. New York: Basic Books, Inc. 

Nichols D. E. (2016). Psychedelics. Pharmacological reviews68(2), 264–355.

Pollan, M. (2018). How to Change Your Mind: What the New Science of Psychedelics Teaches Us About Consciousness, Dying, Addiction, Depression, and Transcendence. New York: Penguin Press.

Sacks, O. (2012). Hallucinations. New York: Vintage Books.

Sanz, C., Zamberlan, F., Erowid, E., Erowid, F., & Tagliazucchi, E. (2018). The Experience Elicited by Hallucinogens Presents the Highest Similarity to Dreaming within a Large Database of Psychoactive Substance Reports, Frontiers in Neuroscience12, p. 1 -7,