Hallucinogens fall into several different classes, as broadly defined by pharmacological mechanism of action, and chemical structure. These include psychedelics, entactogens, dissociatives, and other atypical hallucinogens. Although these classes do not share a common primary mechanism of action, they do exhibit important similarities in their ability to occasion temporary but profound alterations of consciousness, involving acute changes in somatic, perceptual, cognitive, and affective processes. Such effects likely contribute to their recreational use. However, a growing body of evidence indicates that these drugs may have therapeutic applications beyond their potential for abuse. This review will present data on several classes of hallucinogens with a particular focus on psychedelics, entactogens, and dissociatives, for which clinical utility has been most extensively documented. Information on each class is presented in turn, tracing relevant historical insights, highlighting similarities and differences between the classes from the molecular to the behavioral level, and presenting the most up-to-date information on clinically oriented research with these substances, with important ramifications for their potential therapeutic value.
Garcia-Romeu, A., Kersgaard, B., & Addy, P. H. (2016). Clinical applications of hallucinogens: A review. Experimental and clinical psychopharmacology, 24(4), 229. 10.1037/pha0000084 Link to full text
Lysergic acid N,N-diethylamide (LSD) is perhaps one of the most intriguing psychoactive substances known and numerous analogs have been explored to varying extents in previous decades. In 2013, N6-allyl-6-norlysergic acid diethylamide (AL-LAD) and (2’S,4’S)-lysergic acid 2,4-dimethylazetidide (LSZ) appeared on the ‘research chemicals’/new psychoactive substances (NPS) market in both powdered and blotter form. This study reports the analytical characterization of powdered AL-LAD and LSZ tartrate samples and their semi-quantitative determination on blotter paper. Included in this study was the use of nuclear magnetic resonance (NMR) spectroscopy, gas chromatography-mass spectrometry (GC-MS), low and high mass accuracy electrospray MS(/MS), high performance liquid chromatography diode array detection and GC solid-state infrared analysis. One feature shared by serotonergic psychedelics, such as LSD, is the ability to mediate behavioural responses via activation of 5-HT2A receptors. Both AL-LAD and LSZ displayed LSD-like responses in male C57BL/6 J mice when employing the head-twitch response (HTR) assay. AL-LAD and LSZ produced nearly identical inverted-U-shaped dose-dependent effects, with the maximal responses occurring at 200 µg/kg. Analysis of the dose responses by nonlinear regression confirmed that LSZ (ED50 = 114.2 nmol/kg) was equipotent to LSD (ED50 = 132.8 nmol/kg) in mice, whereas AL-LAD was slightly less potent (ED50 = 174.9 nmol/kg). The extent to which a comparison in potency can be translated directly to humans requires further investigation. Chemical and pharmacological data obtained from NPS may assist research communities that are interested in various aspects related to substance use and forensic identification.
Brandt, S. D., Kavanagh, P. V., Westphal, F., Elliott, S. P., Wallach, J., Colestock, T., … & Halberstadt, A. L. (2016). Return of the lysergamides. Part II: Analytical and behavioural characterization of N6‐allyl‐6‐norlysergic acid diethylamide (AL‐LAD) and (2’S, 4’S)‐lysergic acid 2, 4‐dimethylazetidide (LSZ). Drug testing and analysis. http://dx.doi.org/10.1002/dta.1985 Link to full text
Lysergic acid diethylamide (LSD) is used recreationally and has been evaluated as an adjunct to psychotherapy to treat anxiety in patients with life-threatening illness. LSD is well-known to induce perceptual alterations, but unknown is whether LSD alters emotional processing in ways that can support psychotherapy. We investigated the acute effects of LSD on emotional processing using the Face Emotion Recognition Task (FERT) and Multifaceted Empathy Test (MET). The effects of LSD on social behavior were tested using the Social Value Orientation (SVO) test. Two similar placebo-controlled, double-blind, random-order, cross-over studies were conducted using 100 μg LSD in 24 subjects and 200 μg LSD in 16 subjects. All of the subjects were healthy and mostly hallucinogen-naive 25- to 65-year-old volunteers (20 men, 20 women). LSD produced feelings of happiness, trust, closeness to others, enhanced explicit and implicit emotional empathy on the MET, and impaired the recognition of sad and fearful faces on the FERT. LSD enhanced the participants’ desire to be with other people and increased their prosocial behavior on the SVO test. These effects of LSD on emotion processing and sociality may be useful for LSD-assisted psychotherapy.
Dolder, P. C., Schmid, Y., Müller, F., Borgwardt, S., & Liechti, M. E. (2016). Lsd acutely impairs fear recognition and enhances emotional empathy and sociality. Neuropsychopharmacology. http://dx.doi.org/10.1038/npp.2016.82 Link to full text
Over the 1950s and early 1960s, the use of the hallucinogenic drug lysergic acid diethylamide (LSD) to facilitate psychotherapy was a promising field of psychiatric research in the USA. However, during the 1960s, research began to decline, before coming to a complete halt in the mid-1970s. This has commonly been explained through the increase in prohibitive federal regulations during the 1960s that aimed to curb the growing recreational use of the drug. However, closely examining the Food and Drug Administration’s regulation of LSD research in the 1960s will reveal that not only was LSD research never prohibited, but that the administration supported research to a greater degree than has been recognized. Instead, the decline in research reflected more complex changes in the regulation of pharmaceutical research and development.
Oram, M. (2016). Prohibited or regulated? LSD psychotherapy and the United States Food and Drug Administration. History of psychiatry, 0957154X16648822. Link to full text
Personality is known to be relatively stable throughout adulthood. Nevertheless, it has been shown that major life events with high personal significance, including experiences engendered by psychedelic drugs, can have an enduring impact on some core facets of personality. In the present, balanced-order, placebo-controlled study, we investigated biological predictors of post-lysergic acid diethylamide (LSD) changes in personality. Nineteen healthy adults underwent resting state functional MRI scans under LSD (75µg, I.V.) and placebo (saline I.V.). The Revised NEO Personality Inventory (NEO-PI-R) was completed at screening and 2 weeks after LSD/placebo. Scanning sessions consisted of three 7.5-min eyes-closed resting-state scans, one of which involved music listening. A standardized preprocessing pipeline was used to extract measures of sample entropy, which characterizes the predictability of an fMRI time-series. Mixed-effects models were used to evaluate drug-induced shifts in brain entropy and their relationship with the observed increases in the personality trait openness at the 2-week follow-up. Overall, LSD had a pronounced global effect on brain entropy, increasing it in both sensory and hierarchically higher networks across multiple time scales. These shifts predicted enduring increases in trait openness. Moreover, the predictive power of the entropy increases was greatest for the music-listening scans and when “ego-dissolution” was reported during the acute experience. These results shed new light on how LSD-induced shifts in brain dynamics and concomitant subjective experience can be predictive of lasting changes in personality.
The question of how spatially organized activity in the visual cortex behaves during eyes-closed, lysergic acid diethylamide (LSD)-induced “psychedelic imagery” (e.g., visions of geometric patterns and more complex phenomena) has never been empirically addressed, although it has been proposed that under psychedelics, with eyes-closed, the brain may function “as if” there is visual input when there is none. In this work, resting-state functional connectivity (RSFC) data was analyzed from 10 healthy subjects under the influence of LSD and, separately, placebo. It was suspected that eyes-closed psychedelic imagery might involve transient local retinotopic activation, of the sort typically associated with visual stimulation. To test this, it was hypothesized that, under LSD, patches of the visual cortex with congruent retinotopic representations would show greater RSFC than incongruent patches. Using a retinotopic localizer performed during a nondrug baseline condition, nonadjacent patches of V1 and V3 that represent the vertical or the horizontal meridians of the visual field were identified. Subsequently, RSFC between V1 and V3 was measured with respect to these a priori identified patches. Consistent with our prior hypothesis, the difference between RSFC of patches with congruent retinotopic specificity (horizontal-horizontal and vertical-vertical) and those with incongruent specificity (horizontal-vertical and vertical-horizontal) increased significantly under LSD relative to placebo, suggesting that activity within the visual cortex becomes more dependent on its intrinsic retinotopic organization in the drug condition. This result may indicate that under LSD, with eyes-closed, the early visual system behaves as if it were seeing spatially localized visual inputs.
Roseman, L., Sereno, M. I., Leech, R., Kaelen, M., Orban, C., McGonigle, J., … & Carhart‐Harris, R. L. (2016). LSD alters eyes‐closed functional connectivity within the early visual cortex in a retinotopic fashion. Human Brain Mapping. http://dx.doi.org/10.1002/hbm.23224
Psychedelic drugs such as lysergic acid diethylamide (LSD) were used extensively in psychiatry in the past and their therapeutic potential is beginning to be re-examined today. Psychedelic psychotherapy typically involves a patient lying with their eyes-closed during peak drug effects, while listening to music and being supervised by trained psychotherapists. In this context, music is considered to be a key element in the therapeutic model; working in synergy with the drug to evoke therapeutically meaningful thoughts, emotions and imagery. The underlying mechanisms involved in this process have, however, never been formally investigated. Here we studied the interaction between LSD and music-listening on eyes-closed imagery by means of a placebo-controlled, functional magnetic resonance imaging (fMRI) study. Twelve healthy volunteers received intravenously administered LSD (75 µg) and, on a separate occasion, placebo, before being scanned under eyes-closed resting conditions with and without music-listening. The parahippocampal cortex (PHC) has previously been linked with (1) music-evoked emotion, (2) the action of psychedelics, and (3) mental imagery. Imaging analyses therefore focused on changes in the connectivity profile of this particular structure. Results revealed increased PHC–visual cortex (VC) functional connectivity and PHC to VC information flow in the interaction between music and LSD. This latter result correlated positively with ratings of enhanced eyes-closed visual imagery, including imagery of an autobiographical nature. These findings suggest a plausible mechanism by which LSD works in combination with music listening to enhance certain subjective experiences that may be useful in a therapeutic context.
Kaelen, M., Roseman, L., Kahan, J., Santos-Ribeiro, A., Orban, C., Lorenz, R., … & Wall, M. B. (2016). LSD modulates music-induced imagery via changes in parahippocampal connectivity. European Neuropsychopharmacology. http://dx.doi.org/10.1016/j.euroneuro.2016.03.018 Link to full text
Once again researchers from the Psychedelic Research Programme jointly set up by the Beckley Foundation and Imperial College London have published trailblazing research on the effects of psychedelics on the brain. These trendsetting studies are the first to apply multimodal neuroimaging to subjects who were injected with LSD. Dr. Carhart-Harris and his fellow colleagues from Imperial College London have revealed the effects of lysergic acid diethylamide (LSD) on the brain’s network communication, blood flow and electrical activity using fMRI BOLD, arterial spin labelling and magnetoencephalography (Carhart-Harris et al., 2016).
From these neuroimaging studies, researchers have gained an important and novel insight into the basis of ego-dissolution, the way in which closed-eye visuals occur and effects of the combination of LSD and music in the brain. The studies were conducted with 20 subjects who were injected once with 75µg LSD and once with a placebo, at least two weeks apart. All participants had prior experience with psychedelics.
Functional magnetic resonance imaging (fMRI) based on the evaluation of blood oxygen level dependent (BOLD) contrast was applied to evaluate the activity of different brain regions and their interconnection while on LSD. The scans were performed in the resting state, i.e. in the absence of any external stimuli or specific cognitive tasks. Subsequently the levels of (dis)integration/(de)segregation were evaluated, with certain regions of interest (ROI) being picked up to analyse their interaction with the other brain regions.
Average functional connectivity density (FCD) in cortical and subcortical regions under the placebo and LSD conditions – Tagliazucchi et al., 2016.
One of the main findings of the study was that LSD facilitates an inflation of globalised communication between various brain regions. Using positron emission tomography (PET), the researchers found that the highest level of such communication occurred in the regions with the highest density of serotonin-2A (5-HT2A) receptors, LSD acting as an agonist to this type of receptors. One interesting aspect of this is that the higher interaction between brain regions corresponded with lower integration within certain networks. All in all, the study identified 12 resting state networks affected by LSD in this way, with the default mode network (DMN) being the most important for the case at study.
Ego dissolution
The DMN is the network of the brain that becomes activated when a person is experiencing resting states such as daydreaming, and becomes inactivated during goal-oriented tasks. According to the present study, the disintegration within the DMN is directly related to the onset of a state of consciousness commonly described as ego dissolution. Ego dissolution is the subjective experience of losing one’s sense of identity. It is sometimes described as unity with the outside world and oneness with the universe resulting from a blurring of the boundaries of the autonomous self. The altered state of consciousness questionnaire used at the end of each scanning day revealed that ego dissolution correlated with the experience of altered meaning, i.e. attaching importance to objects previously deemed unimportant and giving surroundings new, alien meaning. Also correlated with the state of ego dissolution was disintegration in other brain regions such as the salience network and the thalamus.
Brain regions where a significant correlation between FCD and subjective reports of ego dissolution (LSD minus placebo) was found are colored in red. Brain regions presenting the most selective correlations between FCD increases and ego dissolution scores are colored in green – Tagliazucchi et al., 2016
Disintegration in the DMN and other resting networks was also accompanied by decreased alpha power in regions such as the posterior cingulate cortex (PCC). Regular alpha oscillations are hypothesised to inhibit spontaneous neuronal activity, i.e. that which occurs without exposure to particular stimuli (Tagliazucchi et al., 2016). LSD was found to decrease alpha power and thus trigger spontaneous activity in neurons, an effect that could partially explain the closed-eye imagery associated with the LSD experience.
The mechanisms of closed-eye imagery
Striking results were obtained in the study of closed-eye imagery induced by LSD. The researchers investigated both simple images like geometrical patterns and complex ones including autobiographical scenes occurring under LSD. The study revealed that although there was no visual input, under LSD the visual cortex (VC) behaved as if there was (Carhart-Harris et al., 2016). This observation supports ongoing theories that the appearance of geometrical imagery may be caused by the rendered instability of the VC (Butler et al., 2011).
Apart from the increase in blood flow level, the visual cortex also displayed increased functional connectivity with other brain regions, mainly the parahippocampal cortex (PHC), typically involved in memory retrieval, music-evoked emotion and mental imagery. The researchers used a Dynamic Causal Modelling analysis to reveal increased effective connectivity between the VC and the PHC, where the PHC triggered the activity of the VC. The interconnection of these brain regions can be held responsible for the “colouring” of personal recollections experienced by the subjects under LSD. Apart from the PHC, other brain regions such as those in occipital and inferior frontal lobes also became activated during visuals, leading to the conclusion that a much larger portion of the brain is involved in producing imagery under LSD than in the normal waking state.
The influence of music
The study further revealed the highly important role of music during the psychedelic experience. Mendel Kaelen, a PhD candidate at Imperial College London and board member of the OPEN Foundation, explored the synergistic effects of music during the LSD experience (Kaelen et al., 2016). Three fMRI scans were performed, the first and the third of which were done without the use of music, the second being performed while the subjects listened to music (two excerpts from the album Yearning by the ambient artist Robert Rich and the Indian classical musician Lisa Moscow).
The study showed that the PHC becomes highly activated when subjects are exposed to music and LSD. Furthermore, the increase of interaction between the PHC and the visual cortex corresponded with the intensity of the closed-eye visuals, both simple (geometrical patterns) and complex ones (e.g. based on personal recollections). This certainly underscores the importance of incorporating music into LSD-assisted psychotherapy.
Expanding the knowledge
The findings of the present study with LSD provide firmer ground to the knowledge that has been gathered in experiments using other psychedelics. Psilocybin has been found to have similar effects on brain activity including the disintegration in certain regions such as the default mode network and the emergence of new connections between normally segregated networks. These conclusions emerged from two independent researches, one of which was performed by the authors of the present LSD study (Carhart-Harris et al., 2012, Kometer et al., 2015). Still another research group discovered analogous effects of the Amazonian psychedelic ayahuasca on the human brain (Riba et al., 2002).
The findings of this groundbreaking study have several important implications. First, they hint at a neurological understanding of the therapeutic potential of LSD. Due to its “entropic” effect on the brain – the increase of disintegration within and simultaneous increase of interaction between certain brain regions – LSD may hold the potential for breaking down pathological patterns associated with depression, for instance, and thus increasing the effectiveness of psychotherapy.
The study also demonstrated the potential of LSD in the study of the neurobiology of consciousness, as it seems to put subjects into the so-called primary state of consciousness characteristic of the earlier stages of consciousness development in children, of REM sleep and of early psychosis (Carhart-Harris et al., 2016). This also means that LSD could be applied in psychological research in the study of pathologies (Carhart-Harris et al., 2016).
Apart from the short-term effects of LSD on brain chemistry, more investigation is warranted on the potential of the LSD experience to provoke sustainable changes in personality.
Butler T. C., Benayoun M., Wallace E., van Drongelen W., Goldenfeld N. and Cowan J. (2012) Evolutionary constraints on visual cortex architecture from the dynamics of hallucinations. Proceedings of the National Academy of Sciences of the United States of America, 606-609. https://dx.doi.org/10.1073/pnas.1118672109
Carhart-Harris R. L., Errizoe D., Williams T., Stone J. M., Reed L. J., Colasanti A., Tyacke R.J., Leech R., Malizia A.L., Murphy K., Hobden P., Evans J., Feilding A., Wise R.G. and Nutt D.J. (2012) Neural correlates of the psychedelic state as determined by fMRI studies with psilocybin. Proc. Natl. Acad. Sci. USA 109, 2138–2143. https://dx.doi.org/10.1073/pnas.1119598109
Carhart-Harris R. L., Muthukumaraswarmy S., Roseman L., Kaelen M., Droog W., Murphy K., Taggliazzuchi E., Schenberg E.E., Nest T., Orban C., Leech R., Williams, L., Williams T., Bolstridge M., Sessa B., McGoniglea J., Sereno M., Nichols D., Hellyer P.J., Hobden P., Evans J., Singh K.D., Wise R.G., Curran V., Feilding A. and Nutt D.J. (2016) Neural Correlates of the LSD Experience Revealed by Multimodal Neuroimaging. Proceedings of the National Academy of Sciences of the United States of America, 1-6. https://dx.doi.org/10.1073/pnas.1518377113
Kaelen M., Roseman L., Kahan J., Santos-Ribeiro A., Orban C., Lorenz R., Barett F.S., Bolstridge M., Williams T., Williams L., Wall M.B., Feilding A., Muthukumuraswamy S., Nutt D.J and Carhart-Harris, R. (2016) LSD modulates music-induced imagery via changes in the parahippocampal connectivity. European Neuropsychopharmacology, 1-10. http://dx.doi.org/10.1016/j.euroneuro.2016.03.018
Kometer M., Pokorny T., Seifritz E. and Vollenweider F.X. (2015) Psilocybin-induced spiritual experiences and insightfulness are associated with synchronization of neuronal oscillations. Psychopharmacology (Berl) 232(19):3663–3676. https://dx.doi.org/10.1007/s00213-015-4026-7
Riba J., Anderer P., Morte A., Urbano G., Jané F., Saletu B. and Barbanoj M.J. (2002) Topographic pharmaco-EEG mapping of the effects of the South American psychoactive beverage ayahuasca in healthy volunteers. Br J Clin Pharmacol 53(6):613–628. https://dx.doi.org/10.1046/j.1365-2125.2002.01609
Tagliazucchi E., Roseman L., Kaelen M., Orban C., Muthukumaraswamy S. D., Murphy K., Laufs H., Leech R., McGonigle J., Crossley N., Bullmore E., Williams T., Bolstridge M., Feilding A., Nutt D.J. and Carhart-Harris R. (2016) Increased Global Functional Connectivity Correlates with LSD-Induced Ego Dissolution. Current Biology, 26, 1-8. http://dx.doi.org/10.1016/j.cub.2016.02.010
Lysergic acid diethylamide (LSD) is the prototypical psychedelic drug, but its effects on the human brain have never been studied before with modern neuroimaging. Here, three complementary neuroimaging techniques: arterial spin labeling (ASL), blood oxygen level-dependent (BOLD) measures, and magnetoencephalography (MEG), implemented during resting state conditions, revealed marked changes in brain activity after LSD that correlated strongly with its characteristic psychological effects. Increased visual cortex cerebral blood flow (CBF), decreased visual cortex alpha power, and a greatly expanded primary visual cortex (V1) functional connectivity profile correlated strongly with ratings of visual hallucinations, implying that intrinsic brain activity exerts greater influence on visual processing in the psychedelic state, thereby defining its hallucinatory quality. LSD’s marked effects on the visual cortex did not significantly correlate with the drug’s other characteristic effects on consciousness, however. Rather, decreased connectivity between the parahippocampus and retrosplenial cortex (RSC) correlated strongly with ratings of “ego-dissolution” and “altered meaning,” implying the importance of this particular circuit for the maintenance of “self” or “ego” and its processing of “meaning.” Strong relationships were also found between the different imaging metrics, enabling firmer inferences to be made about their functional significance. This uniquely comprehensive examination of the LSD state represents an important advance in scientific research with psychedelic drugs at a time of growing interest in their scientific and therapeutic value. The present results contribute important new insights into the characteristic hallucinatory and consciousness-altering properties of psychedelics that inform on how they can model certain pathological states and potentially treat others.
Carhart-Harris, R. L., Muthukumaraswamy, S., Roseman, L., Kaelen, M., Droog, W., Murphy, K., … & Leech, R. (2016). Neural correlates of the LSD experience revealed by multimodal neuroimaging. Proceedings of the National Academy of Sciences, 201518377. http://dx.doi.org/10.1073/pnas.1518377113 Link to full text
Lysergic acid diethylamide (LSD) is a non-selective serotonin-receptor agonist that was first synthesized in 1938 and identified as (potently) psychoactive in 1943. Psychedelics have been used by indigenous cultures for millennia [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][1]; however, because of LSD’s unique potency and the timing of its discovery (coinciding with a period of major discovery in psychopharmacology), it is generally regarded as the quintessential contemporary psychedelic [2]. LSD has profound modulatory effects on consciousness and was used extensively in psychological research and psychiatric practice in the 1950s and 1960s [3]. In spite of this, however, there have been no modern human imaging studies of its acute effects on the brain. Here we studied the effects of LSD on intrinsic functional connectivity within the human brain using fMRI. High-level association cortices (partially overlapping with the default-mode, salience, and frontoparietal attention networks) and the thalamus showed increased global connectivity under the drug. The cortical areas showing increased global connectivity overlapped significantly with a map of serotonin 2A (5-HT2A) receptor densities (the key site of action of psychedelic drugs [4]). LSD also increased global integration by inflating the level of communication between normally distinct brain networks. The increase in global connectivity observed under LSD correlated with subjective reports of “ego dissolution.” The present results provide the first evidence that LSD selectively expands global connectivity in the brain, compromising the brain’s modular and “rich-club” organization and, simultaneously, the perceptual boundaries between the self and the environment.
Tagliazucchi, E., Roseman, L., Kaelen, M., Orban, C., Muthukumaraswamy, S. D., Murphy, K., … & Bullmore, E. (2016). Increased Global Functional Connectivity Correlates with LSD-Induced Ego Dissolution. Current Biology. http://dx.doi.org/10.1016/j.cub.2016.02.010
