Hallucinations Under Psychedelics and in the Schizophrenia Spectrum

An Interdisciplinary and Multiscale Comparison

Pantelis Leptourgos; Martin Fortier-Davy; Robin Carhart-Harris; Philip R. Corlett; David Dupuis; Adam L. Halberstadt; Michael Kometer; Eva Kozakova; Frank LarØi; Tehseen N. Noorani; Katrin H. Preller; Flavie Waters; Yuliya Zaytseva; Renaud Jardri


Schizophr Bull. 2020;46(6):1396-1408. 

In This Article


Both in relation to psychedelic use and SCZs pathology, anthropological studies reveal enormous cultural variation that would benefit from a more systematic study. Comparative anthropological studies show that some features of the experiences induced by hallucinogenic plants and mushrooms are similar across cultures (eg, geometric VH), while others vary extensively cross-culturally (eg, subjective feeling tone, meaning, or content of the hallucinations).[96–98] Hallucinogenic substances such as serotonergic plants and mushrooms have been traditionally employed in a variety of sociocultural purposes. For example, species of Anadenanthera and Virola, psilocybin mushrooms, and peyote have been used for divinatory and healing purposes.[99–106] Some of these plants have also been employed in initiation rituals.[107,108] It is worth highlighting that these hallucinogens have also traditionally been used for "non-ritualistic" purposes, for instance, in warfare[109,110] and hunting.[111] Finally, as illustrated by the case of "psilocybin mushrooms parties" held in Mexico, the pre-Columbian recreational use of these plants has been documented.[112]

Observing homogeneity in the features of the hallucinations produced by psychedelics within the same culture, many ethnographers have defended a culturalist approach to psychedelic hallucinations.[97,107,113–117] For instance, terms such as "culturally influenced visions"[117] or "stereotypic visions"[97] have been used to argue that cultural variables are significant in shaping the hallucinogenic experience. Several candidates have been proposed to shed light on the vectors of this enculturation of the hallucinatory content: mythological and cosmological knowledge,[118] kinship system and gender,[118] iconographic representations,[117] verbal exchanges and ritual interactions.[119,120] However, these factors, the underpinnings of their effectiveness, and the sensitivity of different psychedelic substances to their effects require further study.

In the laboratory context, there have been few attempts to identify and experimentally manipulate nondrug variables in studies of serotonergic psychedelics (see Refs.[121,122] for an overview). In one exception, Studerus et al[123] analyzed data from 23 controlled experimental studies, concluding that: the personality trait of absorption ("openness to cognitive, perceptual, imagistic, and other experiences"), the state of mind immediately prior to drug intake and having had few psychological problems in the prior weeks, were most strongly associated with positive experiences, while emotional excitability, young age, and an equipment-heavy experimental setting, were most strongly associated with negative experiences. In the resurgence of clinical therapeutics, extra-pharmacological variables considered especially important for therapeutic outcomes include a safe and supported treatment space, bespoke therapeutic support from trusted guides and appropriate music to accompany psychedelic sessions.[124–126]

There has also been little cross-cultural research on variability in hallucinations in SCZs. Nuevo et al[127] conducted a cross-country study of prevalence of hallucinations finding high variability (eg, from 0.8% in Vietnam to 31.4% in Nepal), but did not analyze this further in order to uncover any potential cross-cultural patterns or correlations between specific cultural factors and the phenomenology of hallucinations. Luhrmann et al[128] compared AH in SCZs patients in the United States, India, and Ghana, arguing that the negative content of AH varied according to culture. However, this was a qualitative, interview-based study, with small numbers, and groups were not compared or matched in terms of co-attendant clinical variables. A large number of questions remain unanswered in terms of what role culture may play in shaping hallucinations (for more detail, see Ref.[129]). The relationship between hallucinations and culture in SCZs and in the use of psychedelics, and the possible overlap between these two research areas merits further study, not least because techniques traditionally mobilized to shape the phenomenology of psychedelic hallucinations in native societies in the Americas may enrich the therapeutic engagement with hallucinations in non-native contexts.[130] This could be especially useful in cases where hallucinations respond minimally to antipsychotic medication.