Ayahuasca is a South American psychoactive beverage, traditionally used by Indigenous cultures and folk healers in the Amazon and Orinoco basins for spiritual ceremonies, divination, and healing a variety of psychosomatic complaints.
Originally restricted to areas of Peru, Brazil, Colombia and Ecuador, in the middle of the 20th century it became widespread in Brazil in the context of the appearance of syncretic religions that use ayahuasca as a sacrament, like Santo Daime, União do Vegetal and Barquinha, which blend elements of Amazonian Shamanism, Christianity, Kardecist Spiritism, and African-Brazilian religions such as Umbanda, Candomblé and Tambor de Mina, later expanding to several countries across all continents, notably the United States and Western Europe, and, more incipiently, in Eastern Europe, South Africa, Australia, and Japan.
More recently, new phenomena regarding ayahuasca use have evolved and moved to urban centers in North America and Europe, with the emergence of neoshamanic hybrid rituals and spiritual and recreational drug tourism. Also, anecdotal evidence, studies conducted among ayahuasca consumers and clinical trials suggest that ayahuasca has therapeutic potential, especially for the treatment of substance dependence, anxiety, and mood disorders. Thus, currently, despite continuing to be used in a traditional way, ayahuasca is also consumed recreationally worldwide, and is considered as a potential future treatment in modern medicine. Ayahuasca often causes nausea and vomiting and has a number of rarer more serious possible side effects including breathing difficulties and seizure; it may cause psychosis in those predisposed to the condition.
Ayahuasca is a hallucinogen commonly made by the prolonged decoction of the stems of the Banisteriopsis caapi vine and the leaves of the Psychotria viridis shrub, although hundreds of species are used in addition or substitution (See "Preparation" below). P. viridis contains N,N-Dimethyltryptamine (DMT), a highly psychedelic substance. Although orally inactive, B. caapi is rich with harmala alkaloids, such as harmine, harmaline and tetrahydroharmine (THH), which can act as monoamine oxidase inhibitors (MAOi). This halts the liver and gastrointestinal metabolism of DMT, allowing it to reach the systemic circulation and the brain, where it activates 5-HT1A/2A/2C receptors in frontal and paralimbic areas.