So there are really two questions here. "Did the Buddha and early Buddhists use drugs?" and "Have Buddhists used plants as drugs?" Before we dig into these I think we need some background on two other things, those being the history of entheogens in India and American Psychedelic culture.

First off, lets talk the Vedas. The Ṛgveda began composition conservatively around the 15th century BCE (Or -10th Century BE, if you prefer), about the time or shortly after the Indo-Aryans split from the Indo-Iranians. It continued to be composed until around the 9th or 10th century BCE with maybe a few hymns composed slightly later. Soma first appears in the 8th book or maṇḍala (Sanskrit: Circle) of the Ṛgveda which is thought to have been composed towards the end of this period. Of course, all of this is a little misleading. Saying that it was written or composed implies a uniformity that isn't exactly there. Rather than seeing the Ṛgveda as a cohesive whole, it is better to see it as an organization of the hymns and practices of the Vedic peoples over time, compiled into a work for memorization. So, the hymns from a later period don't necessarily represent a later tradition, nor does this mean that that they are themselves younger.

The point of all this is that Soma appears in a later script, but it has clear parallels with the Old Iranian religion, and its descendant Zoroastrianism in the form of their sacred drink, Haoma, which is the Avestan form of the Sanskrit Soma. This means that the practice was presumably part of Indo-Iranian religion meaning that the plant must have been found in Central Asia rather than India. Based on this, numerous identities for the plant have been put forward, most assuming it to be a psychedelic entheogen, from psychedelic mushrooms (psilocybin and amanita) to forms of hemp and marajuana, however all have missed the mark. Furthermore, the very assumption that it was a psychedelic could be wrong. The assumption that it was used by shamanic priests to trigger a hallucinogenic trance was widely assumed, but not necessarily correct. The idea that it was a hallucinogen gained traction in the 50's and 60's during the psychedelic boom but soon fell out of favor and scholars have drifted towards an earlier proposal, that it was a stimulant made from ephedra. Ephadra has mild to strong stimulant properties and has commonly been used as a medicine for a very long time, it is often ground to a paste or made into a tea and consumed for it's benefits. Today, it is used as the Haoma of many Parsīs.

However, Wendy Doniger has pointed out that the initial plant is not necessarily the end of the argument. Soma has changed over time, the the question becomes, was Soma in India ever a hallucinogen? The answer to this is even more complicated, but I think it is both impossible to prove or rule out entirely. Soma was mythologized over time and Brāhmaṇas used "substitutes" in their rituals or sought other plants. However, I think it would be without controversy to say that Soma, whether psychoactive or not, had fallen out of usage by the time of the Buddha.

Second we have to talk about the psychedelic revolution of the late 50's through the 60's. The discovery of LSD in 1943 and its public release in '47 began a small subculture that explored the effects. In 1953, Philosopher, Writer, and Romantic Transcendentalist Aldous Huxley released his book The Doors of Perception detailing his experiences with mescaline and other psychedelics. Around the same time, the psychedelic mushrooms and plants such as peyote and salvia moved from curiosities in the academic community and into popular culture. The Beat Generation began a sort of psychedelic awakening with Jack Kerouac, Allen Ginsberg, and William S. Buroughs advocating the use of psychedelics and marijuana for spiritual and creative reasons. In 1962, Harvard Professors Timothy Leary and Richard Alpert began the Harvard Psychedelics Experiments and and became heavy users themselves. After being fired for their conduct they became advocates for psychedelics and their use to achieve "higher states of consciousness" publishing The Psychedelic Experience in 1964. By the mid 60's, psychedelic culture exploded led by bands like the Beatles, the Who, and the Rolling Stones with more psychedelic bands soon following like the Jimi Hendrix Experience and Cream. Timothy Leary and others remained at the front of this movement while the old school transcendentalists and beat poets fell by the wayside, casualties of the hippy movement and revolution, though always remaining on the edge.

What does this have to do with Buddhism, you might ask? Everything. Huxley and the Transcendentalists were fascinated by Eastern Religions, though they tended to conflate them. Huxley and his were inspired by Vendānta and were early champions of it in America, others drifted towards Taoism, though all recognized Buddhism as a sort of kin to them. Ginsberg and the Beat Poets drifted towards DT Suzuki's Zen and the aesthetic theory of it, utilizing Zen influences in their poetry. They later moved towards Tibetan under the influence of notable teacher Chogyam Trungpa and Ginsberg helped found the first Buddhist University in America, Naropa. The Psychedelic movement as a whole became tangled up with Eastern mysticism as Hinduism made its way to America and Europe through Gurus and Cultural Icons alike. Buddhism was of course included in this, though seen as basically Hinduism, sadly misunderstood or utilized only aesthetically. And that fateful book, The Psychedelic Experience? It was an interpretation of the book popularly known as The Tibetan Book of the Dead through the lens of ego death and psychedelia.

Thus in the American conscious, Buddhism became about higher states of mind. Nivana a sort of ego death or altered state, indistinguishable from the sort found in things like LSD. Perhaps this is what the Buddha was advocating?

Of course, such a thing is quite wrong.

In the Buddha's day, psychoactive drugs were quite limited. Soma, as we have mentioned, had fallen out of use for the most part and the main way of triggering hallucinogenic experience was meditation or extreme asceticism. However, alcohol remained popular, very much so. Wines, Beers, and Mead are well attested in the Vedic texts as well as secular ones. The Buddha and his Śramaṇa contemporaries, like Mahāvīra, went against the grain and forbid the use of fermented drinks and alcohol, as well as any mind altering substance. Indeed the Fifth Precept of Buddhism is to not take them. The Buddha said this apparently because intoxication is detrimental to the Buddhist path, because it prevents mindfulness and causes people to behave harmfully and irrationally. While the Buddha did not have a stance on psychedelics, other Buddhists have and they strongly recommend against it.

However, that is not the full story. Traditions change over time and Buddhism is no exception. Enter Tantric Buddhism and the Vajrayāna.

During the Pala Dynasty, or perhaps slightly before. A movement called Tantra started in India. The Tantras were esoteric elaborations of earlier movements especially Buddhism and Śaivism. While now known in the west mainly for its sexual component and understood through an orientalist lens, the Tantra is a diverse tradition full of a number of distinct types of practice, ranging from mantras, to yoga, to complex mandalas, to visualization practices, to, yes, sex. This movement dramatically shifted the paradigm of Indian religions, taking the focus away from the Brahmāṇas and the Monastics to wandering Siddha saints. Of course, neither disappeared and both absorbed the practices of these Siddhas.

One of the key innovations in Tantra was the revival of entheogens. Buddhism and the Buddhist Tantras utilized Cannabis and Datura as an aid on their quest to spiritual perfection and in order to facilitate deity visualization and deepen the spiritual experience. The Crazy Wisdom of meditation masters, skilled in the tantra was used to shock and also facilitate greater spiritual awakening. When Buddhism entered Tibet, it entered with these practices, some of which have continued to this day. We are kind of out of my wheelhouse here perhaps u/jimedorje can explain more though.

In any case, it's wrong to say that the Buddha advocated drug use, but we also cannot say that Buddhists never have. Even today modern Buddhist teachers with legitimate lineage will sometimes advocate their potential (though typically with reservations) or note that they have been used. Similarly, practices continue in esoteric Buddhism which utilized methods of triggering psychedelic or hallucinogenic experiences in practitioners.

References and Further Reading

• AK Warder. Indian Buddhism 3rd Ed. 2000.

• Allen Hunt Bardiner Zig Zag Zen: Buddhism and Psychedelics 2002. Chronicle Books.

• Bhikkhu Bodhi. The Connected Discourses of the Buddha. 2000. Wisdom Publications

• The Numerical Discourses of the Buddha. 2012. Wisdom Publications

• The Buddha's Teachings on Social and Communal Harmony. 2016. Wisdom Publications.

• Bhikkhu Bodhi and Ñāṇamoli Bhikkhu The Middle Length Discourses of the Buddha. 1995. Wisdom Publications.

• Jan E. Houben The Soma-Haoma Problem Electronic Journal of Vedic Studies volume 9. Issue 1a.

• Jesse Jarnow Heads: a Biography of Psychedelic America. 2016. Da Capo Press.

• Richard Gombrich. Therevāda Buddhism: a Social history from ancient Benares to Modern Colombo 2nd Ed. 2006. Routledge.

• Richard Robinson, Willard Johnson, and Ṭhānissaro Bhikkhu The Buddhist Religion: A Historical Introduction 4th Edition. 1997.

• Ronald Davidson Indian Esoteric Buddhism 2002. Columbia University Press.

• Ṭhānissaro Bhikkhu Buddhist Romanticism 2018.