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The Psychoactive Effects of Cannabis

Even though cannabis has been periodically cultivated in Europe for various purposes—such as for rope, cloth and oil—for several millennia, interest in the psychoactive effects first properly developed in the West almost simultaneously, within a few decades, in France, Britain and the USA in the mid-19th century (Jay 2011:73–104). Early Western researchers occasionally observed that although someone under the influence may seem passive and as though asleep, their mind may nevertheless be racing with a thousand fantasies, dreaming but without sleeping, “un véritable état de rêve, mais de rêve sans sommeil!” (Moreau de Tours 1845:37).

The general effects of cannabis

Numerous studies of the effects of cannabis have been published since the mid-19th century. One of the most comprehensive of the modern era is the seminal study by Tart (1971); more recently, amongst many other publications, further pertinent observations and research on the effects are provided by Abel et al. (1973), Earlywine (2002:67–119; 2005) and Curran and Morgan (2016).

These days the general effects of cannabis are, of course, generally well known.

Familiar, common effects include less vivid dreams, an increase in appetite and thirst, hilarity, contentment, diminished short-term memory, enhanced imagination, slower reaction times to external stimuli, and occasionally difficulties—or probably just reluctance—in sustaining focus on a particular task.

It is well known that cannabis has a mildly ‘psychedelic’ effect, with the consequence that the prevailing mood, inclination and disposition of the consumer are generally exaggerated or enhanced. Someone who feels psychotic, paranoid, sleepy or disinclined to work may experience an enhancement of those feelings. On the other hand, a landscape, a creative task, sex, a film or music (particularly) may become totally absorbing. Moreau de Tours (1845:71–92) devotes a large section of his book to his experiences of music. Sensations of taste, smell, sound and touch are usually heightened. Intimacy with the natural environment may be profound. Being non-toxic, even in massive doses, cannabis is eminently enjoyable as an inebriant.

The issue of psychotic reactions to cannabis has been extensively explored (see, for example, Kaplan 1973; Curran et al. 2016; Morrison et al. 2016); the issue has again been more recently addressed by Di Forti et al. (2019). This latter study indicates that it is high-concentration THC cannabis—some strains possess virtually no CBDs at all (Lee 2012:364)—which tends to induce psychotic reactions in some people, more so than weaker varieties. Strains of cannabis with adequate CBDs, which can counteract the THCs (see the blog ‘Cannabis chemistry’), do not seem to be implicated in psychotic reactions to anything like the same degree.

High doses and hallucinations

Most cannabis users, especially novices or those who have previously fasted, have occasionally experienced strong psychedelic effects from cannabis; but this is not the norm for average consumers using less than an excessive dose. However, it perhaps goes without saying that people have widely varying sensitivities and reactions to various psychoactive plants and drugs in general, depending on their inherent genetics, current mood, diet, and prevailing psychological temperament.

It is well known that the overall effect of cannabis, in less than ‘heroic doses,’ is usually, as an overall condition, mildly soporific. ‘Heroic doses’ of cannabis, induced through eating a few grammes, usually leaves the consumer ‘pinned to the ground,’ until a deep sleep ensues. High doses may induce all kinds of fantasies and dream-like ‘hallucinations’ prior to sleep.

However, when discussing non-ordinary states of consciousness and ‘hallucinations’ it is important to distinguish between ‘genuine’ hallucinations and what might be called ‘enhanced reality’ experiences. Drugs of the Solanaceae (nightshade) family of plants—which includes henbane, datura, mandrake and belladonna—contain atropine and scopolamine, compounds which can induce proper hallucinations of people or things that are not there at all. In distinction, as reported by Charles Baudelaire (1969 [1860]:221) in the 19th century, and commented on by de Ropp (1957:72), the ‘hallucinations’ produced by hashish are not ‘proper’ hallucinations, rather an enhancement of sensations and perceptions affected by the imagination.

The effects of cannabis on students and professors

In an admittedly small but nevertheless pertinent study of undergraduates at two small universities in the USA, Hogan et al. (1973:109) observed that marijuana users, in comparison with non-users, are more socially skilled, have a broader range of interests, are more adventuresome, and more concerned with the feelings of others; they are also more impulsive and non-conforming. (Though this was a study of college students in the late 1960s.)

Interestingly, in the wide-ranging cannabis debate amongst imams in the Muslim world in the 13th–16th centuries, it was noticed that cannabis use did not seem necessarily to impede the intellectual functions or capabilities of a college professor, even though his general appearance was notably different (Rosenthal 1971:84).

Cannabis as a ‘tool of intimacy’

Perhaps one of the best ways to characterize the overall effects of any psychedelic or entheogenic substance might be to think of it as a potential ‘tool of intimacy,’ providing a greater intimacy with oneself, with another person, one’s general environment or specific features of one’s environment, such as the sound or the visual appearance of something. I would suggest that among the most intimate experiences we can have are ‘mystical’ experiences and sex (see the blogs ‘Cannabis users have better sex’; ‘Cannabis as an aphrodisiac’). However, paradoxically, cannabis can also lead to withdrawal from any kind of interaction or engagement with other people; a withdrawn, inner journey.

General features of mystical experience

In The Varieties of Religious Experience, first published in 1902, William James presented for the first time a definition of mysticism that also took into account substance-based experiences. In this book James (1985:380–382) defines four marks of mystical experience: (1) ineffability, (2) noetic quality (of revelations/hidden truth), (3) transiency, and (4) passivity. Although numerous other definitions of mystical/religious experience have since been published, James’ criteria are still among the most commonly accepted (Dupré 2005:6341). These criteria, I would suggest, apply quite well to experiences that people occasionally have with cannabis in conducive circumstances.

What I have termed ‘associative thinking’ is another hallmark of mystical experience (Clark 2020:77–102) and typical of cannabis inebriation, in varying degrees. Sequential cause-and-effect chains of reasoning may be supplanted by associations between what in sober consciousness may not appear to be particularly related. At the extreme, but relatively rarely, synaesthesia may ensue. Associative thinking can lead to enhanced creativity, particularly in music.

Cannabis and mystical experience

There are, of course, widely different depths of mystical experience, from light or fleeting associations to trance; and it also needs to be emphasized that many people may use cannabis for a lifetime, but if their personal psychology is not so inclined, may never have any kind of ‘mystical experience’ at all.

The (usually) mildly psychedelic effect of cannabis typically results in a different sense of time, which, particularly from high doses, appears to slow down, sometimes extremely. Some people also report distortions of space. It has been observed by many commentators (for example, Zaehner 1972:7) that the sense of time ‘stopping’ is a common denominator of almost all forms of mysticism. A vital component of mystical experience is that the mind and body become entirely still and meditative.

This ‘stopping’ of activity allows a more focused or heightened degree of perception, such that one may be able to read another’s mental or psychological state more clearly than when sober; one may have a sense of one’s ‘third eye’ being open and seeing ‘behind the veil,’ perhaps perceiving people as actors or characters in a theatre. It could be surmised that it was this kind of experience of ‘spiritual insight’ that led to the reverence for cannabis by some religious sects of South Asia, such as by devotees of the god Śiva, some sects of Sūfīs and the Nihangs (a sect of Sikh soldiers) of the Punjab.


Regarding the effects of cannabis on society in general, it could be argued that  psychological and environmental problems arising from a partial divorce—or  ‘distancing’—from other people and nature can only be successfully addressed through a deeper sense of intimacy with ourselves, others and our environment. Learning to become generally more intimate through various kinds of experiences might perhaps be a viable way for practically addressing some of the problems of humanity.


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Cultivation information, and media is given for those of our clients who live in countries where cannabis cultivation is decriminalised or legal, or to those that operate within a licensed model. We encourage all readers to be aware of their local laws and to ensure they do not break them.

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Matthew Clark

Since 2004, Dr. Matthew Clark has been a Research Associate at the School of Oriental and African Studies (University of London), where he taught courses on Hinduism between 1999 and 2004. He has spent many years in India, which he first visited in 1977, visiting nearly all important (several hundred) pilgrimage sites and trekking around 2,000 miles in the Himalayas. He first engaged with yoga in the mid-1970s and began regularly practicing Ashtanga Yoga in 1990. Since 2006 has been lecturing worldwide on yoga, philosophy, and psychedelics. He is one of the editors of the Journal of Yoga Studies and is one of the administrators of the SOAS Centre of Yoga Studies. His publications include The Daśanāmī-Saṃnyāsīs: The Integration of Ascetic Lineages into an Order (2006), which is a study of a sect of sādhus; an exploration of the use of psychedelic plant concoctions in ancient Asia and Greece, The Tawny One: Soma, Haoma, and Ayahuasca (2017); and a short book on yoga, The Origins and Practices of Yoga: A Weeny Introduction (revised edition) (2018).