The potential of psychedelic drugs in the treatment of mental health problems is increasingly being recognized. However, relatively little thrust has been given to the suggestion that individuals without any mental health problems may benefit from using psychedelic drugs, and that they may have a right to do so. This review considers contemporary research into the use of psychedelic drugs in healthy individuals, including neurobiological and subjective effects. In line with findings suggesting positive effects in the treatment of mental health problems, such research highlights the potential of psychedelic drugs for the enhancement of wellbeing even in healthy individuals. The relatively low risk associated with usage does not appear to align with stringent drug laws that impose heavy penalties for their use. Some policy implications, and suggestions for future research, are considered.

Researchers and clinicians are becoming increasingly open to the possibility that psychedelic drugs might prove useful in the treatment of mental health problems. Studies conducted primarily in the 1950s and 1960s furnished a wealth of (methodologically imperfect) clinical findings to suggest beneficial effects of psychedelic drugs in the treatment of mood, anxiety, and addictive disorders (Grinspoon and Bakalar, 1979; Sessa, 2005). However, due to highly restrictive drug laws that effectively foreclosed research into psychedelic drugs in the 1960s, their possible benefits have been widely overlooked (Nutt et al., 2013). More recent studies have begun to corroborate the suggestion that treatments involving psychedelic drugs may be effective in the alleviation of a range of mental health problems (see Vollenweider and Kometer, 2010 for a review). In light of such findings, several authors have argued for changes in drug policy in order to facilitate basic research and treatment innovation regarding psychedelics (Gross, 2013; Nutt et al., 2013).

However, relatively little thrust has been given to the argument that even healthy individuals can experience considerable benefits from consuming psychedelics, and that they may have a right to experience these (Walsh, 2016). Bioethical discussion of the use of drugs in the healthy population to improve wellbeing has typically focused on the use of pharmaceuticals such as selective serotonin reuptake inhibitors (SSRIs) and other antidepressants as a means of improving mood (Kramer, 1993; Schermer, 2015). Either through the true lack of effects or due to inadequate research designs, evidence for strong mood enhancing effects of such substances in healthy individuals is scarce (Ilieva, 2015; Repantis et al., 2009). Without evidence for clear effects, and with the necessity for relatively long-term, daily usage before any such effects are likely to be apparent (Harmer, 2008), coupled with the possibility of unpleasant side effects further deterring usage, it seems unlikely that a large number of otherwise healthy individuals would seek to use these pharmaceuticals for the purpose of improving their lives. In contrast, over 30 million people in the United States are estimated to have experimented with psychedelic drugs (Krebs and Johansen, 2013a), and with new research garnering considerable attention and suggesting positive effects, it seems possible that more individuals may seek out psychedelic experiences. Use of psychedelic drugs in this way may prompt not only bioethical, but legal discussions. It is essential that such discussions proceed in a way that takes current scientific research into account.

The purpose of this review is to provide an up to date overview of current knowledge regarding psychedelic drug effects in healthy individuals, with the hope of grounding future discussion of psychedelics in the existing evidence base. I first describe the psychedelic state and present research on its neurobiological underpinnings. I then review contemporary research on the effects of psychedelic drugs in healthy individuals. This is followed by consideration of possible adverse effects. Finally, I consider some implications of such research for drug policy.

Psychedelic drugs and the psychedelic state Psychedelics are a type of drug capable of reliably bringing about states of altered perception, thought, and feeling that are not usually experienced, besides in dreams or during religious exaltation (Jaffe, 1990), and have been used for their mind-altering properties for thousands of years (Bruhn et al., 2002; Schultes and Hofmann, 1979; Strassman, 1984). Classic psychedelics include dimethyltryptamine (DMT—found in ayahuasca), lysergic acid diethylamide (LSD), mescaline (found in peyote), and psilocybin (found in “magic mushrooms”). Psychedelic researchers have delineated three broad stages of psychedelic drug effects (Majić et al., 2015). Firstly, shortly after drug administration, a short-term (lasting from minutes to hours) acute psychedelic state is induced. This phase is characterized by a significant alteration of conscious experience, and in some cases may result in a ‘complete mystical experience’, also known as a psychedelic peak experience (Majić et al., 2015). Complete mystical experiences include a sense of unity (e.g. merging with the universe, the sense that all things are one), ineffability (being unable to fully describe the experience in words), a deep positive mood, a sense of sacredness or awe, transcendence of time and space, and a noetic quality (a feeling of revelation or intuitive understanding) (Pahnke, 1969). Secondly, it has been reported that following the acute drug phase, a ‘psychedelic afterglow’ state may be produced, in which the recipient of the drug may have an elevated mood and feel less burdened by previous worries (Pahnke, 1969). This phase typically subsides after approximately 2–4 weeks (Majić et al., 2015; Pahnke, 1969). Finally, as discussed in more detail below, over the long term there may be lasting psychological changes precipitated either by general drug effects or the subjective psychedelic/mystical experience itself.

Drug policy and psychedelic use in the healthy population In several cases in different countries, exemptions have been made for the use of psychedelics as part of religious practices. While precise exemptions differ by state, use of peyote by the Native American Church is legal in the United States. Other uses of psychedelics have become more of a global issue for lawmakers. Religious groups such as the Santo Daime and União de Vegetal, which frequently incorporate ayahuasca into their spiritual practices, have expanded outside of their native country of Brazil, prompting assessments of the rights of individuals to use psychedelic drugs in religious contexts even in countries where there is no longstanding tradition of use (Labate and Feeney, 2012). When considering the use of ayahuasca in religious ceremonies, the United States Supreme Court has ruled that drug laws may be trumped by freedom to practice religion, in accordance with the Religious Freedom Restoration Act of 1993 (Tupper, 2008). The Netherlands has also granted the right to use ayahuasca in religious and spiritual ceremonies to the Santo Daime, owing to insufficient evidence that the brew causes any harm (Adelaars, 2001). However, other countries have not always granted freedom of use. The fact that ayahuasca contains DMT was enough to suggest a public health risk that was deemed to outweigh religious freedom in Germany (Labate and Feeney, 2012; Rohde and Sander, 2011). Exemptions for religious purposes raise questions regarding appropriate definitions of religion, and there have been concerns over whether religious pretensions might merely be used to cloak the otherwise illegal consumption of psychedelic substances (Sandberg, 2011). More libertarian commentators, however, have argued that such considerations may be beside the point. Religious and therapeutic exemptions are seen to perpetuate the notion that the state has a right to determine appropriate uses of substances even when no evidence can be furnished that their use impinges on the rights or wellbeing of individuals in wider society (Walsh, 2016). Walsh (2016) proposes that, instead of pursuing specific exemptions for psychedelic drugs in religious and therapeutic contexts, a broader exemption can be made for the use of psychedelics on the grounds of cognitive liberty. Prohibitions on psychedelic drugs may be seen to amount to prohibitions on the right to control one’s own mind and conscious experience, precluding access to volitionally chosen but otherwise inaccessible drug states (Boire, 2001; Roberts, 1997). Given that considerations of religious legitimacy typically make distinctions between ‘merely’ philosophical perspectives and religious views, even securing the right to consume psychedelics in religious practices means that the potentially life enhancing experiences and insights that might be gained through their use is essentially off limits (without risk of legal repercussions) to those who do not hold mystical beliefs. Walsh (2010) notes that article 9 of the European Convention on Human Rights enshrines not only the right to religious freedom, but also freedom of thought. If freedom of thought is to mean anything, it is argued, it must surely incorporate freedom to direct one’s own mental states to the extent that this is possible (Boire, 2001; Roberts, 1997; Walsh, 2016). The use of psychedelic drugs only for the purpose of treatment has also been a subject of debate. The distinction between treatment and enhancement, or between therapeutic and recreational uses, is not immediately clear. Making a binary distinction between treatment, which would be argued to be the remediation of some specific pathology, and enhancement—the improvement of a function or capacity deemed normal—begs several questions. Firstly, a clear definition of pathology would be needed to justify an intervention. This is particularly troublesome where mental health is concerned, because pathology is most frequently inferred based on the presence of symptoms that are not specific to any one disorder, which are present to varying degrees in the general population, and for which the underlying causes (i.e. pathology) are largely unknown. Secondly, it assumes that normality is synonymous with good health and wellbeing, and that this is merely the lack of (ill-defined) disease constructs. To the contrary, many authors argue that conceptions of health and wellbeing ought to encompass not only the absence of clear pathology, but also the potential of humans to develop and realize their full potential (Labate and Cavnar, 2013; Walsh, 2016). Current research on the use of psychedelics suggests that these drugs may allow otherwise healthy individuals to improve themselves and increase their wellbeing, with no apparent cost—and possibly benefits—to those around them. A distinction between the use of psychedelics for clear cases of treatment versus enhancement may still make sense in healthcare settings, where service providers must make judgments as to the most pressing cases, and where public funds may be used to support interventions. It seems reasonable to suggest that treatments for severe mental health problems should be prioritized over less pressing desires for improvements in wellbeing in healthcare settings. From a legal perspective, however, the nebulous boundary between treatment and enhancement, and indeed between religious and personal discovery or spiritual uses, raises problems for the clarity of law. For example, is a person who has used a psychedelic to try and gain insight into their non-clinical levels of anxiety considered to be self-medicating, or enhancing their self? Is this use to be considered wrong purely by virtue of being outside of a healthcare setting and therefore illegal? Moreover, the distinction between treatment and enhancement does not track any meaningful change in the cost to society that the law is aimed at protecting, nor benefits that might be gleaned by the individuals that make up society. Unfortunately, some policy developments may be proceeding without due consideration of different drugs and their effects. The recent enactment of the Psychoactive Substances Act in May 2016 in the UK, which aims to prohibit psychoactive substances, not only ignores consideration of benefits people might derive from a psychoactive substance, but even sidesteps the need to demonstrate potential for harm. It is notable that this act seems to have been made to curb the proliferation of ‘new psychoactive substances’ (NPSs), also known as ‘legal highs’, whose presence in the market is the direct result of bans on existing psychoactive substances that are known to pose little danger, notably typical psychedelics LSD and magic mushrooms (DMT) (Gross, 2013). If a rational drug policy were pursued regarding existing psychoactive substances, then there would be less impetus for the development of new ones, the risk profiles and purity of which are unknown. Despite evidence indicating that psychedelic drugs pose little threat to the individual user or cost to society and may have substantial benefits, LSD, DMT, and psilocybin remain among the most strictly prohibited substances in the UK, USA, and elsewhere (Nutt et al., 2007). Of course, it may be argued that regardless of actual drug laws, psychedelics are relatively easy to procure illegally. Nevertheless, risk to those consuming psychedelics obtained illegally is likely to be higher than where use is legalized. For example, beyond potential legal ramifications, there are no checks on the purity of illicitly obtained drugs. Furthermore, ‘copycat’ substances are sometimes produced to avoid trouble with the law, and the risk profile of these may differ markedly from known psychedelics. Beyond personal use of psychedelics in healthy subjects, current drug laws stifle the use of psychedelics for research purposes in healthy individuals. Very few research labs currently have permission to investigate psychedelics, and permissions typically impose standards that are very difficult and costly to meet (Nutt et al., 2013). Research in healthy subjects will prove highly informative in understanding the nature of the psychedelic state and drug mechanisms, which may ultimately help in understanding how these drugs can best be utilized therapeutically. Several suggestions have been made regarding how policy regarding psychedelics might be made more reasonable. Nutt et al. (2007) have strongly urged that drug classification should correspond to what empirical investigation actually shows to be the relative harms of different drugs. Classification also tends to consider possible benefits of usage for medical purposes. As we have discussed above, there are significant benefits that might be gained from the use of psychedelics outside of strictly medical settings, and these might also be considered when rating drugs. Some public health experts have suggested other ways that a more reasonable stance towards psychedelics might be taken, based on models of treatment administration or use in religious contexts. For example, Haden et al. (2016) have suggested that psychedelics could be administered in controlled settings to healthy individuals provided that trained individuals oversee it. Certifications advancing in their rigor and the usage of psychedelics that they allow (e.g. whether one can offer psychedelic psychotherapy, or charge for one’s services) could be earned that provide supervisors with the knowledge and skills to safely administer psychedelic drugs to healthy individuals. Production, purity, and sale of the drugs could be monitored and controlled, and tax revenue could be increased, as well as increasing safety of usage by training in set and setting. Whatever specific course of action is taken with regards to drug policy, consideration of evidence regarding risks and benefits can only improve policy.

Conclusion Many drug researchers have urged the reclassification of psychedelic drugs so that their therapeutic potential can be fully realized (Nutt et al., 2013). From current results, it would seem that it is not only those with psychological impairments who might stand to gain from the use of psychedelics. When used appropriately, psychedelic drugs have been shown to have positive effects among healthy individuals, with single doses capable of producing lasting changes in wellbeing and purpose. A rational drug policy derived from empirical research into the potential costs and benefits of different drugs may not only facilitate the treatment of mental disorders, but the safe and enriching use of psychedelic drugs more generally.

Declaration of conflicting interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding The author(s) received no financial support for the research, authorship, and/or publication of this article.