Psychedelics, and particularly classic psychedelics, encompass a class of serotonin 2A receptor (5-HT2AR) agonists that can produce changes in consciousness. These substances can affect cognitions, perceptions, emotions, and sense of self (Aday et al., 2020, 2021). They can also occasion mystical experiences (Barrett et al., 2015; Carhart-Harris et al., 2016; Griffiths et al., 2006, 2008, 2016), characterized by feelings of meaning/sacredness, interconnectedness, transcendence of time and space, ineffability, and positive mood (Aday et al., 2020). People sometimes turn to these substances for spiritual reasons (Popovici & Simion, 2017), and many people interpret psychedelic experiences through a spiritual lens (Exline et al., 2023; Baumeister & Placidi, 1983). Although using psychedelics recreationally is illegal in most parts of the U. S., controlled clinical studies have shown that psychedelics have the power to reduce symptoms of depression (Carhart-Harris et al., 2016; Griffiths et al., 2016), addiction (Bogenschutz & Johnson, 2016; Garcia-Romeu et al., 2014), obsessive–compulsive disorder (Moreno et al., 2006), death anxiety (Griffiths et al., 2016; Ross et al., 2016), and post-traumatic stress (Krediet et al., 2020). We were interested in a complementary question: Might psychedelics have the potential to facilitate perceptions of spiritual growth? We reviewed prior studies that addressed this question.

What are psychedelics?

Broadly speaking, psychedelics—sometimes called hallucinogens or entheogens (i.e., “generating the god within”; Ruck et al., 1979)—include substances such as psilocybin (“magic mushrooms”), lysergic acid diethylamide (LSD; “acid”), N,N-dimethyltryptamine (DMT), ayahuasca, mescaline, ketamine, and methylenedioxy-methylamphetamine (MDMA; “ecstasy”). Psychedelic effects vary and can be unpredictable (for a review, see Aday et al., 2021). The effects of psychedelics may include distortion, enhancement, or amplification of human perceptions, cognitions, and emotions (Preller & Vollenweider, 2018). Scientific interest in psychedelics exploded in the 1950s and 1960s, and early researchers recognized their therapeutic potential (Pollan, 2018). However, psychedelics are also laced with controversy; psychedelic research was largely suspended in the 1970s due to tightening pharmaceutical regulations and increasing social pressure to restrict research (Oram, 2016; Strassman, 1991).

Although Nichols (2016) suggested that psychedelics are physiologically safe and not physically addictive, psychedelic use carries important risks, including impaired judgment (Nichols, 2016), “bad trips” (intense, frightening experiences; Barrett et al., 2016; Carbonaro et al., 2016, Johnstad, 2021), persisting changes in perception or mood (e.g., Hallucinogen Persisting Perception Disorder; Halpern et al., 2018), adverse neurological side effects (see Parrott, 2014a, b), and legal problems in areas where the substances are illegal (Pilecki et al., 2021). Psychedelic use may carry religious and spiritual risks, as well, including spiritual struggles (Citations removed for masked peer review). Evidence regarding the relationship between psychedelic use and psychopathology is mixed, but there is enough concern for psychedelics to encompass their own class of substance-related disorders in the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; American Psychiatric Association, 2013). Psychedelics can worsen existing mental health conditions, and some studies found weak associations between psychedelic use and psychosis (Lebedev et al., 2021; Nutting et al., 2021).

Because of these risks and controversies, psychedelic science remained mostly dormant until the 1990s. However, psychedelic research has recently seen a substantial resurgence (Apud, 2016). This recent wave of research has largely focused on the promising clinical applications of psychedelic substances in controlled settings, with an emphasis on the mechanisms underlying psychedelic effects (Mitchell & Anderson, 2024).

Psychedelics, spirituality, and psychology

Links between psychedelics and spirituality continue to have major implications for the field of psychology. Historically, these connections influenced the transpersonal paradigm, which focuses on integrating spiritual phenomena to serve individual and societal development (Ferrer, 2014). Spiritual experiences also played an important role in shaping scientific ideas for researchers interested in the therapeutic potential of psychedelics (Apud, 2016). Psychedelics can produce potent subjective experiences, which may play a role in the clinical effectiveness of these substances (Yaden & Griffiths, 2021). As early as 1967, Hoffer and Osmond found that alcoholic patients who received large doses of LSD and had mystical or meaningful experiences showed the greatest improvement in their substance use treatment outcomes (Apud, 2016). Although some consider mystical experiences to be crucial to the therapeutic use of psychedelics (Yaden & Griffiths, 2021), there is some contention around this point (e.g., Olson, 2020). In two separate studies, Ross et al. (2016) and Griffiths et al. (2016) found that the more mystical one’s psilocybin session was rated, the greater the reductions in depression six months after the session. Other researchers found that the degree to which one had a spiritual and unitive experience while using psychedelics predicted reductions in depression (Aday et al., 2020).

Spiritual growth

The purpose of this systematic review is to summarize previous findings on psychedelic use and indicators of spiritual growth. Spiritual growth involves positive transformations in a person’s larger sense of purpose and their relationship with whatever they perceive as sacred (Pargament & Exline, 2022). Spiritual growth can also be thought of as a deepening of the dimension of a person that is concerned with ultimate ends and values (Tu, 2006). It is typically framed as a long-term subjective effect (vs. more immediate mystical or spiritual experiences).

People can perceive spiritual growth in many ways. For example, some might see themselves as drawing closer to divine entities through reading scripture; others could feel an increased sense of meaning by adhering to religious and spiritual (r/s) values or rules, and still others may experience a sense of awe or self-transcendence through practices like meditation. Researchers have used a variety of indicators to study perceptions of spiritual growth (see Table 1 below), including increased r/s faith, increased engagement with r/s practices, increased spiritual well-being, self-transcendence, closeness with divine entities, positive changes in worldview, and more. Although these indicators can be challenging to quantify, several instruments have been created to measure aspects of spiritual growth. For example, the Spiritual Transformation Scale (Cole et al., 2008) assesses spiritual growth across four domains (worldview, goals/priorities, sense of self, and relationships). Because growth is a broad concept and there are many ways to conceptualize spiritual growth (Pargament & Exline, 2022; Piedmont, 1999), we considered a wide range of growth indicators for this review. These indicators were condensed and categorized in Table 1.

Table 1 Subjective indicators of long-term spiritual growth
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Hypotheses

Many people have psychedelic experiences that they frame as spiritual or mystical (e.g., Barrett et al., 2015; Yaden et al., 2017), and psychedelic use can lead to lasting positive changes in a variety of mental health conditions (Luoma et al., 2020). In a parallel fashion, we expected that changes in spirituality related to psychedelic use have the potential to last beyond the brief timeframe of the psychedelic experience itself, creating longer-term changes that could include spiritual growth (or at least perceptions of growth). For example, psychedelic experiences might prompt individuals to contemplate or re-evaluate r/s ideas. Psychedelics could also give rise to revelations about the divine, the self, and the human condition, leading to enduring changes in one's philosophical or spiritual beliefs. Additionally, psychedelics may evoke strong feelings of empathy, compassion, and awe, inspiring a deeper appreciation for the mysteries of existence and encouraging individuals to be more altruistic. Such changes could persist long after the psychedelic experience is over. Thus, we expected to find links between psychedelic use and the spiritual growth indicators outlined in Table 1.

Method

We conducted a literature search using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) review methodology (Page et al., 2021). We included only studies that: (a) were empirical, (b) included use of at least one psychedelic substance, and (c) evaluated at least one of the spiritual growth indicators from Table 1. We included studies focusing on both recreational and clinical use. We reviewed the literature in two phases: a first search focused on work published before June 13, 2022; phase two went to September 18, 2023.

During each phase, two steps were used. First, we searched keywords using PubMed and EBSCOhost Research Platform, which were filtered for peer-reviewed journal articles. EBSCOhost allows access to a range of databases, including APA PsycArticles, APA PsycBooks, Psychology and Behavioral Sciences Collection, AHFS Consumer Medication Information, CINAHL Complete, eBook Collection, Education Source, GreenFILE, Health Source: Nursing/Academic Edition, Library, Information Science & Technology Abstracts, MEDLINE, SocINDEX with Full Text, and ERIC. We paired keywords “psychedelics” and “entheogens” with: “spiritual growth,” “spiritual experiences,” “religious experiences,” “spiritual struggles,” “religious struggles,” “religious coping,” “coping,” and “spirituality,” for a total of 16 search combinations. There were no restrictions based on publication date, language, or sample size. The first search yielded 114 potentially relevant articles, and the second yielded 41. The first author screened each article.

Second, we searched the reference lists of each article to find additional studies. After screening the studies, we eliminated 88 articles in the first phase and 32 in the second. Table 3 in Appendix 1 shows examples of excluded studies and their reasons for exclusion. Most studies were excluded because they were irrelevant, measured immediate spiritual experiences vs. perceptions of longer-term spiritual growth, did not measure any indicators of spiritual growth, were not empirical (e.g., literature reviews), or used insufficiently rigorous methodology.

In phase one, 25 papers (24 independent samples) met inclusion criteria. In phase two, nine papers (eight independent samples) met criteria. The final review included 34 studies (32 independent samples). We then grouped studies according to each indicator of spiritual growth. When coding the studies, we included the citation, sample size, demographics, type(s) of psychedelics used, publication status, research design, measures of psychedelic experiences, measures of spirituality, indicator of spiritual growth, and general findings.

Results

Results are organized into two subsections. The first subsection discusses the methodology of the studies. The second subsection reviews empirical findings related to spiritual growth and is organized by specific indicators of spiritual growth.

Review of methodology

The 25 studies from Phase 1 included a total of 11,940 participants, and the nine studies from Phase 2 included 7,784 participants (total n = 19,724). See Table 4 in Appendix 1 for detailed information about sample demographics, including gender, median age, r/s orientation, and race/ethnicity. Table 5 in Appendix 1 includes the measures that were used to evaluate psychedelic experiences and religious/spiritual effects in each study. Table 2 (below) presents information about each study’s research design, sample size, the psychedelics that were investigated, indicators of spiritual growth, general findings, study strengths, and study weaknesses. Note that Table 2 is meant to provide a general orientation to the studies. Specific findings related to spiritual growth are detailed in the section labeled “Psychedelics and Indicators of Long-term Spiritual Growth” section immediately following Table 2.

Table 2 Research information for included studies (in Alphabetical Order)
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Psychedelics and indicators of long-term spiritual growth

We interpreted increases in indicators of spiritual growth from before to after psychedelic use as perceived spiritual growth. Additionally, we included cross-sectional studies that asked participants about indicators of spiritual growth retrospectively, given they provided sufficient detail. The subsequent sections highlight the most salient findings and are categorized by the indicators outlined in Table 1.

Perceived closeness with the divine

In a large survey (n = 4,285), Griffiths et al. (2019) found that more than two-thirds of those who identified as atheists before encountering God while using psilocybin no longer identified as atheists after the experience. These results resembled those of another large cross-sectional study (Davis et al., 2020, n = 2,561), which showed a shift from 28% atheists and 27% agnostics before DMT use to 10% atheists and 16% agnostics after. Beliefs in ultimate reality or a higher power increased from 36 to 58%. In a third cross-sectional study (n = 800), some U.S. adults indicated a belief that psychedelics could facilitate communication with divine entities when asked about their attitudes toward psychedelics (Exline et al., 2022). A mixed-method study (Kavenská & Simonová, 2015) found that nearly 50% of participants who traveled to the Amazon for an ayahuasca ceremony reported (re)-discovering God or the purpose of life, in addition to overall spiritual development. Finally, Nayak et al. (2023) factor analyzed 45 belief statements from survey respondents (n = 2,374) who endorsed having a belief-changing psychedelic experience. The percentage of participants who identified as a “Believer (e.g., in Ultimate Reality, Higher Power, and/or God, etc.)” increased from 29 to 59% after the psychedelic experience. Taken together, findings suggest that DMT, ayahuasca, and psilocybin may strengthen some people’s belief in divine entities.

Sense of meaning

Two months after Griffiths et al. (2006) administered psilocybin to 36 participants, most participants (71%) rated their psilocybin session as among the top five most spiritually significant experiences of their lives. These findings were replicated by the same research group: About two-thirds of participants rated their psilocybin session as one of their top five most meaningful experiences two months after the session, and 58% responded similarly at the 14-month follow-up (Griffiths et al., 2008). In a subsequent experiment, most volunteers rated their psilocybin experience as highly personally and spiritually significant one month after sessions at the two highest doses; at 14 months, ratings were undiminished and consistent with community observer ratings (Griffiths et al., 2011).

More recent studies report similar findings. In a double-blind trial, Smigielski et al. (2019) administered either psilocybin or placebo to 39 participants at a 5-day mindfulness group retreat. At four-month follow-up, 50% and 35% of participants who took psilocybin rated their experience as among the ten or five most meaningful life experiences, respectively. Griffiths et al. (2018) found that approximately two-thirds of the sample rated their psilocybin session as among their five most meaningful experiences five months later. Likewise, Nicholas et al. (2018) found that 83% of participants rated their psilocybin session as one of their five most spiritually significant experiences, with persisting meaningfulness 30 days after their last dose.

Some people facing mental and physical health challenges also experience positive changes in meaning after using psychedelics. A small sample of cancer patients (n = 13) who received psilocybin reported a heightened sense of meaning and perspective even compared to life before their diagnoses (Swift et al., 2017). Among U.S. Special Operations Forces Veterans who engaged in a three-day clinical retreat in Mexico (Xin et al., 2023), ibogaine-and-5-methoxy-N,N-dimethyltryptamine treatment was associated with greater improvements in personal meaningfulness and spiritual significance from baseline to 1-month follow-up.

A qualitative study found that almost all Norwegian participants had faced at least one frightening or “bad” experience when using psilocybin (n = 36), LSD (n = 37), DMT (n = 20), 2C-B (n = 20), or MDMA (n = 34; Gashi et al., 2021). Yet, some believed their bad experiences provided deep existential and life-altering insights. Carbonaro et al.’s (2016) cross-sectional data showed similar effects, with personal meaning and spiritual significance positively related to the difficulty of the psychedelic experience and the degree of difficulty correlated with personal meaning (r = 0.41). Carbonaro et al. (2016) suggested that the duration of the challenging experience matters, as longer challenges associated negatively with personal meaning, spiritual significance, and well-being. Dosage also seemed to matter. At 6 months, compared to very low doses of psilocybin (n = 25), participants receiving high doses of psilocybin (n = 50) showed large significant positive changes in longitudinal measures of life meaning and purpose (Griffiths et al., 2018). Taken together, findings suggest that using psychedelics—in particular, psilocybin—can significantly increase one’s sense of spiritual meaning, even months or years after the psychedelic experience.

Spiritual faith or engagement in R/S practices

Griffiths et al. (2018) found large, significant, and positive changes in religious faith and daily spiritual experiences when two psilocybin sessions were paired with spiritual practices. Griffiths et al. (2011) administered psilocybin to 18 adults over five 8-h sessions spaced a month apart. At the 14-month follow-up, 71.6% reported the maximum possible Increased Spirituality score on the Persisting Effects Questionnaire. Very few (0.8%) scored comparatively on the Decreased Spirituality score. A double-blind between-group crossover study found that, on average, participants increased spiritual practice after psilocybin sessions (Griffiths et al., 2011). Moreover, Smigielski et al. (2019) found that psilocybin increased meditation depth and enhanced post-intervention mindfulness more than placebo four months after administering psilocybin at a mindfulness retreat. External ratings bolstered these findings.

DMT may also lead to increases in spiritual engagement. Using a self-report survey (n = 153), Corneille and Luke (2021) found that participants who endorsed spiritual awakenings while using DMT or psilocybin reported increased engagement with a variety of r/s practices following their experiences, including contact with nature, reading spiritual literature, mindfulness and meditation, yoga, and more. Furthermore, participants who took classic psychedelics (i.e., psilocybin, LSD, ayahuasca, or DMT) reported moderate to strong changes in spiritual practice (e.g., contemplative prayer, meditation) after their psychedelic session (Griffiths et al., 2019). These studies suggest that classical psychedelics—particularly psilocybin and DMT—can deepen belief, devotion, and engagement with r/s principles and practices.

Unity and self-transcendence

Kavenská and Simonová (2015) found that ayahuasca use associates with the development of intuition and an understanding of world unity. Prior engagement in r/s practices may underlie these effects: Compared to healthy non-meditating participants, psilocybin users who regularly meditate scored significantly higher on ratings of spiritual experience (66% vs. 22%), blissful state (86% vs. 48%), and feelings of unity (70% vs. 40%; Smigielski et al., 2019). In a study investigating psilocybin-occasioned mystical experiences in the treatment of tobacco addiction, open-ended responses seven days after the experience included themes related to unity, sacredness, and spiritual significance (Garcia-Romeu et al., 2014). Finally, self-dissolution predicted global changes in behavior and attitudes, with experiences of unity being a key component (Pokorny et al., 2017).

Underlying feelings of unity is a sense of self-transcendence, in which a person perceives the self going beyond the barriers of their body (St. Arnaud & Sharpe, 2023). As perceptions of the boundaries between the self and the external world dissolve, some people perceive the world as unified or harmonious. Self-transcendence includes changes in self-views (e.g., increases in self-acceptance or self-love), which appear to associate with psychedelic use (Lebedev et al., 2015). Semi-structured interviews investigating the perceived benefits of past ayahuasca use emphasized benefits like positive changes in self-knowledge, self-acceptance, self-love, inner serenity, and a sense of responsibility for one’s life (Kavenská & Simonová, 2015). Some participants even reported finding a deeper spirituality of being beyond oneself, leading to positive changes in life values. Furthermore, St. Arnaud and Sharpe (2023) found that classic entheogenic psychedelic use was associated with higher levels of spiritual seeking, self-transcendence, and psychospiritual development compared to non-entheogenic classic psychedelic use and non-use using a large international survey. These findings collectively illustrate that ayahuasca and psilocybin can enhance experiences of self-transcendence and unity for some users.

Positive changes in worldview

Davis et al. (2020) found that entity encounters occasioned by DMT produced profound and enduring changes in worldview, and Pokorny et al. (2017) found that using psilocybin changed the significance participants attributed to objects or their surroundings. In another study, 35% of the 176 participants commented on the health benefits of psilocybin use, including improved perspective, optimism, and an increased sense of spirituality (Carhart-Harris & Nutt, 2010).

These changes in worldview appear to be lasting for many participants. After testing 18 adults with five eight-hour psilocybin sessions spaced a month apart, researchers found that participants reported positive changes in attitudes, mood, and behavior one month after the sessions, especially at the highest doses (Griffiths et al., 2011). At a 14-month follow-up, changes were sustained and consistent with community observer ratings. Furthermore, mindfulness retreat participants in the psilocybin group reported greater changes in attitudes than the placebo group on an inventory measuring life changes (Smigielski et al., 2019). Findings were bolstered by post-hoc tests, which showed significantly higher scores on several scales, including appreciation for life, quest for meaning/sense of purpose, and appreciation of death. Smigielski et al. (2019) reported on other spiritual growth indicators, as well: The psilocybin group scored higher on the Concern for Others and Spirituality scales.

In a large cross-sectional survey (n = 1,606), participants rated attributions of consciousness to a range of living and non-living entities before and after a psychedelic experience (Nayak & Griffiths, 2022). There were large increases in attribution of consciousness to non-human primates (63–83%), quadrupeds (59–79%), insects (33–57%), fungi (21– 56%), plants (26–61%), inanimate natural objects (8–26%), and inanimate manmade objects (3–15%). Higher ratings of mystical experience associated with greater increases in the attribution of consciousness, and increased attributions were sustained years after the experience. Using a similar sample, Nayak et al. (2023) factor analyzed 45 belief statements, which revealed five factors. After a psychedelic experience, participants believed more in “Dualism” (β = 0.72), “Paranormal/Spirituality” (β = 0.90), “Non-mammal consciousness” (β = 0.72), and “Mammal consciousness” (β = 0.74). Increases in non-physicalist beliefs included belief in reincarnation, communication with the dead, existence of consciousness after death, telepathy, and consciousness of inanimate natural objects. Higher ratings of mystical experience were associated with greater changes in beliefs, and belief changes assessed after the experience (an average of 8.4 years) remained largely unchanged.

Converging cross-sectional, prospective observational and controlled research data suggest a relationship between psychedelic experiences and shifts away from hard physicalism and towards panpsychism, dualistic, and fatalistic beliefs (Timmerman et al., 2021). These changes persisted for up to six months in most domains. Authors found a positive correlation between shifts away from hard materialism and changes in well-being at four weeks and six months after the psychedelic ceremony. In another cross-sectional survey, participants who had tried psychedelics saw the potential for spiritual benefits, including increased belief in a world beyond the material realm and insights into ultimate reality (Exline et al., 2022). Overall, these findings indicate that psychedelic experiences can lead to profound and enduring shifts in worldview, which often correlate with a sense of improved well-being.

Connectedness with others

Lerner and Lyvers (2006) compared users of nonpsychedelic drugs like marijuana and amphetamines (n = 29), social drinkers who do not use illicit drugs (n = 66), and psychedelic drug users (n = 88) on questionnaires measuring values, beliefs, and emotional empathy. Psychedelic users scored significantly higher on mystical beliefs, having spirituality as a personal value, and concern for others. According to qualitative data from ayahuasca ceremony participants, an increased sense of connection to nature, love for living things, belief in a higher power, faith in maintaining peace, and social service could underlie these changes (Trichter et al., 2009).

Griffiths et al. (2008) compared psilocybin and methylphenidate administered in separate sessions, spaced two months apart. Psilocybin group participants scored significantly higher than the methylphenidate groups on positive attitudes about life and self, positive behaviors, and positive social effects two and 14 months after the sessions. According to community observer ratings, small positive attitude and behavior changes were observed two months post-psilocybin sessions but not post-methylphenidate sessions. After 14 months, the psilocybin group’s ratings of positive behavior, mood, attitude, and social changes were comparable to those observed two months after the session. Griffiths et al. (2011) also found that psilocybin users reported positive social changes, including better social relationships with family and others.

Some evidence suggests that psychedelics engender qualities like empathy (i.e., one’s perceived ability to identify and feel the emotions of others). In a cross-sectional study, psychedelic users scored higher on emotional empathy (measured as an outcome) than nonusers and users of other drugs, although only the comparison with nonusers was significant (Lerner & Lyvers, 2006). Other studies found close relationships between spirituality and positive social outcomes. For example, psilocybin-occasioned mystical experiences, along with spiritual practices like meditation, produced lasting changes in prosocial attitudes and behaviors (Griffiths et al., 2018). Compared with low doses of psilocybin, high-dose groups scored significantly higher on longitudinal measures of interpersonal closeness and community observer ratings. Authors concluded that psilocybin can occasion lasting trait-level increases in prosocial attitudes/behaviors and psychological functioning. Additionally, in a sample of 32 healthy participants, psilocybin significantly increased emotional empathy (Pokorny et al., 2017). This study also revealed significantly higher experiences of unity, spiritual experience, and changed meaning of percepts among those who took psilocybin relative to a placebo control group.

Shnayder et al. (2023) found that all three factors of the NIH-HEALS (Connection, Reflection & Introspection, and Trust & Acceptance) improved in response to psilocybin treatment. These effects were recorded one day after participants took psilocybin and were sustained for at least 8 weeks. The Connection factor, measuring connection to a higher power and to loved ones, increased by 12.7% on average by week 8. On the Watts Connectedness Scale (Watts et al., 2022), significant post-psilocybin increases were observed for total connectedness scores, as well as on each of its subscales. Compared with escitalopram, psilocybin therapy was associated with greater increases in connectedness scores.

Ayahuasca and MDMA may produce similar results. In one project, over half of ayahuasca ceremony participants attributed overall improvements in relationships with others to ayahuasca (Kavenská & Simonová, 2015). Participants believed these effects were due to the development of empathy, gratitude, unconditional love, compassion, tolerance, and honesty. Among Danish adults, psilocybin experiences were associated with subjective improvements in social relationships (Søgaard Juul et al., 2023). Respondents in the DMT group reported significantly greater persisting effects of their most memorable experiences on life satisfaction, social relationships, and meaning of life when compared to psilocybin and LSD. The DMT group also reported higher personal meaningfulness and spirituality. Finally, some spiritual seekers reported using MDMA for the compassion, empathy, and unconditional love they believed it fosters (Watson & Beck, 1991). In summary, findings indicate that substances like psilocybin, DMT, and MDMA can significantly enhance prosocial attitudes, empathy, and emotional connections, often resulting in lasting positive changes in social relationships and spirituality.

Reduced fear of death

When compared with non-psychedelically triggered religious, spiritual, and mystical experiences, experiences induced by psychedelics were rated as more mystical and resulted in a reduced fear of death, increased sense of purpose, and increased spirituality (Yaden et al., 2017). In another study, the psychedelic group was more likely to endorse a decreased fear of death than the non-drug group (70% vs. 57%; Griffiths et al., 2019).

Among people with a life-threatening diagnosis, psilocybin produced significant, enduring decreases in anxiety and depression (Griffiths et al., 2016; Ross et al., 2016). Adult participants with clinically elevated anxiety associated with a cancer diagnosis reported reconciliations with death after a single dose of psilocybin (Swift et al., 2017), and most participants made spiritual or religious interpretations of their experiences. In another study, psilocybin was administered to cancer patients experiencing psychological and existential distress (Agin-Liebes et al., 2020). Spiritual well-being, faith, meaning/peace, and death anxiety significantly improved 4.5 years after baseline measurements. In a randomized controlled trial, psilocybin-assisted psychotherapy (PAP) was associated with reductions in suicidal ideation and loss of meaning, reductions in cancer-related hopelessness and demoralization, and increased spiritual well-being (Ross et al., 2021).

Sweeney et al. (2022) directly compared psychedelic experiences and near-death experiences, both of which changed participants’ perspectives on death and dying. A large majority of participants in both groups (88% of the Non-Drug Group and 89% of the Psychedelic Group) reported that their experience resulted in decreased fear of death. Changes in death attitudes attributed to the experience were similar in both groups, including a reduced fear of death and high ratings of positive persisting effects and personal meaning and spiritual significance. Ayahuasca and DMT groups tended to report stronger and more positive effects than the psilocybin and LSD groups, which were comparable. Taken together, findings suggest that psilocybin, ayahuasca, and DMT may contribute to reduced fear of death and existential distress, particularly for individuals facing life-threatening illnesses.

Discussion

This review examined connections between psychedelic use and long-term spiritual growth. All major serotonergic psychedelics were considered, as were a variety of spiritual growth indicators. Results suggest that psychedelics are associated with distinctly spiritual benefits, including stronger perceived connections with the divine, a greater sense of meaning in one’s life, increased spiritual faith or engagement in r/s practices, enduring feelings of unity and self-transcendence, positive changes in worldview, increased connectedness with others, and reduced fear of death. Although relationships were observed between the consumption of psychedelic substances and spiritual growth, causality and direct benefit from this consumption cannot be assumed.

The trend toward spiritual growth could be rooted in mystical experiences, which are often induced by psychedelics. Profound mystical experiences might deepen one’s spiritual faith or inspire one to become more involved with r/s practices. Intense mystical experiences could also encourage people to confront and overcome existential anxiety, leading to a more profound and peaceful relationship with life and death. Mystical experiences might also lead individuals to feel interconnected with a greater spiritual reality, fostering a sense of unity with the divine. Although the specific role that mystical experiences play is still unclear, such experiences do appear to contribute to the relationship between psychedelic use and spiritual growth.

Of all the psychedelics studied, psilocybin was the most common, followed by ayahuasca and DMT. Psychedelic researchers reporting on spirituality have given classic psychedelics more attention than others (e.g., MDMA, ibogaine). This makes it unclear whether certain substances have stronger associations with specific indicators of spiritual growth, as we found few studies making direct comparisons between psychedelic substances (and these substances were rarely compared in controlled settings). Notably, many of the articles included a variety of substances but did not group participants based on the psychedelic they used. Two studies did not specify which substances their participants used. In some cases, though, researchers did compare and find meaningful differences in the spiritual effects of different psychedelics. For instance, when Sweeney et al. (2022) compared across substances, participants in the ayahuasca and DMT groups reported stronger and more positive enduring consequences of their psychedelic experiences than the psilocybin and LSD groups, which were largely indistinguishable.

As expected, many indicators of spiritual growth were closely related. For example, it was common for people who experienced an enduring sense of unity after taking psychedelics to also experience greater spiritual significance, feelings of awe, self-transcendence, and connectedness with others. Many studies that reported on one of these indicators also reported on others, implying a co-occurrence of several spiritual facets during and after psychedelic experiences. Positive changes in these indicators were sometimes dose-dependent, with higher doses relating to greater changes. Also, in some cases, people reported more long-term spiritual benefits if they had already participated in religious or spiritual practices, used psychedelics with spiritual intentions, or used psychedelics in religious or spiritual contexts.

The results of this review have potential implications for people who are experiencing spiritual struggles, which are experiences of tension, conflict, or strain that center on whatever people view as sacred (Exline, 2013; Pargament & Exline, 2022). Some psychedelic experiences may trigger spiritual struggles, such as religious doubts, concerns about demonic attacks, or threats to existing meaning systems. Yet psychedelics may help individuals grow spiritually or navigate spiritual struggles when they arise. We have found evidence for both of these possibilities in our ongoing research (Schutt et al., 2024). Carefully controlled and professionally facilitated psychedelic use may offer insights into spiritual struggles and could open the door to meaningful experiences that help people understand their place in the universe. For example, psychedelics might compel users to confront spiritual questions or problems they were avoiding, whether those questions are related to ultimate meaning, morality, doubt, or supernatural entities like God and the devil. By providing a different perspective on spiritual problems, psychedelics may help people answer religious questions or see their struggles from a new point of view. They could even give users a chance to confront spiritual struggles more directly—perhaps through personal exchanges with perceived supernatural entities.

Limitations and future directions

The results of this review should be considered in light of several limitations. There was an oversight during the literature review process: Though we kept track of the overall number of studies that were eliminated, we failed to methodically record how many studies were eliminated for specific reasons. For example, we cannot say exactly how many studies were eliminated because they measured immediate spiritual experiences rather than longer-term spiritual development. Our search was also limited to peer-reviewed articles accessible through PubMed and EBSCOhost Research Platform.

The studies to date also share a variety of limitations. Many studies were cross-sectional and used convenience samples. Several studies reported the likelihood of self-selection or other biases. Some participants may have been reluctant to disclose their opinions or past drug use. Furthermore, several studies collected data using online surveys, which are only available to people with reliable Internet access. Some studies used small or homogeneous samples (e.g., White, Western, and educated participants), and several articles failed to specify important demographic information like race/ethnicity and r/s orientation (see Table 3).

It is also worth mentioning that, for some sections of the current study (e.g., the Positive Changes in Worldview section), the extent to which spiritual changes were perceived as positive was unclear. Similarly, some of the studies included in this review—especially the survey and qualitative studies—are vague as to the exact nature of changes occasioned by psychedelics, as well as their strength and duration (e.g., Carhart-Harris & Nutt, 2010). These issues limit the generalizability of our results, and hence the conclusions we can draw from the data.

Future research can address these limitations and criticisms by leveraging longitudinal designs and in-depth analyses (e.g., structural equation modeling) to investigate how psychedelic use interacts with spirituality over time. It is also clear that some substances have received more research attention than others. Future research might focus on understudied psychedelics that show therapeutic promise (e.g., mescaline), perhaps using randomized controlled trials to compare the perceived spiritual effects of various substances over time. Also, whereas specific domains have been relatively well-studied regarding psychedelics and spirituality (e.g., existential meaning), other areas have received less attention. As previously mentioned, future research could target spiritual struggles (Exline et al., 2024; Schutt et al., 2024), which are widespread and linked with mental and physical health (see Pargament & Exline, 2021, 2022, for reviews). Psychedelics might trigger spiritual struggles or aid those struggling spiritually. For example, could one’s yearning for the mystical experiences associated with psychedelics clash with a conscience that warns against illegal drug use? Might experiences of oneness with the divine be helpful for people who feel that divine entities have abandoned them? Questions like these highlight the need for more targeted research across the spectrum of spiritual struggles.

Conclusion

This systematic review investigated relationships between psychedelic use and perceptions of long-term spiritual growth. Thirty-four peer-reviewed empirical studies were analyzed with 19,724 total participants. Results show that relationships between psychedelic use and spirituality exist, but these connections are complex. Links were found between serotonergic psychedelic use and various indicators of spiritual growth, including perceived connections with the divine, a greater sense of meaning in one’s life, increased spiritual faith or engagement in r/s practices, enduring feelings of unity and self-transcendence, increased connectedness with others, and reduced fear of death. A more tentative link was found between psychedelic use and positive changes in worldview. Sometimes, positive changes in these spiritual domains were more common at higher psychedelic doses (particularly for psilocybin) and for specific substances (i.e., psilocybin, DMT, and ayahuasca, which received more research attention in the included studies than other psychedelics). Mystical experiences were also important, with higher mystical experience ratings usually associating positively with indicators of spiritual growth after psychedelic use. Taken together, this review highlights several distinct ways in which psychedelics relate to spirituality and adds to a growing literature on the potential benefits of psychedelic use.