Psychedelic-Assisted Group Therapy : A Systematic Review, Alexander Trope et al., 2019

Psychedelic-Assisted Group Therapy : A Systematic Review

Alexander Trope, Brian T. Anderson, Andrew R. Hooker, Giancarlo Glick, Christopher Stauffer, Joshua D. Woolley

Journal of Psychoactive Drugs, 2019, 51, (2) 174–188.

doi : 10.1080/02791072.2019.1593559


Contemporary research with classic psychedelic drugs (e.g. lysergic acid diethylamide (LSD) and psilocybin) is indebted to the 20th century researchers and clinicians who generated valuable clinical knowledge of these substances through experimentation. Several recent reviews that highlight the contributions of this early literature have focused on psychedelic-assisted individual psychotherapy modalities. None have attempted to systematically identify and compile experimental studies of psychedelic-assisted group therapy. In therapeutic settings, psychedelics were often used to enhance group therapy for a variety of populations and clinical indications. We report on the results of a systematic review of the published literature in English and Spanish on psychedelic-assisted group therapies. Publications are characterized by their clinical approach, experimental method, and clinical outcomes. Given the renewed interest in the clinical use of psychedelic medicines, this review aims to stimulate hypotheses to be tested in future research on psychedelic-assisted psychotherapy, group process, and interpersonal functioning.

Keywords : Psychedelic; Hallucinogen; Psychotherapy; Group Therapy; Psilocybin; LSD



The use of psychedelics in group settings for religious purposes dates back centuries (Guerra-Doce 2015). It was through one of these traditional practices— the Mazatec communal ritual of the velada— that American researchers first learned of the psychoactive properties of the Psilocybe mexicana mushroom (Sabina and Wasson 1974). This discovery led to the isolation of, and early research with, psilocybin (Heim and Hoffmann 1958; Wasson and Riedlinger 1990). Famous “first wave” psychedelic research, namely Pahnke’s “Good Friday Experiment” (Pahnke 1963) and Leary’s “Concord Prison Experiment” (Leary et al. 1965), involved the administration of psilocybin in group settings. Despite this precedent, a group therapy approach has yet to be used in any published 21st-century clinical trial. To fill this knowledge gap, and complement other reviews of psychedelic research (Carhart-Harris and Goodwin 2017; Rucker, Iliff, and Nutt 2017; Rucker et al. 2016; Mangini 1998; Passie 1997, 2006), we conducted a systematic review of academic publications from 1900 to 2018 that employed a group element in the preparation, administration, or integration phases of psychedelic-assisted psychotherapy.

Group psychedelic use in nonclinical contexts (e.g., ayahuasca or peyote rituals) is beyond the scope of this review; however, the anthropological study of group psychedelic usage provides strong qualitative and ethnographic evidence of the safety and efficacy of using these substances when contained in a culture-affirming, ritual context (Dobkin de Rios 1972; Harner 1973; Labate and Cavnar 2014, 2016). MDMA, while not a classic psychedelic, is commonly mentioned alongside these substances and has its own extensive history of use in group contexts. Due to MDMA’s differential effects on social bonding, we have only included references to it in our systematic review when used in therapeutic sequences that also included use of a classic psychedelic.

The topic of group administration of psychedelics, and the utility of groups for the preparation or integration of psychedelic experiences, is important to several emerging trends in contemporary psychedelic research. Empirical qualitative findings from a recent clinical trial of psilocybin-assisted individual psychotherapy for treatment-resistant depression suggest that social connectedness may be a fundamental, underlying mechanism of therapeutic change (Watts et al. 2017; Carhart-Harris et al. 2018). Separately, another recent study administered psilocybin to healthy volunteers who received either “standard” psychological support, or a higher level of support that included more total contact hours with study facilitators and a regular “dialogue-group” with other participants who had received the study drug (Griffiths 2017). Participants in the enhanced support arm, compared to standard support, were both self- and observer-rated as demonstrating greater positive behavior changes attributed to their psilocybin experience. Moreover, participants from recent psychedelic-assisted individual psychotherapy trials have repeatedly requested to meet other participants (Bossis 2015; Bradberry et al. 2017) and have attested to the importance of these connections for corroborating often intense, difficult-to-describe, psychedelic experiences and reinforcing their beneficial effects (Bradberry et al. 2017). This echoes the clinical impression of early researchers that group involvement, whether in mutual aid groups like Alcoholics Anonymous or formal group therapy, could help solidify therapeutic gains by extending the intrapsychic experiences of high-dose psychedelic sessions into the interpersonal relationships of the group setting (Osmond et al. 1967). Non-medical psychedelic users in the community also increasingly seek out group support, as evidenced by the growth of peer- and therapist-led psychedelic integration groups.1 Lastly, as a pharmacological class, psychedelics show unique effects on interpersonal experience and behavior (Preller et al. 2018). Together, these trends suggest that incorporating groups into psychedelic therapy might enhance both participant satisfaction and outcomes.

Aside from group therapy’s cost- and time-saving efficiencies, equivalence between non-psychedelic individual and group therapy has been demonstrated for a range of clinical outcomes and styles of therapy (Burlingame et al. 2016; McRoberts, Burlingame, and Hoag 1998). Whether psychedelic-assisted group therapy is equivalent to individual approaches remains unknown. As psychedelic medicines enter pivotal trials in the United States and Europe, the prospect of post-approval clinical innovation with different administration modalities, including group therapy, arises. It is therefore imperative that data on the safety, feasibility and efficacy of group modalities are available to the rapidly evolving field of psychedelic-assisted psychotherapy.