The psychotherapeutic method used in this study was a continuous process lasting several months. Two preparatory psychotherapy sessions served to discuss the participant’s history, social situation, personality, health, mind-set, and emotional situation, also known by the term set (Zinberg, 1986). These also served to explain the action of LSD and structure of the setting, answer questions, and build therapeutic alliance.
The physical environment within which the experimental sessions took place was a safe, quiet, and pleasant room in a private practice office. The participant was advised to lie on a mattress on the floor or sit comfortably on a chair. Other than going to the bathroom, the participants remained in the treatment room for the entire 8-hour experimental session and overnight with an attendant nearby.
LSD was supplied as free base by Lipomed (Arlesheim, Switzerland). Capsules consisting of 200 μg (experimental dose) and 20 μg of LSD (active placebo) were prepared by Bichsel Laboratories (Interlaken, Switzerland). Quality control, randomization, and blinding were performed by R. Brenneisen, PhD, at the Department of Clinical Research, University of Bern, Switzerland. Capsules were of identical size, color, and shape and were bottled in sequentially numbered containers.
The primary intervention consisted of two full-day experimental sessions scheduled 2 to 3 weeks apart with a male/female co-therapist team, embedded within an ongoing process of drug-free psychotherapy sessions for preparatory and integrative purposes.
The participants were randomly assigned to the experimental dose groups, receiving either an oral dose of 200 μg of LSD (n = 8) or an active placebo of 20 μg of LSD (n = 4). The experimental dose was a moderate amount expected to produce the full spectrum of a typical LSD experience, without fully dissolving normal ego structures. The 20-μg dose of LSD was chosen as an active placebo to produce short-lived, mild, and detectable LSD effects that would not substantially facilitate a therapeutic process. The participant, the co-therapists, and the independent rater were blinded to condition assignment.
The participants were required to taper off of antidepressants and antianxiety medications, to avoid alcohol and recreational drugs for 24 hours before, and to abstain from driving for 24 hours after the experimental sessions. On the morning of the experimental sessions, the participants arrived at the office for a short discussion about their current mood and mental state and a urine drug test (Drug Screen Multi5A: amphetamine, cocaine, morphine, methamphetamine, tetrahydrocannabinole; nal von minden GmbH, Moers/Germany). If the subjects tested positive, the session would have been postponed, but this did not occur. After LSD administration, the participants were instructed to focus their awareness and mindful attention inward to follow their personal process of perception, emotion, and cognition. Lengthy discussions between the participants and the co-therapists were discouraged during the acute effects of the LSD. Approximately two thirds of each LSD-assisted experimental session was focused inward with music played to deepen self-awareness and facilitate emotional processing, and one third contained brief conversations. The therapeutic session ended after 8 hours, when the acute effects had subsided, followed by a brief review of the day’s experiences.
After each experimental session, three drug-free psychotherapy sessions lasting 60 to 90 minutes took place, during which the participant’s experiences were reviewed for integration and deepening the therapeutic process. Two months after the second experimental session, a follow-up evaluation was completed, and the treatment period was finished by breaking the blind for each individual. The participants who received the active placebo could cross over to an identical but open-label treatment with 200 μg of LSD. A long-term follow-up evaluation was conducted 12 months after the last experimental session with LSD in either the blinded portion of the study or the open-label crossover.
A nurse collected heart rate and blood pressure measurements during experimental sessions. After two experimental sessions, a follow-up physical examination was performed by the participant’s physician. Throughout the study, adverse events (AEs) were collected, and related AEs were recorded during experimental sessions and at the integrative session on the day after. The related AEs contained both AEs that were disturbing for the participant and those that belong to the mode of action of LSD (e.g., visual patterns). Concomitant medications used to treat anxiety, depression, and pain before the study and in between experimental sessions were documented. The subjects tapered off of these types of concomitant medications approximately five half-lives before each experimental session.
The independent rater, an experienced clinical psychologist, conducted the SCID to establish psychiatric diagnoses at screening (Wittchen et al., 1997). The STAI Form X, a widely used self-report instrument for assessing state and trait anxiety in adults, served as the primary outcome measure of anxiety symptoms. Secondary outcome measures included the European Cancer Quality of Life Questionnaire 30-item version 1.0 (EORTC-QLQ-30; Aaronson et al., 1993), the SCL-90-R (Schmitz et al., 2000), and the Hospital Anxiety and Depression Scale (HADS; Herrmann-Lingen et al., 2011). Outcome measures were completed at baseline, 1 week after experimental sessions, 2-month follow-up, and 12-month follow-up. The participants completed a daily dairy on changes in medication, adverse effects of LSD or medications, and pain using the Visual Analog Pain Scale. After each experimental session, the State of Consciousness Questionnaire was completed (Griffiths et al., 2006).
The statistical software Statistical Package for the Social Sciences for Windows, version 18.0 (IBM Corp, New York), was used. Repeated-measures analysis of variance (ANOVA) was used to test for significant changes in anxiety from baseline to subsequent posttreatment measurements. STAI trait and STAI state were analyzed in separate ANOVAs. To account for multiplicity, the alpha level indicating significance was adjusted to 0.025 (two tailed). Effect sizes were estimated using Cohen’s d techniques. Results of the 12-month follow-up were compared with those of the 2-month follow-up with paired t-tests. Secondary outcome measures conducted for exploratory purposes were not used for significance testing to reduce multiplicity.
We were unable to obtain results for two subjects (one experimental dose, one active placebo) from the assessment conducted 1 week after the second experimental session because of intervening cancer treatments. To avoid substantially reducing the sample size because of missing data, the assessment 1 week after the second experimental session was dropped for all subjects from analysis of outcomes. One active placebo participant was excluded from analysis after completing all study procedures because of a correction in the diagnosis of the qualifying disease state, which no longer satisfied the inclusion criteria.
For STAI trait, Mauchly’s Test of Sphericity was not significant (p = 0.824) and sphericity was assumed. No significant difference was found (p = 0.261) between group mean scores at baseline. The visit × group interaction testing for differences between the groups produced p = 0.033 (F = 4.151, df = 2,18), and observed statistical power was 65.6%, with results trending toward statistical significance. Comparing trait anxiety at baseline with 2-month follow-up yielded an effect size of 1.1. However, only three of eight experimental dose subjects dropped lower than the threshold value of 40 after the intervention. In contrast, all active placebo subjects experienced increases in trait anxiety. Figure 2 shows a clear linear relationship between visit and mean trait anxiety for the experimental dose group, whereas no such relationship exists for the active placebo group. Comparison of 2-month and 12-month follow-up results in the subjects who received 200 μg of LSD in either the blinded sessions or the open-label crossover indicate that the benefits were sustained over time. The mean difference varied only by 0.667 between these assessments, and no significant difference was found with p = 0.825 (two tailed).
For STAI state, Mauchly’s Test of Sphericity was not significant (p = 0.813), and sphericity was assumed. No significant difference was found between the groups at baseline (p = 0.563). The visit × group interaction testing for differences between the groups produced p = 0.021 (F = 4.846, df = 2,18), and observed statistical power was 72.7%. Even controlling for multiplicity, the reductions in state anxiety were statistically significant 2 months after two experimental sessions of LSD-assisted psychotherapy. Comparing state anxiety at baseline with 2-month follow-up yielded an effect size of 1.2. However, only three of eight experimental dose subjects dropped lower than the diagnostic cutoff of 40 after the intervention. In contrast, two active placebo subjects experienced increases in state anxiety. Figure 2 shows a clear linear relationship between visit and state anxiety for the experimental dose group, whereas no such relationship exists for the active placebo group. Comparison of 2-month and 12-month follow-up results in the subjects who received 200 μg of LSD in either the blinded sessions or the open-label crossover indicates that the benefits were sustained over time. The mean difference varied only by 1.00 between these assessments, and no significant difference was found with p = 0.531 (two tailed).
Changes in secondary outcome measures were not analyzed for statistical significance because of concerns about multiplicity. However, the results obtained from these measures were, overall, quite supportive of the STAI results (Table 2). Global health scores from the EORTC-QLQ increased from a mean (SD) of 37.4 (10.0) at baseline to 50.0 (14.9) after treatment with two sessions of 200 μg of LSD, whereas mean scores decreased from 44.3 (12.7) to 36.0 (12.8) in the active placebo group. Scores increased on average in the subjects who received 200 μg of LSD treatments and continued to 12-month follow-up, indicating that most of the subjects receiving the experimental dose were able to attain and maintain comparable quality of life with the general European population by participating in this study (Scott et al., 2008).
The SCL-90-R is a widely used measure of overall psychological problems and psychopathology. Global Severity Index (GSI) scores from the SCL-90-R decreased from a mean (SD) T-score of 69.6 (6.7) at baseline to 60.2 (7.2) in the experimental dose group whereas increasing from 66.0 (15.1) to 67.7 (10.2) in the active placebo group. The active placebo group experienced an improvement comparable with the full-dose group after receiving the experimental dose in the open-label crossover, with mean (SD) T-scores dropping to 57.3 (15.0). Both Positive Symptom Distress Index (PSDI) and Positive Symptom Total (PST) scores from the SCL-90-R mirrored these improvements, indicating that overall psychopathology improved in this subject sample 2 months after treatment.
The HADS results were also generally supportive of overall improvements in this subject sample. The experimental dose group mean (SD) anxiety scores decreased from 11.7 (3.4) to 8.1 (3.2) after two sessions, whereas the active placebo group anxiety scores decreased only from 11.3 (2.1) to 10.7 (3.0). The active placebo subjects who continued to the crossover experienced an even greater decline lower than the diagnostic cutoff for anxiety to 7.0 (2.6). All subjects who received the experimental dose were lower than the diagnostic cutoff at the 12-month follow-up, with a mean (SD) of 7.6 (4.5). The depression results also mirrored the anxiety results. Overall, the secondary outcome measures of the study were useful in supporting the results of the primary outcome measure.
For all 24 blinded sessions, all participants correctly guessed the dose of LSD that was administered, and both therapists guessed incorrectly in one active placebo session. The therapists were “very certain” in 22 sessions, “certain” in 1 session, and “somewhat certain” in 1 session. The participants were “very certain” in 20 sessions, “certain” in 1 session, “somewhat certain” in 2 sessions, and “not at all certain” in one session. This indicates that the 20-μg dose was too low to achieve successful uncertainty about the dose.
Neither the experimental dose (200 μg of LSD) nor the active placebo (20 μg of LSD) produced any drug-related severe adverse events, that is, no panic reaction, no suicidal crisis or psychotic state, and no medical or psychiatric emergencies requiring hospitalization. Related AEs (Table 3) included both positive and negative effects commonly associated with LSD. The experimental dose subjects experienced more types of AEs (n = 18) than the active placebo subjects (n = 8). In general, AEs were reported more frequently and with increased intensity in the experimental dose sessions. Interestingly, fewer reports of anxiety were received during experimental sessions with 200 μg (22.7%) than with active placebo (50%), and the mean intensity of anxiety was comparable between the groups. However, the subjects reported experiencing mild-to-moderate emotional distress similarly in experimental dose sessions (36.4%) and active placebo sessions (33.3%). Most AEs resolved when drug effects diminished. Only six reports of mild related AEs (illusions, feeling cold or abnormal, and some emotional distress) persisted until the next day. No flashback phenomena or other prolonged effects were observed.
During the study, two participants (both experimental dose) received concomitant selective serotonin reuptake inhibitor (SSRI) treatment for depression and tapered off of these medications five half-lives before each experimental session because SSRIs may attenuate the effects of the serotonergically active experimental drug (Bonson et al., 1996). Three participants received benzodiazepines (two experimental dose and one active placebo) as needed. Three participants received pain medication during the study, only one of which was required as rescue medication for a treatment-emergent AE. Acetaminophen was required for this participant for a moderate headache the day after an experimental dose session.
Physiological measures were recorded for all participants during experimental sessions. Consistent with the previous findings (Kornetsky, 1957; Sokoloff et al., 1957), LSD did not significantly alter blood pressure or heart rate (Table 4).
All research with LSD-assisted psychotherapy in the 1950s and the 1960s came to a halt by the early 1970s. Our study, the first in more than 40 years to evaluate safety and efficacy of LSD as an adjunct to psychotherapy, was conducted in participants with anxiety after being diagnosed with a life-threatening illness. In contrast to the shortcomings of older studies, we used a controlled, randomized, and blinded study design to meet contemporary research standards. LSD was given in a psychotherapeutic context to facilitate a deep psychedelic state, allowing the participant to encounter his/her own inner realities during an emotionally intensified dream-like “journey.”
In our study, using appropriate inclusion/exclusion criteria, detailed participant preparation, and a carefully supervised experience in a supportive psychotherapeutic setting, psychological side effects were mild and limited. There were no AEs often attributed to LSD such as prolonged anxiety (“bad trip”) or lasting psychotic or perceptional disorders (flashbacks). Congruent with studies in the past (Hintzen and Passie, 2010), the few mild somatic effects of LSD such as changes in heart rate and blood pressure were of no clinical significance.
The primary outcome variable in this study was of the STAI anxiety measure. Patients with life-threatening illnesses confront an existential threat from shortened life expectancy that often causes periods of suffering, pain, and anxiety. Congruent with earlier studies (Pahnke et al., 1970), the results in the experimental dose group show a significant reduction in state anxiety, as experienced on a daily basis. Furthermore, the more stable personality-inherent feature of anxiety proneness (trait anxiety) showed a strong trend toward reduction. Trait anxiety is not expected to be altered by short-term psychotherapy (Spielberger et al., 1970), but a comparable finding was reported in recent research with psilocybin in cancer patients that reported significant reductions of trait anxiety (although without correction for multiplicity) but not state anxiety (Grob et al., 2011). Therefore, this trait change may be supported by neurobiological effects of adjunctive use of LSD, which was originally introduced for deepening and accelerating psychotherapeutic processing (Abramson, 1967) and, in some studies, was shown to alter personality traits (MacLean et al., 2011; McGlothlin et al., 1967; Savage et al., 1966).
In this study, the experimental dose reduced anxiety when administered in either the blinded treatment or the open-label crossover for the active placebo subjects. These results were stable over time as shown by the 12-month follow-up. Eleven of 12 participants treated were LSD-naive. A moderate dose (200 μg) provided a psychologically manageable first LSD experience. Most of the participants stated a preference for more than two LSD sessions and a longer treatment period. The results demonstrated a decrease in STAI scores most prominently after the second LSD session, suggesting that at least two LSD sessions are needed to demonstrate these effects. A longer treatment period with additional LSD sessions and larger doses may be indicated (Gasser, 1996).
Limitations of the Study
As a pilot study, this study had limited sample size, which reduced precision in effect size estimates and significance testing. The sample size selected was sufficient for a study primarily focused on safety and feasibility. The imperfect blinding also limits the validity of the results. The problem of the double blind in studies with pharmacologically active substances is a well-known methodological challenge (Mogar, 1967; Salzman, 1969). LSD is a potent psychoactive drug, and participants and therapists are likely to detect whether an experimental dose or an inactive placebo or active placebo of very low dose of LSD was administered. Although using a slightly higher LSD dose in the comparator group can increase blinding, it can also increase efficacy of the comparator, compromising the estimates of effect size. Given the safety of the moderate experimental dose, results might have been improved with a larger dose of 250 μg. Other limitations exist in treating participants with grave somatic diseases because the course of the somatic illness (e.g., worsening or improving) may substantially impact psychological parameters independent of the therapeutic intervention and contribute to missing data. The quality of life questionnaire (EORTC-QLQ), which was chosen as a secondary outcome measure, focuses extensively on physical aspects and was insufficient for evaluating long-term psychological changes. Future studies should include a quality of life measure that focuses on psychological well-being more so than physical aspects of quality of life in this population.
This pilot study in participants with anxiety associated with the diagnosis of a life-threatening illness has demonstrated safety in 22 psychotherapy sessions assisted by 200 μg of LSD with no drug-related severe adverse events. Group comparison results support positive trends in reduction of anxiety after two sessions of LSD-assisted psychotherapy, with effect size estimates in the range of 1.1 to 1.2. In view of promising historical studies with adjunctive LSD treatment in this population and a recent promising study using psilocybin (Grob et al., 2011), as well as the urgent need for more effective treatments of anxiety in these participants, further study is warranted into the potential of LSD-assisted psychotherapy.
The authors thank B. Speich, M. Jegerlehner, and K. Haenseler for study management and C. Blank and K. Kirchner for study coordination.
The authors dedicate this article to Albert Hofmann, discoverer of LSD, for whom this study and the resumption of research into LSD’s therapeutic potential was “a fulfillment of a longtime wish.”
This study was funded in part by Schweizerische Aerztegesellschaft für Psycholytische Therapie (Swiss Medical Society for Psycholytic Therapy) and Multidisciplinary Association for Psychedelic Studies.
Rick Doblin (president) and Berra Yazar-Klosinski are employees of the main sponsor MAPS. Peter Gasser is president of SAEPT.
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Keywords:© 2014 by Lippincott Williams & Wilkins
LSD; psychedelic; psycholytic therapy; hallucinogen; anxiety disorder