The Canadian Network for Mood and Anxiety Treatments (CANMAT) Task Force Report: Serotonergic Psychedelic Treatments for Major Depressive Disorder

OBJECTIVE

Serotonergic psychedelics are re-emerging as potential novel treatments for several psychiatric disorders including major depressive disorder. The Canadian Network for Mood and Anxiety Treatments (CANMAT) convened a task force to review the evidence and provide a consensus recommendation for the clinical use of psychedelic treatments for major depressive disorder.

METHODS

A systematic review was conducted to identify contemporary clinical trials of serotonergic psychedelics for the treatment of major depressive disorder and cancer-related depression. Studies published between January 1990 and July 2021 were identified using combinations of search terms, inspection of bibliographies and review of other psychedelic reviews and consensus statements. The levels of evidence for efficacy were graded according to the Canadian Network for Mood and Anxiety Treatments criteria.

RESULTS

Only psilocybin and ayahuasca have contemporary clinical trials evaluating antidepressant effects. Two pilot studies showed preliminary positive effects of single-dose ayahuasca for treatment-resistant depression (Level 3 evidence). Small randomized controlled trials of psilocybin combined with psychotherapy showed superiority to waitlist controls and comparable efficacy and safety to an active comparator (escitalopram with supportive psychotherapy) in major depressive disorder, with additional randomized controlled trials showing efficacy specifically in cancer-related depression (Level 3 evidence). There was only one open-label trial of psilocybin in treatment-resistant unipolar depression (Level 4 evidence). Small sample sizes and functional unblinding were major limitations in all studies. Adverse events associated with psychedelics, including psychological (e.g., psychotomimetic effects) and physical (e.g., nausea, emesis and headaches) effects, were generally transient.

CONCLUSIONS

There is currently only low-level evidence to support the efficacy and safety of psychedelics for major depressive disorder. In Canada, as of 2022, psilocybin remains an experimental option that is only available through clinical trials or the special access program. As such, Canadian Network for Mood and Anxiety Treatments considers psilocybin an experimental treatment and recommends its use primarily within clinical trials, or, less commonly, through the special access program in rare, special circumstances.

Efficacy of ketamine intervention to decrease alcohol use, cravings, and withdrawal symptoms in adults with problematic alcohol use or alcohol use disorder: A systematic review and comprehensive analysis of mechanism of actions

BACKGROUND

Alcohol use disorder is highly prevalent and has important economical, societal, psychiatric, and medical consequences. All currently approved therapeutic approaches targeting alcohol dependence have relatively modest effects and high relapse rates. Recent evidence suggests that ketamine may be an effective intervention to treat alcohol use disorder and alcoholic withdrawal. This systematic review aimed to assess the current level of evidence for this intervention.

METHODS

This systematic review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered on the international database of systematic reviews PROSPERO. Medline(Ovid), CINAHL Complete(EBSCOhost), PsycINFO(Ovid), EBM Reviews(Ovid), EMBASE(Ovid), and Google Scholar were searched for studies using ketamine to treat harmful alcohol use, craving, or withdrawal states in humans. Studies of any methodology that evaluated ketamine in isolation or combination with other interventions were included. The risk of bias was assessed using specific Cochrane critical appraisal tools.

RESULTS

Of 1922 abstracts identified, 8 full-text articles were eligible for inclusion, yielding a total sample size of 634 participants. Five studies investigated the impact of ketamine on alcohol use and/or cravings and/or withdrawal in outpatient settings. Three studies looked at the effect of adding ketamine to conventional treatment of withdrawal symptoms in participants admitted to intensive care unit for severe alcohol withdrawal. Results on primary outcomes were mixed within and across trials.

CONCLUSIONS

Despite promising results, the current evidence does not permit definitive conclusions about the efficacy of ketamine in alcohol use disorders or withdrawal. Future studies are warranted.

Diagnosis of Autism Spectrum Disorder in Adolescents with Complex Clinical Presentations: A Montreal Case Series

Background:

Despite increased attention and recognition of autism spectrum disorders, many patients suffering from these disorders remain undiagnosed or are diagnosed late due to their subtle clinical presentation. The challenge for clinicians working in the field of mental health is not in screening and diagnosing young children showing typical signs of autism spectrum disorders, but rather in identifying patients at the high-functioning end of the spectrum whose intellectual abilities mask their social deficits.

Objective:

Because therapeutic interventions differ radically once the diagnosis of ASD has been made, it is important to understand the trajectory of those adolescents and identify clues that could help raise the diagnosis of ASD earlier.

Methods:

Records of eight adolescents with a late diagnosis of ASD were retrospectively reviewed to identify relevant clinical features that were overlooked in childhood and early adolescence.

Results:

The patients were previously misdiagnosed with multiple mental health disorders. These cases showed striking similarities in terms of developmental history, reasons for misdiagnosis, and the clinical picture at the time of ASD recognition. The cases were characterized by complex and fluctuating symptomatology, including depression, anxiety, behavioural problems, self-injurious behaviour and suicidal thoughts. Their Autism Spectrum Disorder (ASD) went previously undiagnosed due to the individual’s intelligence and learning abilities, which masked their social deficits and developmental irregularities. Signs of ASD were continuously present since childhood in all the eight cases. Once the developmental histories and the psychiatric evaluation of these adolescents were done by psychiatrists with appropriate knowledge of autism, the diagnosis of ASD was made.

Conclusion:

The ASD hypothesis should be raised in the presence of confusing symptoms that do not respond to usual treatment and are accompanied by an irregular developmental background. It is indeed a difficult diagnosis to make; however, the focused clinician can note subtle signs of ASD despite the intellectual learning of social codes. Family history, developmental irregularities, rigidity, difficulty in spontaneously understanding emotions, discomfort in groups and the need to be alone are significant indicators to recognize. Once the diagnosis has been considered, it must be confirmed or rejected by an experienced multidisciplinary team. The challenge for clinicians working in the field of mental health is not in screening and diagnosing young children showing typical signs of ASD, but rather in identifying patients who are at high-functioning end of the spectrum whose intellectual abilities mask their social deficits.

Music as an Intervention to Improve the Hemodynamic Response of Ketamine in Depression: A Randomized Clinical Trial

This randomized clinical trial explores whether music improves the hemodynamic response of ketamine among patients with treatment-resistant depression in Canada.

The impact of antidepressant treatment on the network structure of neurocognition and core emotional depressive symptoms among depressed individuals with a history of suicide attempt: An 8-week clinical study

BACKGROUND

A more in-depth understanding of the relationship between depressive symptoms, neurocognition and suicidal behavior could provide insights into the prognosis and treatment of major depressive disorder (MDD) and suicide. We conducted a network analysis among depressed patients examining associations between history of suicide attempt (HSA), core emotional major depression disorder, and key neurocognitive domains.

METHOD

Depressed patients (n = 120) aged 18-65 years were recruited from a larger randomized clinical trial conducted at the Douglas Institute in Montreal, Canada. They were randomly assigned to receive one of two antidepressant treatments (i.e., escitalopram or desvenlafaxine) for 8 weeks. Core emotional MDD and key neurocognitive domains were assessed pre-post treatment.

RESULTS

At baseline, an association between history of suicide attempt (HSA) and phonemic verbal fluency (PVF) suggested that HSA patients reported lower levels of the latter. After 8 weeks of antidepressant treatment, HSA became conditionally independent from PVF. Similar results were found for both the HAM-D and the QIDS-SR core emotional MDD/neurocognitive networks.

CONCLUSION

Network analysis revealed a pre-treatment relationship between a HSA and decreased phonemic VF among depressed patients, which was no longer present after 8 weeks of antidepressant treatment.

Imprinting: expanding the extra-pharmacological model of psychedelic drug action to incorporate delayed influences of sets and settings

Background

Psychedelic drug experiences are shaped by current-moment contextual factors, commonly categorized as internal (set) and external (setting). Potential influences of past environments, however, have received little attention.

Aims

To investigate how previous environmental stimuli shaped the experiences of patients receiving ketamine for treatment-resistant depression (TRD), and develop the concept of "imprinting" to account for such time-lagged effects across diverse hallucinogenic drugs.

Methods

Recordings of treatment sessions and phenomenological interviews from 26 participants of a clinical trial investigating serial intravenous ketamine infusions for TRD, conducted from January 2021 to August 2022, were retrospectively reviewed. A broad literature search was undertaken to identify potentially underrecognized examples of imprinting with both serotonergic and atypical psychedelics, as well as analogous cognitive processes and neural mechanisms.

Results

In naturalistic single-subject experiments of a 28-year-old female and a 34-year-old male, subjective ketamine experiences were significantly altered by varying exposures to particular forms of digital media in the days preceding treatments. Higher levels of media exposure reduced the mystical/emotional qualities of subsequent psychedelic ketamine experiences, overpowering standard intention-setting practices and altering therapeutic outcomes. Qualitative data from 24 additional patients yielded eight further spontaneous reports of past environmental exposures manifesting as visual hallucinations during ketamine experiences. We identified similar examples of imprinting with diverse psychoactive drugs in past publications, including in the first-ever report of ketamine in human subjects, as well as analogous processes known to underly dreaming.

Conclusions/interpretation

Past environmental exposures can significantly influence the phenomenology and therapeutic outcomes of psychedelic experiences, yet are underrecognized and understudied. To facilitate future research, we propose expanding the contextual model of psychedelic drug actions to incorporate imprinting, a novel concept that may aid clinicians, patients, and researchers to better understand psychedelic drug effects.

Clinical trial registration

ClinicalTrials.gov, identifier NCT04701866.

Intravenous ketamine for benzodiazepine deprescription and withdrawal management in treatment-resistant depression: a preliminary report

We present the first evidence that sub-anesthetic ketamine infusions for treatment resistant depression (TRD) may facilitate deprescription of long-term benzodiazepine/z-drugs (BZDRs). Long-term BZDR prescriptions are potentially harmful yet common, partly because of challenging withdrawal symptoms. Few pharmacological interventions have evidence for facilitating BZDR discontinuation, and none in patients actively suffering from TRD. In this ambi-directional cohort study, discontinuation of long-term (>6 month) BZDRs was attempted in 22 patients with severe unipolar or bipolar TRD receiving a course of six subanesthetic ketamine infusions over four weeks. We investigated the rates of successful BZDRs deprescription, trajectories of acute psychological withdrawal symptoms, and subsequent BZDRs abstinence during a mean follow-up of 1 year (primary outcome). Clinically significant deteriorations in depression, anxiety, sleep, and/or suicidality during the acute BZDR discontinuation phase were measured by repeated standardized scales and analyzed by latent growth curve models and percent correct classification analysis. Of the 22 eligible patients, all enrolled in this study and 91% (20/22) successfully discontinued all BZDRs by the end of the 4-week intervention, confirmed by urinary analyses. Less than 25% of discontinuers experienced any significant worsening of anxiety, depression, sleep difficulties, or suicidality during treatment. During follow-up (mean [range] duration, 12 [3-24] months), 64% (14/22) of patients remained abstinent from any BZDRs. These preliminary results suggest that ketamine infusions for TRD may facilitate the deprescription of BZDRs, even in patients with active depressive symptoms and significant comorbidity. Further investigation is warranted into this potential novel application of ketamine.

Increased Risks of Major Cardiac Adverse Events in Stimulant Use Disorder as Compared With Other Substance Use Disorders: A Propensity-score Matching Cohort Study

OBJECTIVES

Individuals with stimulant use disorders (StSUDs) present an elevated risk of cardiovascular complications compared with the general population. However, it remains unclear whether, within the subpopulation of individuals with substance use disorders (SUDs), those specifically affected by StSUDs face even higher cardiovascular complications.

METHODS

We conducted a retrospective cohort study using the EVERSANA databank, spanning from January 2015 to December 2023. The EVERSANA data set comprises deidentified electronic health record data aggregated and standardized across the United States. Participants included patients diagnosed with SUDs, encompassing alcohol, cannabis, opioids, stimulants, tobacco, hallucinogens, sedative-hypnotics, or inhalants. We employed the International Classification of Disease 10th (ICD-10) version codes to define the presence of StSUD and SUD. Major adverse cardiac events (MACE) were assessed, and Cox proportional hazard ratios were adjusted using high-dimensional propensity score (hdPS) matching to account for potential confounders.

RESULTS

Among 137,106 patients with SUD, 7706 (5.6%) had StSUD. The cohort was 50.2% female, 53.0% non-White, with a mean age of 49.1 years (SD±15). After adjustment, stimulant users exhibited significantly higher MACE rates (HR=1.37, 95% CI: 1.22-1.53, P <0.001), including an elevated risk of death (HR=1.23, 95% CI: 1.02-1.47, P =0.026).

CONCLUSION

Individuals with StSUD face increased MACE compared with those with nonstimulant SUDs.

Online Drug Markets and Implications for Addiction Medicine: A Narrative Literature Review

This narrative review examines the evolving landscape of online drug markets, focusing on darknet markets for illegal drugs and their implications for addiction medicine. We provide an overview of the development and current state of these markets, highlighting key features of their operation and the demographics of users. Finally, we address the implications for addiction medicine clinicians, including the need for adapted prevention efforts, new approaches to intervention and relapse prevention, and the potential for leveraging digital platforms in treatment. This review aims to equip addiction medicine professionals with the knowledge needed to navigate the challenges posed by online drug markets and to enhance their ability to provide effective care in this changing environment.

Ketamine for depression: a potential role in requests for Medical Aid in Dying?

Medical Aid in Dying (MAiD) is the act of a healthcare provider ending a patient's life, at their request, due to unbearable suffering from a grievous and incurable disease. Access to MAiD has expanded in the last decade and, more recently, it has been made available for psychiatric illnesses in a few countries. Recent studies have found that such psychiatric requests are rapidly increasing and primarily involve mood disorders as the primary condition. Nevertheless, MAiD for psychiatric disorders is associated with significant controversy and debate, especially regarding the definition and determination of irremediability - that a given patient lacks any reasonable prospect for recovery. In this article, we report the case of a Canadian patient who was actively requesting Medical Assistance in Dying for severe and prolonged treatment-resistant depression until she experienced remarkable benefits from a course of intravenous ketamine infusions. To our knowledge, this is the first report of ketamine or any other intervention yielding remission in a patient who would have otherwise likely been eligible for MAiD for depression. We discuss implications for the evaluation of similar requests and, more specifically, why a trial of ketamine warrants consideration.

Intravenous ketamine for treatment-resistant depression patients who have failed to respond to transcranial magnetic stimulation: A case series

BACKGROUND

For individuals with treatment-resistant depression (TRD), transcranial magnetic stimulation (TMS) has become a well-established approach. In the past decade, intravenous (IV) racemic ketamine has also emerged as a potential treatment for TRD. Currently, little data is available on the clinical effects of IV racemic ketamine in TRD patients who experienced TMS-failure.

METHODS

Twenty-one (21) TRD patients who had failed to respond to a standard course of high-frequency left-dorsolateral prefrontal cortex TMS were subsequently scheduled to received IV racemic ketamine infusions. The IV racemic ketamine protocol consisted of 0,5 mg/kg infusions over 60 min, 3 times a week over 2 weeks.

RESULTS

Treatment was safe with minimal side-effects. Mean baseline MADRS score was 27.6 ± 6.4 (moderate depression), decreasing down to 18.6 ± 8.9 (mild depression) post-treatment. Mean percent improvement was 34.5 % ± 21.1 from baseline to post-treatment. Paired sample t-test showed significant MADRS score decrease pre- to post-treatment [t(20) = 7.212, p < .001]. Overall, four (4) patients (19.0 %) responded and two (2) of those achieved remission (9.5 %).

LIMITATIONS

Limitations of this case series include its retrospective and uncontrolled open-label nature, the lack of self-rating and standardized adverse events questionnaires, as well as follow-ups beyond the immediate treatment period.

CONCLUSIONS

Novel ways to increase the clinical effects of ketamine are being explored. We discuss potential combination approaches of ketamine with other modalities to augment its effects. Given the global burden of TRD, novel approaches are needed to curb the current mental health epidemic around the world.

Efficacy and Safety of Modafinil for Treatment of Amphetamine-Type Stimulant Use Disorder: A Systematic Review and Meta-Analysis of Randomized Placebo-Controlled Trials: Efficacité et innocuité du modafinil pour le traitement des troubles liés à l'usage de stimulants de type amphétamine : revue systématique et méta-analyse d'essais randomisés contrôlés par placebo

INTRODUCTION

Amphetamine-type stimulants (ATSs) are related to significant harm worldwide, with limited effective pharmacological treatments for ATS use disorder (ATSUD). Modafinil has been explored as a potential treatment for ATSUD. This systematic review and meta-analysis (PROSPERO ID: CRD42023388487) aimed to evaluate the efficacy and safety of modafinil for the treatment of ATSUD.

METHODS

A comprehensive search of major indexing sources and trial registries, from inception to search date, was conducted on February 15, 2023, and updated on October 31, 2023. Eligible studies were randomized placebo-controlled trials (RCTs) of modafinil in individuals meeting the criteria for the Diagnostic and Statistical Manual of Mental Disorders, fourth and fifth editions, diagnoses of ATSUD. Eligible studies were assessed for risk of bias, using the Cochrane Risk of Bias tool. The primary outcome included the effect of modafinil on ATS use. Secondary outcomes included retention in treatment, ATS craving, treatment discontinuation due to adverse events (AEs), and serious AEs. Subgroup analysis by modafinil dose was conducted where appropriate. Risk ratio (RR) or Peto's odds ratio (OR) was calculated for the meta-analysis of dichotomous variables and standardized mean difference (SMD) was calculated for the random-effect meta-analysis of continuous variables.

RESULTS

Five RCTs (N = 451 participants) were included. Modafinil did not significantly impact ATS use (RR = 0.99; 95% CI, 0.97 to 1.02; p = 0.655), retention in treatment (RR = 1.02; 95% CI, 0.91 to 1.14; p = 0.799), ATS craving (SMD = -0.36; 95% CI, -1.19 to 0.47; p = 0.398), or treatment discontinuation due to AEs (Peto's OR = 0.48; 95% CI, 0.20 to 1.14; p = 0.100). These results were consistent across subgroup analyses. More episodes of serious AEs were reported in the modafinil group than in the placebo group, at higher doses (Peto's OR = 4.80; 95% CI, 1.18 to 19.56, p = 0.029).

CONCLUSION

There is currently no evidence suggesting that modafinil has a statistically significant effect on efficacy outcomes in populations with ATSUD. Continued research into effective treatments and harm reduction strategies for ATSUD is essential.

Elevated allostatic load is associated with poorer response to repetitive transcranial magnetic stimulation in treatment-resistant depression

This cohort study investigated whether allostatic load (AL) is associated with treatment response to repetitive transcranial magnetic stimulation (rTMS) in treatment-resistant depression (TRD). Pre-treatment blood samples measured AL across multiple systems. Pre- and post-treatment mood changes were assessed using the Montgomery-Åsberg Depression Rating Scale (MADRS). Associations between AL and treatment outcomes were explored. Higher pre-treatment AL was significantly associated with poorer post-treatment response status but was not significantly associated with smaller reduction in MADRS score after 4 weeks of treatment. Identifying biomarker profiles informed by the AL model could enhance treatment decisions in TRD, reducing risks associated with prolonged, ineffective rTMS trials and emphasizing the need for reliable predictive biomarkers.

Advancing research: a commentary on the untapped potential of acceptance and commitment therapy in alcohol use disorder treatment

Alcohol use disorder poses a significant global health threat, with profound consequences for individuals, families, and communities, necessitating continued exploration of novel treatment approaches. Acceptance and Commitment Therapy, an evidence-based approach for various mental health disorders, offers promise in addressing alcohol use disorder as well, but controlled trials are lacking, highlighting a crucial gap in research.

Trends in hallucinogen-associated emergency department visits and hospitalizations in California, USA, from 2016 to 2022

BACKGROUND AND AIMS

Hallucinogens encompass a diverse range of compounds of increasing scientific and public interest. Risks associated with hallucinogen use are under-researched and poorly understood. We aimed to compare the trends in hallucinogen-associated health-care use with alcohol- and cannabis-associated health-care use.

DESIGN, SETTING AND CASES

We conducted an ecological study with publicly available data on International Classification of Diseases, 10th Revision (ICD-10) diagnosis codes associated with emergency department (ED) visits and hospitalizations from the California Department of Healthcare Access and Information (HCAI). HCAI includes primary and secondary ICD-10 codes reported with ED or hospital discharge from every non-federal health-care facility licensed in California, United States, from 2016 to 2022.

MEASUREMENTS

ICD-10 codes were classified as hallucinogen-, cannabis- or alcohol-associated if they were from the corresponding category in the ICD-10 block 'mental and behavioral disorders due to psychoactive substance use'.

FINDINGS

Observed hallucinogen-associated ED visits increased by 54% between 2016 and 2022, from 2260 visits to 3476 visits, compared with a 20% decrease in alcohol-associated ED visits and a 15% increase in cannabis-associated ED visits. The observed hallucinogen-associated hospitalizations increased by 55% during the same period, from 2556 to 3965 hospitalizations, compared with a 1% increase in alcohol-associated hospitalizations and a 1% increase in cannabis-associated hospitalizations. This rise in hallucinogenic ED visits was significantly different from the trend in cannabis-associated (P < 0.001) and alcohol-associated (P = 0.005) ED visits. The hallucinogen-associated hospitalizations trend also significantly differed when compared with cannabis- (P < 0.001) and alcohol-associated (P < 0.001) hospitalizations.

CONCLUSIONS

Hallucinogen-associated emergency department visits and hospitalizations in California, USA, showed a large relative but small absolute increase between 2016 and 2022.

Effect of Cariprazine on Outcomes in Older-aged and Younger-aged Patients with Bipolar I Disorder: A Post-hoc Analysis

OBJECTIVES

To evaluate cariprazine in adults with older- and younger-age bipolar I disorder (OABD-I and YABD-I) and compare treatment effects between them.

DESIGN AND SETTING

Pooled post-hoc analysis of studies in depressive or acute manic/mixed episodes associated with bipolar I disorder.

PARTICIPANTS

475/1383 patients (34.3%) in 3 depression trials and 238/1037 patients (23.0%) in 3 manic/mixed trials were OABD-I.

INTERVENTIONS

Depression: placebo, cariprazine 1.5 mg/day, 3.0 mg/day, pooled 1.5-3.0 mg/day. Manic/mixed: placebo, cariprazine 3.0-6.0 mg/day, and 9.0-12.0 mg/day.

MEASUREMENTS

Montgomery-Åsberg Depression Rating Scale (MADRS), Clinical Global Impression of Severity (CGI-S), and Young Mania Rating Scale (YMRS).

RESULTS

In bipolar I depression, mean change from baseline in MADRS was significantly greater for the pooled cariprazine group vs. placebo in OABD-I (-13.72 vs. -11.98; p < 0.05) and for each cariprazine group vs. placebo among YABD-I. There was no significant difference in treatment effect between OABD-I and YABD-I for either individual cariprazine group vs. placebo. For mania/mixed states, mean change in YMRS was significantly greater for cariprazine 3.0-6.0 mg/day vs. placebo in OABD-I (-19.04 vs. -12.45; p < 0.001) and for both cariprazine groups in YABD-I (-12.49, -19.66 and -18.05 for placebo, cariprazine 3.0-6.0 mg/day and 9.0-12.0 mg/day, respectively [both p < 0.0001 vs. placebo]). There was no significant difference in treatment effect between OABD-I and YABD-I for cariprazine 3.0-6.0 mg/day vs. placebo; there was a significantly higher treatment effect for cariprazine 9.0-12.0 mg/day vs. placebo in the YABD-I subpopulation vs. OABD-I (4.20; p < 0.05).

CONCLUSIONS

Cariprazine appears to be effective for both depressive and manic/mixed episodes of bipolar I disorder, regardless of age.

The ketamine chameleon: history, pharmacology, and the contested value of experience

INTRODUCTION

Since its synthesis in 1962, ketamine has been widely used in diverse medical contexts, from anesthesia to treatment-resistant depression. However, interpretations of ketamine's subjective effects remain polarized. Biomedical frameworks typically construe the drug's experiential effects as dissociative or psychotomimetic, while psychedelic paradigms emphasize the potential therapeutic merits of these non-ordinary states.

AREAS COVERED

Ketamine's psychoactive effects have inspired diverse interpretations. In this review, we trace the historical evolution of these perspectives - which we broadly categorize as 'dissociative,' 'dream-like,' and 'psychedelic' - and show how they emerged out of these clinical contexts. We highlight the influence of factors such as language, dose, and environmental context on ketamine's effects and therapeutic outcomes. We discuss potential mechanisms underlying these context-dependent effects and explore the broader clinical and research-related ramifications.

EXPERT OPINION

Ketamine's subjective effects are undeniably powerful, yet their therapeutic significance remains debated. A nuanced, interdisciplinary approach is essential for maximizing ketamine's potential. Future research should focus on how explanatory models, treatment environments, and patient preparation can optimize ketamine's benefits while minimizing distress. We suggest that, rather than being a tiger to be tamed as its creator once described, ketamine may best be understood as a chameleon whose color shifts depending on its context.