This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Psilocybin-Assisted Therapy for the Treatment of Cancer-Related Anxiety in Patients With Metastatic Cancer (NCT05847686), a na phase 1, phase 2 study. The primary outcome is Number of Instances of Potentially Unattended Psilocybin-related Distress During Psilocybin Sessions..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05847686 |
| Phase | Phase 1, Phase 2 |
| Condition | Hematopoietic and Lymphatic System Neoplasm, Metastatic Malignant Solid Neoplasm |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 55 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Washington |
| Results posted | Yes |
2. Clinical Question
Population
Patients with metastatic cancer and symptoms of anxiety and/or depression. The registry lists hematopoietic and lymphatic system neoplasm and metastatic malignant solid neoplasm among the conditions. Enrollment is recorded as 55.
Intervention
Psilocybin by mouth alongside group and individual therapy sessions. Counseling and questionnaire administration are also listed as interventions. The registry describes the psilocybin as derived from Psilocybe cubensis using a patented process to produce a pharmaceutical-grade version.
Comparator
There is no separate comparator group. The study is listed as single-group, with allocation recorded as not applicable and masking as none. It therefore does not make a randomized, like-for-like comparison with another treatment or with a control condition.
Primary question
During the psilocybin administration session on Day 0, how many instances of participant distress in a small group require one-to-one facilitator attention that cannot be met by the four-person facilitation team? This is a group-session safety and staffing question, not a direct measure of anxiety improvement.
The study is titled “Psilocybin-Assisted Therapy for the Treatment of Cancer-Related Anxiety in Patients With Metastatic Cancer.” Its official title describes a phase 1/2 study of a group model of psilocybin-assisted therapy. The registry describes the study as testing safety and side effects in patients with metastatic cancer and symptoms of anxiety and/or depression. Hospital Anxiety and Depression Scale (HADS) change is listed as a secondary outcome, but a numerical result for that outcome is not reported in the registry record.
The central statistical question is whether the group-session delivery model can be described in terms of distress episodes that exceed the facilitation team's capacity. Because no control group is included, the design cannot estimate a between-group treatment effect. Nor does the primary outcome itself establish whether anxiety changed: its unit is events, and its definition concerns the need for additional facilitator attention during the session.
3. Trial Design
This is a phase 1/2 interventional study with a single-group model. The registry records allocation as not applicable and masking as none. Participants in the treatment group receive psilocybin by mouth and take part in group and individual therapy sessions. The registry also lists counseling and questionnaire administration. No parallel control arm is described, so the study is not a randomized comparison and its treatment group cannot be interpreted against a concurrent like-for-like control.
The registry lists enrollment as 55. The recorded study start date is 2023-06-27, primary completion date is 2024-04-08, and status is completed. These registry entries describe the registered study record; they do not establish when every participant was assessed or when all analyses were conducted.
The primary outcome is a count of instances of potentially unattended psilocybin-related distress during psilocybin sessions. It is assessed at the administration session on Day 0. Distress qualifies when it requires one-to-one facilitator attention that cannot be met by the four-person facilitation team. Small group sizes are described as varying over the course of the study, and backup facilitators are to be available when the situation occurs. The outcome description says descriptive statistics will be used and that the measure will be tabulated on Day 0 after each group intervention.
HADS change in measured anxiety and depression is listed as a secondary outcome. The registry record does not report the time points or detailed scoring approach for that secondary outcome. It also does not report a fuller statistical analysis plan, a sample-size justification, or the intended analysis populations. Since this is a single-group study, observed changes during follow-up, if reported, would not by themselves distinguish a treatment effect from other explanations such as time, concurrent care, or the course of illness.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | Treatment (Psilocybin, Therapy) |
|---|---|
| STARTED | 55 |
| COMPLETED | 52 |
| NOT COMPLETED | 3 |
Reasons for not completing this period:
| Reason | Treatment (Psilocybin, Therapy) |
|---|---|
| Withdrawal by Subject | 3 |
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Treatment (Psilocybin, Therapy) |
|---|---|---|
| Participants analysed | 52 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 48 |
| Age, Categorical: >=65 years | Participants | 4 |
| Age, Continuous | years | 53 (26 to 80) |
| Sex: Female, Male: Female | Participants | 32 |
| Sex: Female, Male: Male | Participants | 20 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 3 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 49 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 1 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 1 |
| Race (NIH/OMB): White | Participants | 49 |
| Race (NIH/OMB): More than one race | Participants | 1 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Hospital Anxiety and Depression Scale | units on a scale | 17.5 (SD 5.99) |
6. Primary Endpoint
The registry lists the primary outcome as Number of Instances of Potentially Unattended Psilocybin-related Distress During Psilocybin Sessions., measured over At psilocybin administration session on day 0.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Events |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint counts instances of participant distress during the Day 0 psilocybin administration session that require one-to-one facilitator attention beyond what the four-person facilitation team can provide. Its unit is events. The definition focuses on a practical safety concern in a group setting: whether a participant's distress may call for more individual support than the assigned team can deliver at that moment.
This endpoint is useful for describing the operational demands of group delivery. A count can convey how often the defined situation arose during the sessions, while the outcome definition makes clear what qualifies as an event. The registry says small group sizes vary and that backup facilitators will be available when the situation occurs. Those details matter when interpreting a count because the number and context of opportunities for an event can vary across group interventions.
The endpoint does not measure the severity of every distress experience, overall tolerability, or change in anxiety. It also does not directly indicate whether additional backup support was actually needed or how long support lasted. The posted outcome description specifies a threshold for facilitator capacity, not a broader clinical definition of distress. The numerical primary-outcome result, including the observed event count, is not reported in the registry record. Therefore, the endpoint's definition can be explained, but its observed frequency cannot be assessed from this record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a completed, phase 1/2, single-group study, but a numerical result for the primary endpoint is not reported in the registry record. Consequently, the frequency of qualifying distress events cannot be stated, and the record does not support a conclusion about how often the defined facilitator-capacity threshold was reached. The primary endpoint is a count of events during the Day 0 administration session, not a comparison of anxiety scores between treatment groups.
There is no comparator arm. Any within-group change in symptoms, if one were available, would describe change over time among participants in this study but would not isolate the effect of psilocybin-assisted therapy from other influences. The registry lists HADS change in anxiety and depression as a secondary outcome, but it does not report a numerical result for that outcome in the registry record recorded. That leaves neither the primary event count nor the secondary symptom change available for quantitative interpretation.
The safety record lists 52 participants at risk for serious adverse events, with 3 affected, and 52 at risk for other adverse events, with 30 affected. It also lists 2 deaths. The serious adverse-event terms with the highest reported percentages are Death at 3.8% and dehydration at 1.9%. These entries should be read as registry safety reporting, not as proof that an event was caused by the study intervention. The record does not provide the case narratives, timing, attribution, or a comparison group needed to assess causality. The death count and the serious-event term Death should not be assumed to describe separate cases or separate kinds of events.
The registry states that the primary outcome was to be analyzed descriptively. It does not report the resulting count or other descriptive statistics. Without the observed primary result, uncertainty measures, or details of the analysis population, statistical precision cannot be judged. In particular, a completed status does not by itself mean that all outcome results are available in the record.
Planning illustrations are distinct from observed trial evidence. The stated assumptions for such illustrations include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect defined as a fraction of the observed effect. These are planning assumptions, not evidence that this single-group trial had a randomized two-arm analysis or achieved a particular power. The registry record does not report a sample-size justification for this study, and the observed effect needed to interpret such illustrations is not reported in the registry record.
9. Statistical Methods Explained
The primary outcome is a count, because it records the number of qualifying distress instances rather than a continuous measurement such as a score. Counts are often analyzed with descriptive summaries when the goal is to report how many events occurred. The registry's outcome description explicitly says descriptive statistics will be used and that the result will be tabulated on Day 0 after each group intervention. It does not identify a specific probability model, a confidence interval method, or a formal hypothesis test for the primary outcome.
What does a count outcome describe?
A count records event frequency over a defined observation context. Here, that context is the psilocybin administration session on Day 0, and a qualifying event is distress that requires one-to-one facilitator attention beyond the four-person facilitation team's capacity. Such a count is meaningful only alongside its event definition and observation context. The registry notes that group sizes vary over the study. This means the number of participants and circumstances exposed to the group-session setting may not be uniform from one intervention to another. The record does not provide enough information to calculate or compare event rates, so the interpretation should remain tied to the stated event count definition.
In general, count outcomes can have a distribution that differs from the symmetric distributions often assumed for continuous measurements. Counts cannot fall below zero, and their variability may be larger than a simple count model expects, a feature called over-dispersion. When over-dispersion is present, a model that assumes less variability can produce uncertainty estimates that are too narrow. This is a general statistical consideration, not a claim about the data in this study. The registry record does not report a count model or information sufficient to assess over-dispersion.
What does a confidence interval add?
In general, a confidence interval expresses the uncertainty around an estimated quantity under the assumptions of the chosen method. A narrow interval indicates greater precision than a wide interval, though precision does not establish that an estimate is free from bias or that a treatment caused an outcome. The registry entries do not report a confidence interval for the primary event count. Because the outcome result itself is not reported, its precision cannot be evaluated.
For a count, the form of an interval depends on how the data are modeled and on what quantity is being estimated. An interval for a raw count is not interchangeable with an interval for a rate or a comparison between groups. The registry identifies the endpoint unit as events and describes descriptive analysis, but does not specify a time-at-risk rate, a model-based estimate, or a between-group contrast. No such quantity should be inferred from the endpoint definition alone.
Why does the design affect interpretation?
A single-group design describes outcomes among participants receiving the intervention but does not include a contemporaneous comparator. Random allocation, when used, can help balance measured and unmeasured prognostic factors across groups; this study is not listed as randomized and has no like-for-like control arm. Thus, this design cannot estimate a treatment contrast against an alternative condition. Any before-and-after symptom difference would also be vulnerable to explanations unrelated to the intervention. A single-group design can still provide descriptive safety and feasibility information, but its conclusions are narrower than those from a controlled comparison.
The primary endpoint is an operational safety measure. It does not directly quantify symptom reduction or compare the intervention with usual care. Likewise, an event count alone does not characterize duration, severity, or clinical consequences unless those features are separately reported. The registry defines the threshold for an event and notes that backup facilitators will be available, but it does not report event-level details or the observed total.
How should planning assumptions be read?
Sample-size calculations use assumptions about the planned comparison, the effect to detect, variability, and the desired error rates. The registry's planning description refers to a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It also says that the effect to detect is a stated fraction of the observed effect. These are general planning inputs; they do not show that the trial itself used a two-arm randomized design. The study is registered as single-group, with allocation not applicable.
A sample-size illustration based on an observed effect is a planning exercise, not a measure of the study's observed power. It describes the sample size that might be required under the stated assumptions for a hypothetical design. It does not establish that the observed trial had a particular probability of detecting an effect, and it cannot substitute for a treatment-effect estimate or its uncertainty. The registry record does not report the study's own sample-size justification, and it does not report a numerical primary outcome result from which to judge the observed effect.
For time-to-event calculations, a planning method may focus on the total number of events; other planning calculations may report participants per arm. That distinction is part of general sample-size methodology. It does not alter the fact that this study's registered primary endpoint is an event count in a single-group setting. No additional numerical planning result or trial-specific statistical model is reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
Multiplicity arises when researchers test or estimate several outcomes, time points, subgroups, or treatment contrasts. In general, conducting many tests can increase the chance of at least one result appearing notable by chance. Prespecified outcome priorities and statistical adjustments can help readers understand how multiple analyses were handled. The registry lists the primary count outcome and HADS change in anxiety and depression as a secondary outcome. It does not report a detailed multiplicity strategy, adjustment procedure, or a fuller statistical analysis plan. The record does not state whether additional time points or subgroup analyses were planned.
Missing-data methods also affect interpretation. A complete-case analysis, an imputation method, and a model that uses available observations make different assumptions about missingness. The registry record does not report missing-data procedures, the amount or pattern of missing outcome data, or how participants with incomplete assessments were handled. It also does not describe the analysis populations, such as whether all enrolled participants or only those who received the intervention contributed to each analysis.
The registry records enrollment as 55, while the safety reporting lists 52 at risk for serious adverse events and 52 at risk for other adverse events. The reason for these differing counts is not reported in the registry record. They should not be reconciled by assumption, and no additional participant flow can be inferred. The numerical primary-endpoint result and HADS result are also not reported in the registry record. These gaps limit assessment of outcome completeness, analysis populations, and the robustness of any statistical conclusions.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Treatment (Psilocybin, Therapy) | 3 | 52 | 5.8% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Treatment (Psilocybin, Therapy) | 2 of 52 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Treatment (Psilocybin, Therapy) | 30 of 52 |
Most frequent serious adverse event terms
| Event term | Organ system | Treatment (Psilocybin, Therapy) |
|---|---|---|
| Death | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 2 of 52 |
| dehydration | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 1 of 52 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Treatment (Psilocybin, Therapy) |
|---|---|---|
| hypertension | Cardiac disorders | 19 of 52 |
| anxiety | Nervous system disorders | 3 of 52 |
| headache | Nervous system disorders | 2 of 52 |
| nausea | Gastrointestinal disorders | 2 of 52 |
| malaise | Psychiatric disorders | 2 of 52 |
| shaking | Musculoskeletal and connective tissue disorders | 1 of 52 |
| chest tightness, muscular | Musculoskeletal and connective tissue disorders | 1 of 52 |
| migraine | Nervous system disorders | 1 of 52 |
Serious events with the highest arm-level rate: death (3.8%), dehydration (1.9%).
The registry lists 52 participants at risk for serious adverse events and 3 affected. For other adverse events, it lists 52 at risk and 30 affected. It records 2 deaths. Among serious adverse-event terms, Death is reported at 3.8% and dehydration at 1.9%. The registry record does not provide the event narratives, timing, attribution, or enough detail to determine how the terms relate to the listed death count.
“At risk” and “affected” are distinct safety-reporting concepts: the former identifies the population considered for the category, while the latter counts those reported as affected. These entries should not be added together or treated as mutually exclusive categories. A participant may experience more than one event, and the record does not specify the relationship between event terms and affected participants. The reported percentages should be read as the registry's figures; the denominator used for each term is not reported in the registry record.
These safety counts describe reports in a single-group study. Without a comparator group, they do not estimate whether an event occurred more often because of the intervention than it would have under another condition. The record also does not establish causation for any listed event. The difference between enrollment and safety denominators is not explained in the registry record, so no reason should be assigned to it.
12. What the Result Does, and Does Not, Mean
The registry documents a completed phase 1/2 study of a group model of psilocybin-assisted therapy in patients with metastatic cancer and symptoms of anxiety and/or depression. It specifies a primary outcome intended to describe distress episodes that exceed the immediate capacity of the facilitation team during the Day 0 administration session. That definition makes the endpoint relevant to group-session safety and staffing. However, the numerical result for the primary endpoint is not reported in the registry record, so the frequency of qualifying episodes cannot be described.
The record also identifies HADS change in anxiety and depression as a secondary outcome, but does not report its numerical result. Therefore, the registry information does not establish the magnitude or precision of symptom change. The design has no separate comparator group, which means that even a reported change over time would not by itself establish that the intervention caused it. A controlled comparison would be needed to estimate differences relative to a concurrent alternative condition, subject to its own design and analysis assumptions.
The safety entries indicate that serious and other adverse events were recorded, with the reported counts and serious-event terms stated in the registry. They do not, on their own, establish causal attribution or comparative safety. The registry does not provide enough detail to interpret event timing, individual circumstances, or whether reported terms overlap with the death count.
These limits do not erase the descriptive purpose of the study. A group-based phase 1/2 study can contribute information about how an intervention is delivered and what safety outcomes are monitored. But the registry entries do not give the primary event result, the HADS result, a comparator, or a detailed analysis plan. Conclusions should therefore stay within what is documented: the study's design, endpoint definitions, and reported safety entries. No claim about treatment benefit or lack of benefit follows from the missing outcome results.
13. Why This Trial Matters Statistically
This study raises a statistical question specific to delivering an intervention in groups: how often does distress reach a threshold at which one-to-one facilitator attention cannot be met by the team assigned to the session? That question connects an individual participant's experience with the operational capacity of a group intervention. Defining the event in advance makes the measure more interpretable than an unspecified count of distress, because it sets out the circumstances that qualify.
The group context also makes the observation setting important. The registry says group sizes vary and that backup facilitators will be available when the threshold is reached. Those operational details can affect how a count should be understood across sessions. A raw count is not automatically a rate or a measure of risk unless the observation opportunities and denominator are defined. The registry identifies the unit as events but does not report a rate or the primary observed count.
The design is also statistically important. A single-group phase 1/2 study can support descriptive work on an intervention model and its monitored outcomes, but it does not provide a randomized treatment contrast. The primary endpoint is about capacity and distress during administration, while HADS change is listed separately as a secondary measure of anxiety and depression. Keeping these constructs distinct prevents a safety or staffing outcome from being mistaken for an efficacy outcome.
Finally, the record illustrates why outcome definitions and numerical results both matter. The definition is detailed, but the result is not reported in the registry record. Without that result, readers cannot assess the observed frequency or its precision. Clear reporting of counts, analysis populations, missing data, and uncertainty would be needed to move from a well-defined measurement question to a fuller statistical interpretation.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The most immediate limitation of the registry information is that it does not report a numerical result for the primary outcome. Although the endpoint is carefully defined as a count of distress instances exceeding the facilitation team's capacity during the Day 0 administration session, the observed count and its uncertainty are not available in the registry record. The HADS secondary outcome is listed, but its numerical result is also not reported in the registry record.
The study has a single-group design, no masking, and no separate comparator. This limits causal interpretation and means the registry does not provide a randomized, like-for-like treatment comparison. The absence of a control group is particularly relevant if interpreting changes in anxiety or depression, which may reflect factors beyond the intervention.
The endpoint is specific to one operational threshold. It does not, as defined, capture every form of distress, the duration or severity of an episode, or a broader clinical outcome. Group sizes vary, and the record does not report the number or size of groups, the total observation exposure, or a rate calculation. It also does not explain how an event was recorded across sessions or whether repeated events involving a participant were distinguished in any particular way.
Other information needed for a fuller statistical appraisal is not reported in the registry record: the detailed analysis plan, sample-size justification, missing-data handling, analysis populations, confidence intervals, and the reason enrollment and safety denominators differ. Safety entries do not include narratives or attribution details. These limits constrain interpretation of both outcome completeness and the relationship between reported adverse events and the intervention.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Psilocybin-Assisted Therapy for the Treatment of Cancer-Related Anxiety in Patients With Metastatic Cancer — NCT05847686.
- Registry record last updated 2025-11-05; status last verified 2025-10.
- Results first posted 2025-04-30.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry record describes NCT05847686, a completed phase 1/2, single-group study sponsored by the University of Washington. It lists enrollment as 55 and dates the study start to 2023-06-27 and primary completion to 2024-04-08. Participants in the treatment group received psilocybin by mouth and participated in group and individual therapy.
The primary endpoint is the number of Day 0 instances of distress requiring one-to-one facilitator attention beyond the four-person facilitation team's capacity. HADS change in anxiety and depression is listed as a secondary outcome. Numerical results for these outcomes are not reported in the registry record.
The safety record lists 52 at risk and 3 affected for serious adverse events, 52 at risk and 30 affected for other adverse events, and 2 deaths. Serious-event terms include Death at 3.8% and dehydration at 1.9%. The record has no comparator group, and it does not report a detailed statistical plan, missing-data methods, or the reason for the safety denominators.