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 A Retrospective Effectiveness Trial of Ketamine-Assisted Psychotherapy in Adult Patients Coping With Mental Health (NCT05604794), a na phase 4 study. The primary outcome is 9-item Patient Health Questionnaire (PHQ-9).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05604794 |
| Phase | Phase 4 |
| Condition | Depression, Anxiety, Post Traumatic Stress Disorder |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 1806 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Field Trip Health |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned adult clients coping with symptoms of depression, anxiety, and post-traumatic stress at Field Trip Health centres in North America. The registry record lists an enrollment of 1806. It does not report how many participants contributed data to the primary outcome after attrition, or how participants were selected for the retrospective review.
Intervention
The intervention was Ketamine-Assisted Psychotherapy, described as a combination of ketamine and psychotherapy. This was a review of a care program rather than a randomized assignment to treatment. Details such as the specific treatment schedule, ketamine administration, psychotherapy approach, and whether these varied among clients are not reported in the registry record.
Comparator
The registry describes a single group and does not list a separate comparison group. Thus, the central comparison is within clients over time, using baseline and follow-up scores, rather than a contrast between treatment and control groups. Without a concurrent comparison group, changes cannot be separated from other influences on symptoms over the same period.
Primary question
The primary outcome is the PHQ-9, a self-reported depression measure. The registry describes the comparison as change at 3 months relative to baseline and states that higher scores are worse. The study summary says the investigators predicted lasting reductions in psychological distress, including depression, anxiety, and post-traumatic stress, detectable up to 6 months after treatment. That is a stated prediction, not a reported finding. The numerical primary outcome estimate and its confidence interval are not reported in the registry record, so the direction, size, and precision of any change cannot be evaluated from that record.
3. Trial Design
This is a completed, retrospective review of a Ketamine-Assisted Psychotherapy program at Field Trip Health centres in North America. The registry lists the study as Phase 4, with a single-group model, no masking, and allocation recorded as not applicable. It describes one group of clients rather than a randomized comparison between intervention and control arms. The registry enrollment is 1806.
The study period is recorded as starting on 2020-03-13, with primary completion on 2022-06-16. The registry status is completed. These dates describe the study record; they do not establish when each client received treatment or completed an assessment. Participant-level timing and the exact assessment schedule beyond the primary outcome description are not reported in the registry record.
The intervention is named Ketamine-Assisted Psychotherapy and classified as a combination product. The record does not give details about treatment dose, number or timing of sessions, psychotherapy content, or variation in care. Because the review is retrospective and has no separate control group, its structure is suited to describing recorded changes over time but cannot by itself isolate the effect of treatment from changes that might have occurred for other reasons.
The registry lists PHQ-9, GAD-7, and PCL-6 measures among the secondary outcomes, with entries repeated in the outcome list. It records nine outcome measures and zero analyses, but does not provide numerical results for the primary endpoint in the information available for this analysis. The sample-size illustrations use assumptions stated for planning calculations; those are not the study's original design justification, which is not reported in the registry record.
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 | Clients |
|---|---|
| STARTED | 1806 |
| COMPLETED | 94 |
| NOT COMPLETED | 1712 |
Analysis population for the primary outcome, as defined in the registry: Number analysed after attrition.
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 | Clients |
|---|---|---|
| Participants analysed | 1806 | |
| Age, Continuous | years | 42 (SD 12) |
| Sex/Gender, Customized: Gender – Female | Participants | 948 |
| Sex/Gender, Customized: Gender – Male | Participants | 850 |
| Sex/Gender, Customized: Gender – Non-binary | Participants | 8 |
| Race/Ethnicity, Customized: Race/Ethnicity – White | Participants | 1309 |
| Race/Ethnicity, Customized: Race/Ethnicity – Other Groups | Participants | 441 |
| Race/Ethnicity, Customized: Race/Ethnicity – Missing | Participants | 56 |
| Region of Enrollment: North America | Participants | 1806 |
6. Primary Endpoint
The registry lists the primary outcome as 9-item Patient Health Questionnaire (PHQ-9), measured over Change from 3 months compared to baseline.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | units on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the mean on the 9-item Patient Health Questionnaire, or PHQ-9. This is a self-reported measure of depression with a possible range from 0-27; higher scores indicate worse symptoms. Self-report measures can capture a participant's own assessment of symptoms, which makes them useful for studying changes that may not be fully represented by clinical records alone. Scores are still measurements rather than direct observations of every aspect of a person's mental health.
The registry describes the primary timeframe as change from 3 months compared to baseline. A change score expresses how the measure differs between assessments; interpreting it depends on knowing the direction used and the values at the relevant time points. The registry also states that the population is the number analysed after attrition. That wording makes the analysed population important, because participants without follow-up scores may not contribute to a change estimate. The number analysed and the numerical mean change are not reported in the registry record.
The outcome is described as a mean with a 95% confidence interval. A mean gives an average score or average change for the analysed group, while the interval conveys statistical uncertainty around the estimate. Neither the mean change nor its confidence interval is reported in the registry record. Consequently, the endpoint definition is available, but the magnitude and precision of the measured change are not.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record defines a primary outcome but does not report its numerical result. It names the PHQ-9, specifies a mean and 95% confidence interval, and describes the assessment as change at 3 months compared with baseline. However, the mean change, confidence interval limits, and number analysed are not reported in the registry record. Without these quantities, it is not possible to determine whether the posted primary estimate indicates a decrease or increase, how large any change was, or how precisely it was estimated.
The study summary says that the investigators predicted lasting reductions in psychological distress, with changes detectable up to 6 months after treatment. A prediction is not evidence that the predicted pattern occurred. No numerical outcome findings for depression, anxiety, or post-traumatic stress are included in the record information used for this interpretation. The registry lists PHQ-9, GAD-7, and PCL-6 as outcome measures, but the listed measures alone do not establish observed changes.
The design also limits what a before-and-after pattern could establish, even if numerical results were available. The registry describes a retrospective, single-group review without a separate comparison group. Symptoms can change over time for reasons other than the intervention, including natural fluctuation, concurrent care, changes in circumstances, and differences in who completes follow-up. A within-group change therefore describes the trajectory among those measured; it does not by itself identify what would have happened to the same clients without the program.
Precision matters separately from the direction or size of an estimate. A confidence interval is a range of values compatible with the data and the statistical model, and its width indicates uncertainty. Since the interval is not reported, the precision of the primary estimate cannot be judged. No conclusion about statistical significance can be drawn from the outcome definition alone.
The recorded enrollment of 1806 describes enrollment, not necessarily the number with complete primary outcome data. The primary population is described as the number analysed after attrition, but that count is absent. Thus, neither enrollment nor the study's completed status fills the gap in outcome reporting. The registry record supports a description of the study's question and design, but not a quantitative conclusion about the observed effect or its precision.
9. Statistical Methods Explained
The methods can be understood by separating the outcome definition, the comparison over time, and the uncertainty around an estimate. The primary measure is a continuous score: PHQ-9 values can vary across a scale, rather than placing each client into only a yes-or-no category. The registry specifies a mean as the summary measure. In general, a mean describes the average value in the group being analysed, but it can be influenced by unusually high or low scores. The registry record does not report the actual scores or the resulting mean change.
What does a change score represent?
A change score compares measurements at different times for the same outcome. Here, the primary timeframe is described as change at 3 months compared with baseline. A within-person comparison can account for the fact that each client has an initial score of their own, but it does not create a control group. An average change describes the measured group's trajectory. It does not tell whether that trajectory differs from what would have occurred over the same period without the program.
Interpretation also depends on the sign convention. A decrease in PHQ-9 is in the direction of fewer reported symptoms because higher scores are worse, but the record does not report the numerical estimate or explicitly state a sign convention for the change. It is therefore not possible to determine the direction of the primary result from the endpoint definition. The mean is also not a description of every participant's experience; individuals can have changes that differ from the group average.
What does a confidence interval add?
A confidence interval communicates uncertainty in an estimated quantity. In general, an interval that is narrower indicates greater precision under the model used, while a wider interval indicates less precision. The interval is not a guarantee about where an individual participant's score will fall, nor does it show the range of individual changes. The registry specifies a 95% confidence interval for the mean, but its endpoints are not reported in the registry record. The interval's width, its position relative to no change, and the estimate's precision therefore cannot be assessed.
A confidence interval is only as informative as the data and assumptions used to construct it. In a repeated-measures outcome, the availability of paired measurements matters because a change can only be calculated for participants with relevant assessments. Attrition can make the analysed group differ from the enrolled group. The record identifies the primary population as the number analysed after attrition, but does not report that number, the missingness pattern, or the method used to handle missing observations.
Why is a single-group design important?
The registry describes a retrospective single-group study with allocation not applicable and no masking. There is no listed control arm against which to compare the clients' changes. A comparison with baseline can show whether scores changed among the clients with available measurements, but secular trends, regression to the mean, concurrent treatments, selection into care, and selective follow-up are possible alternative explanations. These are general concerns for before-and-after observational evaluations; the record does not say whether or how the study addressed each one.
Retrospective reviews use information collected in routine settings or for purposes other than a prospectively assigned experimental comparison. This can make such studies informative about recorded clinical experience, but the completeness and consistency of records can affect estimates. The registry does not report the extraction procedures, data validation, eligibility rules for the retrospective cohort, or adjustment methods. Those details should not be inferred.
How should planning illustrations be read?
Sample-size illustrations are planning calculations, not evidence that the study had a particular probability of finding an effect. The stated illustration assumptions include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the target effect is a stated fraction of the observed effect. These assumptions describe hypothetical planning rather than the original retrospective single-group design. The registry does not report the study's own sample-size justification, and illustrations based on an observed effect should not be called observed power.
For continuous outcomes, planning calculations depend on the target difference and variability assumptions, among other design choices. If an illustration describes participants per arm for 80% power, it refers to a hypothetical two-arm design under its assumptions, not the number actually analysed in this single-group review. The available record does not give numerical outcome estimates with which to assess such calculations. No planning illustration can substitute for reporting the observed mean change, confidence interval, and analysed population.
Finally, the registry records zero analyses. That does not establish that no analysis was performed outside the registry; it means analyses are not recorded in the information. In the absence of a reported statistical analysis plan, the selected model, covariates, handling of repeated measurements, and any sensitivity analyses are not reported in the registry record. General statistical principles can explain what such methods would do, but cannot identify which methods were used in this study.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists PHQ-9, GAD-7, and PCL-6 among secondary outcomes, with repeated entries for each measure, and records nine outcome measures. It does not report a multiplicity strategy, such as a prespecified hierarchy of outcomes or an adjustment for testing multiple outcomes. When many outcomes or time points are examined, the chance of at least one apparently unusual result can increase. This is a general reason to interpret isolated findings cautiously; it is not evidence that any particular analysis in this study was or was not adjusted.
The registry records zero analyses and does not provide an analysis plan or numerical outcome results. The statistical tests, models, covariate adjustments, and any planned subgroup or sensitivity analyses are not reported in the registry record. It is also not reported whether the repeated outcome entries represent different assessments, populations, or other distinctions.
The primary outcome population is described as the number analysed after attrition, but the analysed number, the extent of missing follow-up, and reasons for missingness are not reported. Missing data can affect a change estimate if participants with absent follow-up differ from those with observed follow-up. Methods such as complete-case analysis or imputation make different assumptions; the registry does not identify which, if any, were used. The enrollment count cannot be treated as the primary endpoint denominator without a reported analysed count. Accordingly, the completeness and representativeness of the endpoint data cannot be assessed from the registry record.
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 |
|---|---|---|---|
| Clients | 0 | 1806 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Clients | 0 of 1806 |
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 |
|---|---|
| Clients | 0 of 1806 |
The adverse-event record lists the Clients group with 1806 at risk for serious adverse events and 0 affected. It also lists 1806 at risk for other adverse events and 0 affected, and records 0 deaths. These are registry counts for the categories recorded; they do not give event descriptions because no serious-event terms are listed.
A count of zero recorded affected participants should be read as a feature of the reported record, not as proof that no adverse events occurred in the broader care setting. The record does not provide information on how events were sought, the reporting window, severity definitions, completeness of reporting, or whether events were independently reviewed. It also does not report exposure duration for individuals.
The at-risk counts are not a measure of the number with complete symptom assessments. Nor do these counts provide a comparison with an untreated or alternative-treatment group. The safety entries therefore describe what was recorded for this single group, while leaving the ascertainment and interpretation context unclear. They should not be used to infer a treatment's safety profile beyond the limits of the recorded counts.
12. What the Result Does, and Does Not, Mean
The record establishes that Field Trip Health conducted a completed retrospective review of a Ketamine-Assisted Psychotherapy program in adult clients coping with symptoms of depression, anxiety, and post-traumatic stress. It defines the primary outcome as mean PHQ-9 change at 3 months compared with baseline and states that higher PHQ-9 scores are worse. It also lists GAD-7 and PCL-6 measures and records adverse-event counts.
Those design and measurement details do not establish what happened to participants' scores. The numerical primary estimate, confidence interval, and number analysed are not reported in the registry record. Numerical results for the listed secondary outcomes are also not reported in the available record information. Consequently, the direction, magnitude, and precision of symptom change cannot be described. The study summary's prediction of lasting reductions is an expectation stated by the investigators, not a result.
Even if a within-group improvement were reported, a retrospective single-group design would not establish that the program caused the change. Other influences over time, selection into treatment, concurrent care, attrition, and measurement processes can contribute to observed patterns. A comparison group and a clear account of the analysis can help address some questions, but neither is described in this record.
The adverse-event entries record zero affected participants for serious events and other events, and zero deaths. These counts are not a comprehensive guarantee about all possible events, because ascertainment and follow-up details are not reported. The record's value is therefore primarily in identifying the program, population, design, outcome definitions, and recorded safety counts. It does not support a quantitative conclusion about effectiveness or a broad causal or safety claim.
13. Why This Trial Matters Statistically
This study is statistically notable for the question it asks in a real-world care setting and for the design used to address it. A retrospective review can describe outcomes recorded among clients receiving a program, while a single-group structure makes the interpretation of change fundamentally different from a randomized treatment comparison. The distinction matters: a before-and-after estimate, if reported, would characterize change in the observed group but would not by itself estimate the causal effect of the program.
The primary endpoint is defined in clinically interpretable terms: a self-reported depression measure with higher scores indicating worse symptoms, evaluated as change from baseline at 3 months. The record also identifies anxiety and post-traumatic stress measures. This creates a clear measurement framework, but the absence of numerical estimates and analysed counts prevents readers from judging either the observed pattern or its precision.
The registry status is completed, yet completion status is not equivalent to complete outcome reporting. Enrollment does not establish how many participants had follow-up scores, and the primary population is explicitly described as the number analysed after attrition. Reporting the analysed population and the handling of missing data is important because estimates based only on available follow-up can be difficult to generalize if follow-up is selective.
The record also illustrates why planning calculations must be kept distinct from study results. The stated sample-size assumptions describe planning illustrations for a hypothetical two-arm design, whereas the recorded study is single-group and retrospective. Such illustrations can show how design assumptions relate to sample size, but they cannot retroactively justify the study design or establish observed power. The statistical contribution of the record is thus chiefly its explicit design and endpoint description, alongside important gaps in result and analysis reporting.
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 for interpreting the study is that the registry record does not report the numerical primary outcome estimate, its 95% confidence interval, or the number analysed. Without these details, neither the direction nor the size and precision of the primary change can be assessed. Numerical results for the listed secondary measures are also not reported in the available record information.
The design is retrospective and single-group, with no separate comparison group. This prevents a direct comparison against what might have happened over the same period without the intervention. The record does not describe adjustment for potential confounding, concurrent treatments, or other influences on symptoms. Such factors may matter in an observational before-and-after review, but whether they were measured or addressed is not reported.
Attrition is relevant because the primary population is described as the number analysed after attrition. The number with outcome data, the amount and pattern of missingness, and the method used to handle missing data are not reported in the registry record. These omissions limit assessment of whether the measured group represents the enrolled group.
Additional information about the retrospective cohort is not reported, including detailed eligibility criteria, the extraction process, treatment delivery, and the timing of individual assessments. The registry lists nine outcome measures and repeated outcome labels, but does not explain their distinctions or report a multiplicity approach. The adverse-event counts are recorded without details about ascertainment, follow-up, or event definitions. Finally, the study summary's anticipated follow-up to 6 months does not provide observed results at that time. These limitations mean the record describes a research question and program review, but does not permit a robust quantitative interpretation of outcomes.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Retrospective Effectiveness Trial of Ketamine-Assisted Psychotherapy in Adult Patients Coping With Mental Health — NCT05604794.
- Registry record last updated 2024-03-20; status last verified 2024-02.
- Results first posted 2023-05-12.
- 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.
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18. Record Summary
NCT05604794 is a completed Phase 4 retrospective review of Ketamine-Assisted Psychotherapy at Field Trip Health centres in North America. The registry describes a single group, no masking, allocation not applicable, and enrollment of 1806. The study start is recorded as 2020-03-13 and primary completion as 2022-06-16.
The primary outcome is mean PHQ-9 change at 3 months compared with baseline, with a 95% confidence interval specified. The record also lists GAD-7 and PCL-6 measures. Numerical outcome results, the primary analysed count, and the analysis methods are not reported in the registry record. Adverse-event entries record 0 affected participants for serious events, 0 for other events, and 0 deaths, with ascertainment details not reported.