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 Trial of Dronabinol Adjunctive Treatment of Agitation in Alzheimer's Disease (NCT02792257), a randomized phase 2 study. The primary outcome is Symptoms of Agitation as Measured by the Pittsburgh Agitation Scale.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02792257 |
| Phase | Phase 2 |
| Condition | Alzheimer's Disease |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 84 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Johns Hopkins University |
| Results posted | Yes |
2. Clinical Question
Population
People with Alzheimer’s disease and agitation are the intended population described in the registry summary. The summary describes agitation as including behaviors such as combativeness, yelling, pacing, lack of cooperation with care, insomnia, and restlessness. The specific eligibility criteria and the characteristics of participants enrolled are not reported in the registry record.
Intervention
The intervention was dronabinol used as adjunctive treatment. Capsules were administered twice daily. The recorded regimen was 2.5 mg per dose (5mg daily) during Week 1, followed by 5 mg per dose (10mg daily) for Weeks 2 and 3.
Comparator
The comparator was placebo medication, administered twice daily. Other details about background care or whether it was standardized between groups are not reported in the registry record.
Primary question
The primary endpoint was agitation severity measured with the Pittsburgh Agitation Scale (PAS) over up to 3 weeks. The statistical question is whether the recorded PAS outcome differed between the randomized dronabinol and placebo groups. The primary-outcome comparison itself is not reported in the registry record, so its size and precision cannot be described.
The clinical rationale in the registry summary is the burden associated with agitation in Alzheimer’s disease and the need for interventions directed at this symptom. That rationale explains the question being studied; it is not evidence of benefit or harm. The posted information supports describing the trial’s intended comparison and measurement, but not drawing a conclusion about the relative effect of the treatments.
3. Trial Design
This was a Phase 2 randomized, parallel-group trial comparing dronabinol with placebo. The registry lists an enrollment of 84 and the status as completed. Enrollment is the trial-level registry figure; it does not establish how many participants were analyzed for any particular outcome. The sponsor was Johns Hopkins University.
The trial was quadruple-masked according to the registry. This describes the recorded masking designation, but the registry information does not identify which roles were masked or explain how masking was maintained. Allocation was randomized. Details such as the randomization procedure, allocation concealment, and any stratification factors are not reported in the registry record.
The recorded start date is 2017-03-01, and the primary completion date is 2024-05-31. The trial is described as a pilot trial in its official title. The record’s schedule specifies twice-daily administration for both groups. Dronabinol dosing began at 2.5 mg per dose (5mg daily) during Week 1, then increased to 5 mg per dose (10mg daily) for Weeks 2 and 3. Placebo was administered twice daily; further details of its schedule are not reported.
The design identifies a controlled comparison over a short treatment period, with agitation severity as the primary outcome and adverse events as a secondary safety outcome. The registry does not report the detailed protocol, eligibility criteria, adherence information, concomitant treatments, or the planned statistical analysis. Those omissions prevent a fuller assessment of how the study was conducted and how the reported outcomes were intended to be analyzed.
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.
Before assignment: 84 subjects signed consents to be screened for eligibility. 9 participants signed consents but did not meet the eligibility criteria to start the study (screen failures). 75 subjects were randomized to treatment groups in the study.
Overall Study
| Stage | Dronabinol | Placebo |
|---|---|---|
| STARTED | 37 | 38 |
| COMPLETED | 32 | 31 |
| NOT COMPLETED | 5 | 7 |
Reasons for not completing this period:
| Reason | Dronabinol | Placebo |
|---|---|---|
| Lost to Follow-up | 3 | 4 |
| Allergy | 0 | 1 |
| Protocol Violation | 2 | 0 |
| Excessive Agitation | 0 | 1 |
| Not Feeling Well | 0 | 1 |
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 | Dronabinol | Placebo | Total |
|---|---|---|---|---|
| Participants analysed | 37 | 38 | 75 | |
| Age, Customized: Mean Age | years | 79.1 (SD 7.3) | 77.9 (SD 7.7) | 78.5 (SD 7.5) |
| Sex: Female, Male: Female | Participants | 22 | 27 | 49 |
| Sex: Female, Male: Male | Participants | 15 | 11 | 26 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 4 | 4 | 8 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 33 | 34 | 67 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 1 | 1 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 2 | 5 | 7 |
| Race (NIH/OMB): White | Participants | 35 | 32 | 67 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Education | years | 14.1 (SD 2.9) | 13.6 (SD 3.6) | 13.8 (SD 3.2) |
| Current Antidepressant: Yes | Participants | 7 | 25 | 32 |
| Current Antidepressant: No | Participants | 30 | 13 | 43 |
| Current Antipsychotic: Yes | Participants | 20 | 18 | 38 |
| Current Antipsychotic: No | Participants | 17 | 20 | 37 |
| NPI-C Agitation/Aggression | units on a scale | 21.9 (SD 9.7) | 19.0 (SD 11.2) | 20.4 (SD 10.5) |
| NPI-C Sleep | units on a scale | 3.3 (SD 5.1) | 3.6 (SD 4.9) | 3.5 (SD 5.0) |
| NPI-C Disinhibition | units on a scale | 7.4 (SD 7.3) | 5.8 (SD 7.0) | 6.6 (SD 7.1) |
| NPI-C Irritability | units on a scale | 10.3 (SD 7.6) | 10.3 (SD 9.9) | 10.3 (SD 8.8) |
| Activities of Daily Living (ADL) Checklist | units on a scale | 25.4 (SD 20.3) | 21.1 (SD 19.2) | 23.2 (SD 19.8) |
| Mini Mental State Examination (MMSE) | units on a scale | 9.1 (SD 7.8) | 8.2 (SD 5.7) | 8.6 (SD 6.8) |
| Severe Impairment Battery (SIB) | units on a scale | 11.9 (SD 7.4) | 12.6 (SD 6.3) | 12.3 (SD 6.8) |
6. Primary Endpoint
The registry lists the primary outcome as Symptoms of Agitation as Measured by the Pittsburgh Agitation Scale, measured over Up to 3 weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | score on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was symptoms of agitation measured by the Pittsburgh Agitation Scale (PAS), recorded as a score on a scale. The registry describes the PAS as a tool for assessing agitation severity in people with dementia. Its minimum score is 0 and its maximum score is 16; higher scores indicate a worse outcome, meaning more agitation.
A scale-based measure can capture variation in symptom severity rather than reducing the outcome to whether agitation is present or absent. In general, a continuous score may be summarized using a mean and standard deviation, as the registry identifies for this endpoint. The mean describes the average score in a group, while the standard deviation describes how dispersed individual scores are around that average. Neither summary alone establishes the difference between randomized groups or how precisely that difference is estimated.
The recorded timeframe is up to 3 weeks. That window indicates the period attached to the endpoint in the registry, but the exact assessment schedule and the choice of assessment used for any primary comparison are not reported in the registry record. The registry information does not give group means, standard deviations, an estimated treatment contrast, a confidence interval, or a p-value for the primary outcome. Consequently, the direction, magnitude, and precision of any difference in PAS scores cannot be determined from the recorded primary-outcome information.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies agitation severity on the PAS as the primary outcome, but does not report a single primary-outcome comparison. In particular, no group-level PAS means or standard deviations, estimated difference, confidence interval, or p-value are stated in the registry record. Without an effect estimate and its uncertainty, the treatment groups cannot be compared quantitatively on this endpoint. The available record therefore does not establish the direction or size of a difference in agitation scores.
The outcome information also does not resolve whether any observed change would be clinically important. Statistical interpretation would ordinarily consider the estimated difference, its uncertainty, the scale’s direction, and the clinical context. Here, the scale direction is clear: a higher PAS score means worse agitation. But the record does not give the group results needed to apply that interpretation. It would be inappropriate to infer a result from the trial’s rationale, title, completion status, or planned dosing.
The registry lists adverse-event counts separately. For serious adverse events, it records 2 affected participants among 37 at risk in the dronabinol group and 0 among 38 at risk in the placebo group. It also records other adverse events in both groups. These are descriptive safety counts, not a substitute for the missing primary-outcome comparison. The record does not provide a statistical comparison or uncertainty estimate for these safety figures, so they should not be treated as proof of a difference between groups.
The primary outcome is recorded as a mean of a continuous measure, while the registry indicates that the primary outcome has several categories or time points and has not been reduced to one comparison. That distinction matters: a single summary may not capture every assessment, and choosing among multiple time points or categories can affect interpretation. The exact set of primary assessments, the analysis population, the missing-data approach, and the prespecified contrast are not reported in the registry record.
Any planning illustration based on an observed effect has a different purpose from a trial result. It describes a hypothetical future design under stated assumptions, rather than the probability that this completed trial detected an effect. It cannot fill in the missing estimate or provide evidence that the intervention changed agitation. The central statistical conclusion is therefore limited: the registry describes a randomized comparison and its intended primary measure, but does not report a usable primary treatment-effect estimate.
9. Statistical Methods Explained
The registry describes a randomized parallel-group comparison and identifies a continuous primary measure summarized by a mean and standard deviation. It does not report a single primary-outcome comparison or the detailed statistical analysis used. The following explanations are general statistical guidance for interpreting this type of study; they do not describe analyses that the registry confirms were performed.
What does a mean and standard deviation describe?
In general, the mean is the arithmetic average of the observed scores in a group. The standard deviation describes how widely scores vary around that average. For a scale where higher values represent worse symptoms, a group mean gives a concise account of average symptom severity, while the standard deviation gives context about the spread of individual scores. A mean difference between groups would express the average contrast on the scale’s original units. The registry does not report group means or a mean difference for the PAS outcome.
A group average does not show every participant’s experience, and a standard deviation is not the uncertainty around the group mean. Uncertainty in an estimated treatment contrast is commonly expressed by a confidence interval. In general, a confidence interval gives a range of values reasonably compatible with the data and analysis assumptions. Its width reflects precision: a wider interval indicates greater uncertainty. No primary-outcome confidence interval is reported in the registry record.
What does a p-value answer?
In general, a p-value assesses how compatible the observed data are with a specified null hypothesis under the analysis assumptions. It does not give the probability that the null hypothesis is true, and it does not measure the clinical importance of an effect. A small p-value alone would not show whether a difference is large enough to matter; a large p-value would not establish that the treatments are equivalent. The registry record does not report a primary-outcome p-value, and it does not report the primary statistical test.
Why can repeated assessments complicate analysis?
Agitation can be measured at multiple assessments, and the registry flags the primary outcome as having several categories or time points rather than one reduced comparison. In general, observations from the same participant over time are related, not independent. An analysis that uses repeated measurements should account for that within-participant relationship and should define how time and treatment are compared. If several assessments or outcome categories are examined, the analysis also needs a clear approach to interpreting the resulting comparisons. The precise PAS assessment schedule and statistical model are not reported in the registry record.
What do the planning assumptions mean?
The registry describes planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It says the effect to detect is expressed as a stated fraction of the observed effect. These are planning assumptions, not evidence about the probability that the completed trial detected a treatment effect. Sample-size illustrations are hypothetical design quantities; they are not observed power. The registry does not report that these assumptions formed the trial’s original design or sample-size justification.
In general, a two-sided significance level sets the analysis threshold for considering results inconsistent with the null in either direction. Equal allocation means a hypothetical design assigns the same planned number of participants to each group. A normal approximation uses a mathematical approximation to describe the sampling behavior of an estimate. Each assumption affects a planning calculation, and the calculation should not be mistaken for an observed clinical result. The registry explicitly distinguishes these illustrations from the trial’s own design.
Why does over-dispersion matter in general?
Over-dispersion is a general issue for some count-data analyses: the observed variability can exceed what a chosen statistical model expects. If a model does not accommodate that extra variability, standard errors may be too small and confidence intervals may be too narrow. The primary endpoint in this trial is described as a continuous PAS score, not a count outcome, and the registry does not say that an over-dispersed model was used. This concept should therefore not be read as a feature of the trial’s reported primary analysis.
For adverse-event counts, interpretation also depends on the definitions of events, the time at risk, and the method used to compare groups. The registry provides counts and at-risk figures but does not report a statistical model, confidence intervals, or a formal comparison for these outcomes. Descriptive counts alone do not establish a causal effect or quantify uncertainty.
Overall, the registry supports explaining the endpoint and the stated planning assumptions, but it does not provide enough information to reconstruct a primary analysis. The exact model, covariates, handling of repeated measures, statistical test, confidence interval method, and any adjustments are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry identifies 3 outcome measures and 3 analyses, and it flags the primary outcome as having several categories or time points rather than being reduced to one comparison. That leaves important interpretive questions unresolved. The registry record does not report how the primary comparison was selected from the different assessments, whether a particular time point was designated as primary for analysis, or whether any multiplicity adjustment was planned or performed.
In general, examining several outcomes or time points can increase the chance of finding an apparently unusual result by chance. A prespecified hierarchy, adjustment, or clear distinction between primary and exploratory analyses can help readers understand how to interpret multiple comparisons. The registry information does not describe such a strategy, so it is not possible to determine how multiplicity was handled.
The registry record does not report the amount or pattern of missing primary-outcome data, reasons for missing assessments, or the method used to handle missing values. It also does not report whether analyses used all randomized participants, participants with available measurements, or another analysis population. These details matter because missingness and analysis-population choices can affect the estimate and its uncertainty.
There is no reported account of sensitivity analyses assessing how conclusions might change under different assumptions about missing data. That absence should not be interpreted as evidence that data were complete or that a particular method was used. The record does not report interim analyses, stopping rules, or a statistical plan for these issues. Without these details and without a primary-outcome estimate, the robustness of a treatment-effect conclusion cannot be assessed.
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 |
|---|---|---|---|
| Dronabinol | 2 | 37 | 5.4% |
| Placebo | 0 | 38 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Dronabinol | 0 of 37 |
| Placebo | 0 of 38 |
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 |
|---|---|
| Dronabinol | 21 of 37 |
| Placebo | 20 of 38 |
Most frequent serious adverse event terms
| Event term | Organ system | Dronabinol | Placebo |
|---|---|---|---|
| Delirium | Psychiatric disorders | 1 of 37 | 0 of 38 |
| Humeral Fracture | Surgical and medical procedures | 1 of 37 | 0 of 38 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Dronabinol | Placebo |
|---|---|---|---|
| Fall | General disorders | 3 of 37 | 5 of 38 |
| Somnolence | Nervous system disorders | 2 of 37 | 5 of 38 |
| Diarrhea | Gastrointestinal disorders | 5 of 37 | 0 of 38 |
| Confusion | Psychiatric disorders | 3 of 37 | 2 of 38 |
| Agitation | Psychiatric disorders | 2 of 37 | 2 of 38 |
| Delirium | Psychiatric disorders | 1 of 37 | 2 of 38 |
| UTI | Renal and urinary disorders | 1 of 37 | 1 of 38 |
| Dysarthria | Nervous system disorders | 1 of 37 | 1 of 38 |
| Insomnia | Psychiatric disorders | 0 of 37 | 2 of 38 |
| Hypotension | Vascular disorders | 1 of 37 | 1 of 38 |
Serious events with the highest arm-level rate: delirium (2.7%), humeral fracture (2.7%).
The registry records serious adverse events for the two groups separately. In the dronabinol group, 2 participants were recorded as affected among 37 at risk; in the placebo group, 0 were recorded as affected among 38 at risk. Deaths are recorded as 0 in each group. These figures are descriptive counts as listed in the registry, not estimates of a comparative treatment effect.
The record also lists other adverse events: 21 affected among 37 at risk in the dronabinol group and 20 among 38 at risk in the placebo group. The registry does not provide a statistical comparison, confidence interval, or details about event severity or timing for these figures. They therefore should not be read as establishing whether the groups differed in safety.
The listed serious adverse-event terms are Delirium and Humeral Fracture, each recorded as 2.7%. The registry information does not establish how those terms map to individual participants or provide a fuller account of timing and attribution. Serious-event counts can be sparse, and small counts offer limited precision. In general, such figures are best read as a description of events recorded during the trial, not as proof that a treatment caused or prevented an event.
12. What the Result Does, and Does Not, Mean
The trial record answers some design questions clearly: it describes a randomized, quadruple-masked, parallel-group Phase 2 comparison of adjunctive dronabinol with placebo, and identifies PAS agitation severity as the primary endpoint. It also specifies a treatment schedule and a primary-outcome timeframe of up to 3 weeks. These details define the question the trial was intended to address.
What the registry record does not provide is the primary result needed to answer that question quantitatively. There is no reported group-level PAS summary or single treatment contrast, and no uncertainty estimate or p-value. The posted information therefore cannot establish whether PAS scores were higher or lower in either group, how large any difference was, or how precise an estimate might be.
The safety counts describe adverse events recorded in the groups, but do not, on their own, establish a causal relationship or a statistically reliable difference. The serious-event counts are limited, and the record does not give comparative uncertainty estimates or detailed event context. Likewise, the listed terms and percentages do not replace a complete safety analysis.
The pilot designation does not itself determine whether a result is conclusive or inconclusive. In general, pilot studies can inform feasibility and future research, but conclusions depend on the study’s aims, conduct, and reported estimates. The registry does not report a sample-size justification for the trial’s original design, and planning illustrations based on observed effects should not be confused with a test of efficacy or observed power.
Accordingly, the registry supports a description of the randomized question and recorded safety counts, but not a conclusion about whether dronabinol changed agitation or whether the observed differences were clinically important. The missing primary comparison, analysis details, and precision estimates place a firm limit on what can be inferred.
13. Why This Trial Matters Statistically
This trial is statistically notable because it targets a behavioral symptom using a scale-based primary measure. The PAS is recorded as a continuous score with a defined direction: higher values mean worse agitation. That makes the choice and interpretation of a between-group summary important. A mean difference, accompanied by an uncertainty interval, would ordinarily help describe the magnitude and precision of the contrast on the scale.
The registry record also illustrates why trial design information and trial results must be kept distinct. Randomization and masking describe features intended to support a fair comparison, but they do not substitute for outcome estimates. Similarly, completion status and enrollment do not establish that a treatment effect was demonstrated. The primary outcome’s several categories or time points make clear reporting of the prespecified comparison especially important.
The planning illustrations have a separate statistical role. Under the stated assumptions, they can inform hypothetical future study design, but they are not a measure of what the completed trial actually established. A planning calculation based on an observed effect is especially dependent on the selected effect size and assumptions; it cannot be used to recover an unreported result.
The adverse-event figures also show the limits of descriptive safety data. Counts offer a straightforward account of recorded events, but without comparative estimates and uncertainty they cannot establish the size or reliability of a group difference. The registry’s reporting of serious events alongside other adverse events makes it important to distinguish event categories rather than collapse them into a single interpretation.
Most importantly, statistical transparency depends on reporting the outcome estimate, its precision, and the analysis choices. Those details are not reported for the primary endpoint in the registry record. The result is a clearly described research question, but an incomplete basis for assessing the primary statistical evidence.
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 main trial-specific limitation for interpretation is that the registry record does not report a single primary-outcome comparison. It gives the PAS definition and direction but no group summaries, effect estimate, confidence interval, or p-value. Consequently, the primary question cannot be answered from the recorded outcome information.
The registry flags multiple categories or time points for the primary outcome, yet the specific assessment schedule and the method for selecting or combining assessments are not reported. The record also does not report the statistical model, adjustment variables, analysis population, or handling of repeated measurements. These omissions make it impossible to assess whether the analysis aligned with the randomized design and the endpoint structure.
Participant flow and outcome completeness are not described in the registry information. The enrollment figure does not indicate how many participants contributed data to each analysis. Reasons for missing measurements, adherence to the dosing schedule, and concomitant treatment details are not reported. These factors could affect interpretation, but their influence cannot be evaluated from the registry record.
The safety information is similarly limited to recorded counts, at-risk figures, and listed serious-event terms. There are no comparative uncertainty estimates or event narratives in the information available. The registry also does not report detailed eligibility criteria or participant characteristics, limiting assessment of how broadly the trial population may represent people with Alzheimer’s disease and agitation.
Finally, planning assumptions are identified as illustrations rather than as the trial’s original design justification. The registry record does not report the original sample-size rationale or a complete statistical analysis plan. These gaps are reporting limitations; they do not establish what procedures were or were not conducted outside the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Trial of Dronabinol Adjunctive Treatment of Agitation in Alzheimer's Disease — NCT02792257.
- Registry record last updated 2025-05-09; status last verified 2025-04.
- Results first posted 2025-05-09.
- 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
NCT02792257 is a completed Phase 2 randomized, quadruple-masked, parallel-group pilot trial sponsored by Johns Hopkins University. It compared adjunctive dronabinol with placebo for agitation in Alzheimer’s disease. The registry lists enrollment of 84, with a start date of 2017-03-01 and a primary completion date of 2024-05-31.
Dronabinol was administered twice daily, at 2.5 mg per dose (5mg daily) during Week 1 and 5 mg per dose (10mg daily) for Weeks 2 and 3. Placebo was administered twice daily. The primary outcome was PAS agitation severity over up to 3 weeks; higher scores indicate worse agitation.
The primary-outcome comparison is not reported in the registry record. Safety information includes serious-event counts, other adverse-event counts, and listed serious-event terms, but no comparative statistical analysis is reported.