Impact of Cannabis on Pain and Inflammation Among Patients With Rheumatoid or Psoriatic Arthritis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Impact of Cannabis on Pain and Inflammation Among Patients With Rheumatoid or Psoriatic Arthritis (NCT04269993), a randomized phase 2 study. The primary outcome is Subjective Pain Level Post-vaporization.

2. Clinical Question

The question concerns an acute response under laboratory conditions, not a long-term change in arthritis symptoms. The study description says that pain, affect, and inflammation were of interest, while the posted primary outcome is subjective pain measured with the Short-Form McGill Pain Questionnaire scale. The scale runs from 0, “none,” to 10, “worst possible,” and higher scores indicate more severe pain.

The crossover design means that the planned comparison involved each participant receiving placebo and active THC in separate sessions, with the order randomized. The registry record describes the sessions as separated by at least 2 days. It does not report whether the recorded outcome differed between treatments, how uncertain any estimate was, or how many participants contributed data to an outcome analysis. Therefore, the stated research question can be identified, but its answer cannot be read from the numerical results in the registry record.

3. Trial Design

This Phase 2 study is registered as randomized, double-blind, and crossover. Its brief summary describes a laboratory study of cannabis and pain, affect, and inflammation among patients with rheumatoid or psoriatic arthritis. It describes two cannabis formulations varying in potency and two experimental sessions using a counter-balanced design. The listed intervention is placebo and medium THC/medium CBD; the arm descriptions distinguish placebo cannabis from active THC cannabis.

Participants were assigned to one of two sequences. In one, placebo was given during Session 1 and active THC during Session 2; in the other, active THC was given first and placebo second. The sessions were to be separated by at least 2 days. This sequence structure is central to interpreting a crossover trial: the treatment order varies, and the treatment comparison is intended to be made using observations from both sessions. The registry record does not report further details of the randomization procedure or how the double-blind condition was maintained.

The registry lists enrollment as 3, while the brief summary describes a study with n = 76. These are distinct statements in the record: the listed enrollment is 3, and the summary’s stated study size is n = 76. The status is terminated. The start date is 2022-05-18, and the primary completion date is 2023-07-31. The registry record does not explain the termination or reconcile the listed enrollment with the sample size described in the summary.

No protocol-level details about the intended sample-size justification, planned handling of incomplete sessions, or statistical model are reported in the registry record. In particular, the crossover format alone does not establish which analysis was carried out or whether period, sequence, or carryover effects were considered.

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

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.

6. Primary Endpoint

The registry lists the primary outcome as Subjective Pain Level Post-vaporization, measured over at the termination of the cannabis administration procedure (10 minutes post-completion of cannabis administration).

The primary outcome is titled “Subjective Pain Level Post-vaporization.” It is measured using the Short-Form McGill Pain Questionnaire scale to describe current pain level, with scores from 0, “none,” to 10, “worst possible.” Higher scores indicate more severe pain. The specified assessment is at the termination of the cannabis administration procedure, 10 minutes after completion of cannabis administration.

A continuous pain score can describe the level of pain at a particular assessment time. Comparing such scores after active THC and placebo can address whether the recorded responses differed under those two session conditions. In a crossover study, the same participant may contribute a score under each condition, so the contrast can reflect within-participant change rather than simply comparing unrelated groups. This is a general explanation of the endpoint and design; the registry record does not report the actual scores or the analysis used to compare them.

The endpoint is subjective, meaning it records participants’ reported pain rather than an objective measurement of inflammation. The study description also mentions inflammation and affect, but the posted primary outcome concerns pain. The registry record does not report a threshold for interpreting a change in score as clinically important, nor does it give enough outcome data to assess the size, direction, or precision of any treatment difference.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a continuous pain score represent?

The primary measure is a continuous score on the Short-Form McGill Pain Questionnaire scale, ranging from 0, “none,” to 10, “worst possible.” A mean describes the average score in a group or condition; a standard deviation describes how dispersed individual scores are around that mean. These are different summaries: a mean describes the average level, while a standard deviation describes variation among observations. The registry record identifies the mean and standard deviation as the parameter and dispersion of interest, but it does not report their numerical values.

In general, an estimated treatment contrast expresses the difference in average outcome between conditions, with the order of subtraction defining its sign. For this endpoint, the contrast would need to specify whether active THC is compared with placebo and at which assessment time or times. The registry record does not supply a numerical contrast or a single reduced comparison. No direction or magnitude should therefore be inferred from the outcome title or the trial’s rationale.

Why does the crossover structure matter?

In general, a crossover design records outcomes for the same participant under more than one treatment condition. This pairing can remove some variation between people from the treatment comparison, because each person’s observations are related. The statistical analysis should reflect that dependence; treating the two sets of observations as if they came from entirely separate participants may fail to represent the design accurately.

Period and sequence can also matter in a crossover study. A period effect is a change associated with when a measurement occurs, apart from the treatment condition. A sequence effect concerns the order in which treatments are received. Carryover refers to an influence of an earlier treatment that persists into a later period. These are general crossover concepts, not claims about what happened in this study. The registry record gives the treatment sequences and says sessions were separated by at least 2 days, but it does not report the statistical model or whether period, sequence, or carryover was evaluated.

How should uncertainty be described?

In general, a confidence interval gives a range of values compatible with the data and the method used, while communicating uncertainty around an estimate. A narrow interval indicates greater precision than a wide interval, all else equal. A confidence interval does not guarantee that the true effect lies within the particular interval, and it does not determine whether an effect is important to patients. Interpretation also depends on the scale, the outcome definition, and a threshold for clinical importance. No confidence interval or clinical-importance threshold for this pain outcome is reported in the registry record.

A p-value, in general, measures how unusual data at least as incompatible with a specified null hypothesis would be under the assumptions of the statistical test. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect. The registry record does not report a p-value for the primary outcome. Even if a test result were available, its interpretation would require the estimated contrast and an assessment of uncertainty, not the p-value alone.

What do planning illustrations mean?

Sample-size planning concerns how many participants would be needed under specified assumptions to target a chosen level of statistical power for detecting an effect. The assumptions stated for planning illustrations include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a fraction of the observed effect. These are planning assumptions, not evidence that the trial achieved a particular power. Such illustrations are not observed power and should not be read as the number of participants actually enrolled or analyzed.

The record lists enrollment as 3, and its brief summary describes n = 76. The sample-size assumptions do not resolve that difference or explain the trial’s design rationale. The protocol’s own sample-size justification is not reported in the registry record. Also, because no single primary-outcome comparison is reported, a planning illustration based on an observed effect cannot substitute for an outcome estimate and its uncertainty.

Which analysis details remain unknown?

The registry record does not report the analysis model, the treatment contrast definition, the handling of incomplete or missing observations, or the analysis population. It also does not describe adjustment for baseline values or other covariates. These are important details for understanding how a numerical result would have been obtained, particularly in a small crossover study. They cannot be inferred from the randomization, masking, or crossover labels alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists one outcome measure and one analysis, but the primary outcome is not reduced to one comparison because it is described as having several categories or time points. This leaves uncertainty about which outcome value, time point, or contrast should be treated as the primary numerical result. The record does not report a multiplicity strategy or explain how any choices among outcome categories or time points were handled.

Multiplicity arises when more than one statistical comparison is made. In general, testing many outcomes or time points can increase the chance of obtaining at least one apparently unusual result even when there is no underlying treatment difference. Methods to address that issue depend on the prespecified analysis plan and the family of comparisons being considered. No such plan or adjustment method is reported in the registry record. The fact that the record counts one outcome measure and one analysis does not clarify how its several categories or time points were handled.

Missing-data methods and analysis populations are also not reported in the registry record. The listed enrollment is 3, but the record does not state how many participants completed both sessions, posted an outcome at each session, or were included in an analysis. In a crossover study, incomplete data from one session can affect whether a paired comparison is available. General approaches to missing data make different assumptions about why observations are absent; without a description of missingness and the analysis method, those assumptions cannot be evaluated.

The registry record does not report interim analyses, stopping rules, or protocol-level decisions about analysis populations. These details should not be inferred from the terminated status. The reason for termination and any implications for the outcome analysis are not reported in the registry record.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry record lists 3 participants at risk in each of the Placebo and Active THC groups for serious adverse events, with 0 affected in each. It also lists 3 at risk in each group for other adverse events, with 0 affected in each, and 0 deaths in each group. These are the recorded counts; they do not establish that no adverse events occurred outside the categories or reporting period covered by the registry entry.

In general, an “at risk” count is the denominator against which an affected count is read. Here, the counts are small, so zero recorded events should not be interpreted as proof that an event is impossible or that the treatments have equivalent safety. Sparse event data provide little information about uncommon outcomes. The registry record does not report further event details or a time-at-risk description.

Because this is a crossover study, the group labels describe treatment conditions, but the registry record does not explain whether the same participants contributed to both condition counts. The counts therefore should not be combined or interpreted as independent groups without additional information. No serious adverse event terms are listed. These registry counts describe reported events and do not establish a causal relationship between treatment and any event.

12. What the Result Does, and Does Not, Mean

The registry record establishes that a randomized, double-blind crossover study was registered to assess acute vaporized cannabis administration among patients with rheumatoid or psoriatic arthritis. The primary outcome was subjective pain measured shortly after administration, using a scale from 0 to 10, with higher scores indicating more severe pain. The record lists enrollment as 3 and marks the study as terminated.

It does not establish whether pain scores were higher or lower under active THC than under placebo. No numerical primary-outcome results, treatment contrast, uncertainty interval, or p-value are reported. The record also does not explain the difference between its listed enrollment of 3 and the n = 76 described in its brief summary. Without the outcome data and analysis details, the statistical precision and potential clinical importance of a treatment difference cannot be assessed.

In general, a short-term pain report collected after one laboratory administration addresses a different question from persistent symptoms, repeated use, or longer-term outcomes. This study’s specified time frame is 10 minutes after completion of cannabis administration. Its primary endpoint is a subjective pain score; it does not, by itself, report an objective measure of inflammation. Although the brief summary says that pain, affect, and inflammation were of interest, the primary outcome described in the record is pain.

The posted record therefore documents a study question and design, not an interpretable estimate of treatment effect. The safety counts record no affected participants in the listed serious and other adverse-event categories, but the small recorded at-risk counts and absent event details limit what those counts can establish. Neither the outcome record nor the safety record supports a general conclusion about treatment effectiveness or safety.

13. Why This Trial Matters Statistically

Several statistical features make this record useful to read carefully. First, the crossover structure makes the within-participant comparison important. In general, crossover data should be analyzed in a way that recognizes that two observations from the same person are related. The registry record describes treatment order and session spacing, but it does not report the model used to analyze the paired observations or how period and sequence were addressed.

Second, the relationship between the listed enrollment of 3 and the brief summary’s n = 76 is consequential for interpreting precision. The record does not explain the difference or give the number contributing to the primary outcome. A reader cannot infer the effective sample size from the study design description alone.

Third, a clearly specified comparison is needed to interpret a continuous endpoint. The record identifies a pain scale and assessment timing but does not reduce the primary outcome to one comparison or report numerical results. Without an estimate and uncertainty measure, neither the size nor precision of a difference can be assessed. The record’s sample-size planning assumptions are not a substitute for observed outcome data or a reported protocol justification.

Finally, the safety counts illustrate why denominators matter. Zero affected participants among the recorded at-risk counts is a description of reported events, not proof of equal safety or absence of risk. Taken together, the record distinguishes design information from evidence about outcomes: a randomized design describes how a comparison was intended to be made, while numerical results and transparent analysis details are needed to interpret what the comparison found.

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 limitation for statistical interpretation is the absence of numerical primary-outcome results. The registry record does not report means, standard deviations, a treatment contrast, a confidence interval, or a p-value for subjective pain. It also does not provide a single reduced comparison across the outcome’s several categories or time points. Without those details, the direction, magnitude, and precision of the outcome cannot be assessed.

The record lists enrollment as 3, while its brief summary describes n = 76. It does not explain this difference, report how many participants completed both sessions, or specify the number included in the primary-outcome analysis. The terminated status is recorded, but the reason for termination is not reported in the registry record. The record also does not explain whether termination affected data collection or the planned analysis.

Further limitations arise from missing analysis information. The statistical model, analysis population, treatment contrast definition, handling of missing data, and any approach to period, sequence, or carryover effects are not reported. The record does not state a threshold for clinically important change in the pain score. Nor does it report a sample-size justification from the trial protocol.

The safety information is limited to small recorded at-risk counts and affected counts for serious and other adverse events, plus deaths. It does not give event descriptions or a time-at-risk explanation. These gaps limit interpretation of both the outcome and safety entries; they do not establish why the record is incomplete.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Impact of Cannabis on Pain and Inflammation Among Patients With Rheumatoid or Psoriatic Arthritis — NCT04269993.
• Registry record last updated 2025-04-01; status last verified 2025-03.
• Results first posted 2025-03-13.
• 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.

18. Record Summary

This Phase 2 trial is listed as randomized, double-blind, and crossover, with a terminated status. It studied acute vaporized cannabis administration among patients with rheumatoid or psoriatic arthritis. The two sequences were placebo followed by active THC, or active THC followed by placebo, with sessions separated by at least 2 days. The primary outcome was subjective pain on the Short-Form McGill Pain Questionnaire scale, assessed 10 minutes after cannabis administration was completed.

The registry lists enrollment as 3, while the brief summary describes n = 76; the record does not explain the difference. It does not report numerical primary-outcome results, a single treatment comparison, or the analysis details needed to assess precision. Serious and other adverse-event counts are listed as 0 affected among 3 at risk in each condition, with 0 deaths. The reason for termination and the protocol’s sample-size justification are not reported in the registry record.