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 Laboratory Study of Cannabidiol on the Effects of Smoked Marijuana (NCT01844687), a randomized phase 2 study. The primary outcome is Mood Scale - Subscale 'Feeling High'.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01844687 |
| Phase | Phase 2 |
| Condition | Smoking, Marijuana |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Triple |
| Enrollment | 50 |
| Arms in the primary outcome | n/a |
| Lead sponsor | National Institute on Drug Abuse (NIDA) |
| Results posted | Yes |
2. Clinical Question
Population
The primary-outcome population is described as all 31 completers. The registry lists enrollment of 50. It does not provide additional characteristics of the participants in the record, so the population cannot be characterized further from these details.
Intervention
The study examined oral cannabidiol (CBD) at 0, 200, 400, and 800 mg in combination with smoked marijuana. The arm descriptions include active marijuana and inactive marijuana at each CBD dose. Active marijuana cigarettes are described as containing 5.30% THC, while inactive marijuana cigarettes are described as containing 0.01% THC.
Comparator
The study’s conditions allow examination of different CBD doses with active or inactive marijuana. The registry does not identify a single comparator for the primary endpoint, and the outcome has several categories or time points rather than one reduced comparison. No single pairwise contrast should therefore be assumed to represent the full study question.
Primary question
The primary measure concerns participants’ self-rated feeling of being high after smoking a marijuana cigarette. The study objective was to assess whether oral CBD, at the listed doses, had effects on the subjective effects of smoked marijuana, including in the inactive-marijuana conditions. The record does not report the numerical primary-outcome results needed to describe the size or precision of any observed effect.
3. Trial Design
This is a Phase 2, randomized, triple-masked crossover study sponsored by the National Institute on Drug Abuse (NIDA). The registry lists enrollment of 50 and a status of completed. The listed study dates are 2013-05 for start and 2014-10 for primary completion. The primary-outcome population is described as all 31 completers.
The study concerns oral CBD given with smoked marijuana. The arm descriptions cover active marijuana with 0, 200, 400, or 800 mg CBD, and inactive marijuana with those same CBD doses. The active-marijuana cigarettes are described in the arm entries as containing 5.30% THC; the inactive-marijuana cigarettes are described as containing 0.01% THC. The brief objective refers to active marijuana as 5.6% THC, which differs from the 5.30% stated in the arm descriptions. The record does not explain this difference.
A crossover design means, as a general statistical concept, that participants can receive more than one study condition at different times. This can allow comparisons within the same participant, but it also means measurements may be related rather than independent. The registry record does not report the condition sequence, the interval between conditions, or the procedures used to address possible carryover. Randomization and triple masking are recorded, but the details of their implementation are not reported.
The objective names subjective, reinforcing, cognitive, and cardiovascular effects. The primary outcome listed is a mood-scale subscale, “Feeling High.” No statistical analysis is listed in the registry record, and the record does not report a protocol-level statistical plan.
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.
Visit 1
| Stage | Single Group |
|---|---|
| STARTED | 50 |
| COMPLETED | 42 |
| NOT COMPLETED | 8 |
Reasons for not completing this period:
| Reason | Single Group |
|---|---|
| Protocol Violation | 3 |
| Lost to Follow-up | 5 |
Visit 2
| Stage | Single Group |
|---|---|
| STARTED | 42 |
| COMPLETED | 40 |
| NOT COMPLETED | 2 |
Reasons for not completing this period:
| Reason | Single Group |
|---|---|
| Withdrawal by Subject | 1 |
| Protocol Violation | 1 |
Visit 3
| Stage | Single Group |
|---|---|
| STARTED | 40 |
| COMPLETED | 35 |
| NOT COMPLETED | 5 |
Reasons for not completing this period:
| Reason | Single Group |
|---|---|
| Lost to Follow-up | 1 |
| Withdrawal by Subject | 3 |
| child care problems | 1 |
Visit 4
| Stage | Single Group |
|---|---|
| STARTED | 35 |
| COMPLETED | 31 |
| NOT COMPLETED | 4 |
Reasons for not completing this period:
| Reason | Single Group |
|---|---|
| Pregnancy | 1 |
| Lost to Follow-up | 1 |
| Withdrawal by Subject | 2 |
Analysis population for the primary outcome, as defined in the registry: all 31 completers
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.
Population: count - only those participants who completed all 8 visits (31)
| Characteristic | Unit | Single Group |
|---|---|---|
| Participants analysed | 31 | |
| Age, Continuous | years | 29.1 (SD 9.1) |
| Sex: Female, Male: Female | Participants | 14 |
| Sex: Female, Male: Male | Participants | 17 |
| Race/Ethnicity, Customized: Black | participants | 15 |
| Race/Ethnicity, Customized: White | participants | 12 |
| Race/Ethnicity, Customized: mixed | participants | 4 |
| Region of Enrollment: United States | participants | 31 |
| cannabis use (number of days per week) | days per week | 6.5 (SD 1.0) |
| cannabis cigarettes per day | cannabis cigarettes used per day | 5.1 (SD 5.3) |
| tobacco cigarette smokers | participants | 18 |
| alcohol drinkers | participants | 14 |
6. Primary Endpoint
The registry lists the primary outcome as Mood Scale - Subscale 'Feeling High', measured over two hours before and after marijuana cigarette smoking.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Error |
| Unit | units on a scale VAS 1-100 mm |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the “Feeling High” subscale of a mood scale. Participants rated how much they felt a “high” feeling from smoked marijuana using a visual analog scale from 1 to 100 mm, with 1 meaning “Not at all” and 100 meaning “extremely.” The registry identifies the measure as a mean of a continuous outcome and describes its dispersion as a standard error. The assessment timeframe is two hours before and after marijuana cigarette smoking.
As a general measurement principle, a self-rating scale can capture a participant’s subjective experience directly. A continuous score also permits description of the average level and variation in ratings, rather than reducing responses to a yes-or-no category. These are reasons such measures can be useful for studying subjective effects; they do not establish that the measure captures every relevant aspect of an experience.
The registry does not report the numerical mean or standard error for this primary endpoint, nor does it report a confidence interval or test result. It also does not identify one single time point or contrast as the result to interpret. The record notes that the primary outcome has several categories or time points and was not reduced to one comparison. Consequently, the measure is described, but its observed pattern and precision cannot be evaluated from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a primary measure and a population of all 31 completers, but it does not give the numerical “Feeling High” results. It lists no analyses. No mean, standard error, confidence interval, or p-value for the primary outcome is reported in the registry record. There is therefore no posted numerical estimate from which to describe the magnitude, direction, or precision of the primary-outcome findings.
The study objective covers CBD doses of 0, 200, 400, and 800 mg alongside active and inactive smoked marijuana. Because the outcome includes several categories or time points, interpreting it requires clarity about which condition contrasts and measurement times are being compared. The registry record does not reduce this outcome to a single comparison. Without a stated contrast and its estimate, it is not possible to determine from the registry whether ratings differed across conditions, or how large any such differences were.
For a continuous outcome, a mean describes the average score in the relevant group or condition. A standard error describes the uncertainty in an estimated mean; it is not the same as the spread of individual participant ratings. A confidence interval, if reported, would show a range of values compatible with the data under the model and assumptions used. These are general statistical interpretations, not results reported for this study.
The crossover design can support within-participant comparisons as a general design feature, because the same person may contribute observations under multiple conditions. Those observations are usually statistically related. The analysis needs to account for that dependence and for the structure of repeated measurements. The registry does not report an analysis method, the treatment sequence, or how time points were handled. It is not possible to assess whether or how those features were incorporated into the sponsor’s analysis.
The reported enrollment and completer counts do not, by themselves, establish how many observations contributed to each primary-outcome estimate. The record describes all 31 completers as the primary population, but does not report missing primary-outcome measurements, exclusions, or an analysis population beyond that description. Nor does it provide outcome-specific denominators.
Accordingly, the posted record supports a description of the study question, design, and endpoint, but not a conclusion about the numerical primary-outcome findings. An absence of reported estimates is not evidence that conditions were equivalent or that an effect was absent. It means the registry record does not give the results needed to evaluate the size and precision of the endpoint differences.
9. Statistical Methods Explained
The study is described as randomized, triple-masked, and crossover. These design terms describe different features. Randomization concerns how study conditions are assigned. Masking concerns keeping treatment information unknown to specified people involved in the study or its assessment. Crossover means participants can receive multiple conditions over time. The registry names these features but does not provide operational details, such as the assignment sequence or exactly who was masked.
What does the crossover design imply?
In general, crossover studies can compare outcomes from different conditions within the same participant. Each participant can therefore serve as a reference for their own measurements, which can reduce the influence of stable differences between participants. The tradeoff is that measurements from one participant are related. Appropriate analysis generally accounts for within-participant dependence, condition order, and possible carryover from an earlier condition. These are general statistical considerations; the registry does not report how the study handled them, whether there was a washout interval, or what model was used.
What does the primary measure represent?
The primary endpoint is a continuous rating of feeling high on a visual analog scale from 1 to 100 mm. The registry specifies a mean as the outcome parameter and a standard error as the dispersion measure. In general, the mean describes the average observed rating for a defined condition and time point. The standard error describes uncertainty in that estimated mean. It does not describe how widely individual scores vary; a standard deviation is commonly used for that different purpose. No numerical primary-outcome means or standard errors are reported in the registry record.
A confidence interval is a general way to express uncertainty around an estimate. Its width depends on factors such as the amount and variability of information and the analysis method. The record does not report a confidence interval for the primary endpoint. No result should be inferred from the endpoint’s scale or from the study’s design alone.
How should multiple conditions and times be interpreted?
The study includes four CBD dose levels in both active- and inactive-marijuana conditions, and the primary measure is described over a timeframe of two hours before and after smoking. This creates multiple possible condition and time comparisons. In general, evaluating many comparisons can raise the chance of finding an apparently notable result by chance if each is tested separately. A prespecified primary contrast, an overall test, or an adjustment for multiple comparisons can help define how such results are interpreted. The registry does not report which approach, if any, was used. It notes that the primary outcome has several categories or time points and was not reduced to one comparison.
The registry lists no analyses, so it does not provide an inferential method, test statistic, confidence interval, or p-value. It also does not report a statistical plan. The significance threshold and the handling of repeated observations or multiple comparisons are therefore not reported in the registry record.
What does the sample-size information mean?
The registry’s sample-size assumptions describe a planning illustration based on an observed effect, rather than the study’s own design. The stated assumptions are 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 stated fraction of the observed effect. For outcomes other than time-to-event outcomes, such illustrations refer to participants per arm; time-to-event illustrations refer to the total number of events. These are general planning assumptions, not evidence of the trial’s planned sample-size justification or its achieved power.
The record does not report the trial’s own sample-size justification or any numerical sample-size illustration results. It would also be incorrect to interpret an illustration based on an observed effect as observed power. Such an illustration concerns hypothetical planning under specified assumptions, while observed outcome estimates and their uncertainty are separate matters. Since the primary numerical results are not reported, the magnitude used for any such illustration is not available in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The primary outcome is described across several categories or time points, and the registry indicates it was not reduced to one comparison. The study also includes multiple CBD doses and active- and inactive-marijuana conditions. These features create more than one possible way to compare ratings. The registry record does not identify a single primary contrast, explain whether an overall test was used, or report an adjustment for multiple comparisons. The statistical plan is not reported in the registry record.
As a general statistical issue, testing multiple contrasts can increase the chance of at least one apparently unusual result when each test is considered separately. Interpretation therefore depends on how comparisons were chosen and whether the analysis accounted for multiplicity. The registry does not provide enough information to determine how this issue was handled, and it reports no analysis results with which to assess the consequences.
The record describes the primary population as all 31 completers and lists enrollment of 50. It does not report how incomplete participation was handled, whether primary endpoint observations were missing, or whether any imputation method was used. It also does not report an intention-to-treat analysis or another analysis population. The distinction between enrollment and completers alone does not establish the reasons for non-completion or the effect of missing data on the results.
For a crossover study, missing observations can affect within-participant comparisons, particularly if the available conditions differ across participants. As a general matter, the analysis method and assumptions about missingness influence interpretation. Neither the missing-data approach nor outcome-specific denominators are reported in the registry record. These gaps limit assessment of multiplicity, completeness, and the population represented by any primary-outcome estimate.
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 |
|---|---|---|---|
| Active MJ With 0 mg CBD | 0 | 50 | 0.0% |
| Active MJ With 200 mg CBD | 0 | 50 | 0.0% |
| Active MJ With 400 mg CBD | 0 | 50 | 0.0% |
| Active MJ With 800 mg CBD | 0 | 50 | 0.0% |
| Inactive MJ With 0 mg CBD | 0 | 50 | 0.0% |
| Inactive MJ With 200 mg CBD | 0 | 50 | 0.0% |
| Inactive MJ With 400 mg CBD | 0 | 50 | 0.0% |
| Inactive MJ With 800 mg CBD | 0 | 50 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Active MJ With 0 mg CBD | 0 of 50 |
| Active MJ With 200 mg CBD | 0 of 50 |
| Active MJ With 400 mg CBD | 0 of 50 |
| Active MJ With 800 mg CBD | 0 of 50 |
| Inactive MJ With 0 mg CBD | 0 of 50 |
| Inactive MJ With 200 mg CBD | 0 of 50 |
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 |
|---|---|
| Active MJ With 0 mg CBD | 5 of 50 |
| Active MJ With 200 mg CBD | 8 of 50 |
| Active MJ With 400 mg CBD | 4 of 50 |
| Active MJ With 800 mg CBD | 3 of 50 |
| Inactive MJ With 0 mg CBD | 2 of 50 |
| Inactive MJ With 200 mg CBD | 1 of 50 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Active MJ With 0 mg CBD | Active MJ With 200 mg CBD | Active MJ With 400 mg CBD | Active MJ With 800 mg CBD | Inactive MJ With 0 mg CBD | Inactive MJ With 200 mg CBD |
|---|---|---|---|---|---|---|---|
| headache | Nervous system disorders | 1 of 50 | 1 of 50 | 1 of 50 | 1 of 50 | 1 of 50 | 1 of 50 |
| Gastrointestinal Upset | Gastrointestinal disorders | 1 of 50 | 2 of 50 | 0 of 50 | 2 of 50 | 0 of 50 | 0 of 50 |
| anxiety | Psychiatric disorders | 1 of 50 | 3 of 50 | 0 of 50 | 0 of 50 | 0 of 50 | 0 of 50 |
| Blurred Vision | Eye disorders | 1 of 50 | 0 of 50 | 1 of 50 | 0 of 50 | 1 of 50 | 0 of 50 |
| fatigue | General disorders | 0 of 50 | 1 of 50 | 0 of 50 | 1 of 50 | 0 of 50 | 0 of 50 |
| Cold Symptoms | Infections and infestations | 1 of 50 | 0 of 50 | 1 of 50 | 0 of 50 | 0 of 50 | 0 of 50 |
| Pain (foot/hand/tooth) | Musculoskeletal and connective tissue disorders | 0 of 50 | 2 of 50 | 0 of 50 | 0 of 50 | 0 of 50 | 0 of 50 |
| Increased heart rate | Cardiac disorders | 0 of 50 | 0 of 50 | 1 of 50 | 0 of 50 | 0 of 50 | 0 of 50 |
The registry lists serious adverse events for each of the eight marijuana-and-CBD conditions. In every listed condition, 50 are recorded as at risk, zero as affected by a serious adverse event, and zero deaths. These are group-level entries in the record; they should be read as reported, not combined into a total number of unique participants across conditions. The crossover design means the same participant may be represented under more than one condition, but the registry does not describe the safety counting procedures in detail.
The registry also lists non-serious adverse events by condition. For active marijuana with 0, 200, 400, and 800 mg CBD, the recorded counts are 5, 8, 4, and 3, respectively. For inactive marijuana with 0, 200, 400, and 800 mg CBD, the counts are 2, 1, 3, and 6, respectively. The record lists 50 at risk in each condition. These are counts as recorded, not calculated rates, and the entries do not establish that an event was caused by a particular condition.
The registry gives no serious adverse-event terms in its listed top terms. The absence of reported serious events in these entries does not establish that no adverse experiences of any kind occurred: non-serious events are listed, and the safety record is limited to what is recorded in the registry. The entries also do not provide details about event duration, severity beyond the serious/non-serious distinction, or clinical assessment.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a randomized, triple-masked crossover study examined oral CBD with active or inactive smoked marijuana. It identifies “Feeling High” as the primary measure and describes how participants rated that experience. It also records the study’s enrollment and completer population, along with adverse-event counts by condition.
What the record does not establish is the primary outcome result. Numerical means, standard errors, confidence intervals, and test results are not reported, and the registry lists no analyses. Thus, the posted record does not support a quantitative account of whether ratings varied by CBD dose, marijuana condition, or time point, nor of the precision of any such difference. Missing numerical results should not be interpreted as evidence of no difference.
The study objective names subjective, reinforcing, cognitive, and cardiovascular effects, but the primary measure described in detail is subjective. The listed primary endpoint alone cannot answer every question about the broader objective. The registry record does not report the corresponding numerical findings for the other domains in the information.
The safety entries report zero serious adverse events and zero deaths in each listed condition, alongside counts of non-serious adverse events. These entries describe what the registry records; they do not establish causation or provide a complete characterization of safety. They should also be read in light of the crossover design and the record’s lack of detail about safety counting.
In general, a study’s design can clarify which comparisons it was intended to make, while estimates and uncertainty are needed to evaluate the observed data. Here, the design and outcome description are available, but the numerical primary results and analysis approach are not. Any interpretation should keep that distinction clear and avoid treating the study objective as a finding.
13. Why This Trial Matters Statistically
Statistically, this study raises several issues that are important when reading clinical research. Its crossover design can make within-participant comparisons informative, but repeated observations are related and analysis should reflect that structure. The registry identifies the design but does not report the analysis model, condition sequence, or procedures for addressing possible carryover. Those details matter for understanding how a contrast would be estimated.
The study also includes multiple CBD doses, active and inactive marijuana conditions, and a primary measure described across multiple time points. That makes the definition of the target comparison important. The registry explicitly notes that the primary outcome has several categories or time points and was not reduced to one comparison. Without a clearly stated contrast or analysis plan, the registry record does not establish how the primary question was operationalized for statistical testing.
The endpoint is a subjective continuous rating. Its mean and standard error would convey different information: the mean would describe the average rating, while the standard error would describe precision in the estimated mean. Neither numerical measure is reported for the primary endpoint, and no confidence interval or analysis result is listed. This illustrates why a design description alone cannot substitute for results and uncertainty estimates.
The record also distinguishes enrollment of 50 from a primary population of all 31 completers. Since missing-data handling and outcome-specific denominators are not reported, readers cannot determine from the record how incomplete participation affected the analyzed data. These design and reporting questions are relevant to interpreting the evidence, independent of any conclusion about the study’s clinical implications.
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 of the registry information is that it does not report numerical results for the primary endpoint. Although the endpoint, scale, timeframe, and primary population are described, the mean and standard error are absent. The registry also lists no analyses, so there are no reported confidence intervals, p-values, or model estimates from which to evaluate the primary outcome’s magnitude and precision.
The primary outcome includes several categories or time points and is not reduced to one comparison. The registry does not identify a specific primary contrast or explain how multiple comparisons were handled. The analysis plan, including the method for accounting for repeated observations in the crossover design, is not reported. The condition sequence and any procedures addressing possible carryover are also not reported in the registry record.
The registry describes the primary population as all 31 completers and lists enrollment of 50, but does not explain the difference or report reasons for non-completion. Missing primary outcome data, exclusions, imputation, and the analysis population are not reported. These omissions prevent assessment of how missingness may have affected the results.
There is also a difference between the active-marijuana THC concentration stated in the brief objective, 5.6%, and the arm descriptions, 5.30%. The record does not explain the discrepancy. The safety entries provide counts by condition but do not give detailed event descriptions in the information. Together, these limitations mean the record is more informative about the planned question and broad design than about the study’s statistical findings.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Laboratory Study of Cannabidiol on the Effects of Smoked Marijuana — NCT01844687.
- Registry record last updated 2019-12-09; status last verified 2017-04.
- Results first posted 2017-04-25.
- 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
NCT01844687 is a completed Phase 2 randomized, triple-masked crossover study sponsored by the National Institute on Drug Abuse (NIDA). The record lists enrollment of 50 and a primary-outcome population of all 31 completers. It concerns oral CBD at 0, 200, 400, and 800 mg with active or inactive smoked marijuana.
The primary endpoint is a mean rating of “Feeling High” on a visual analog scale from 1 to 100 mm, assessed two hours before and after smoking. The registry lists no analyses and does not report numerical primary-outcome results or a statistical plan. It records zero serious adverse events and zero deaths in each condition, as well as non-serious adverse-event counts. The record therefore describes the study design and endpoint but does not permit quantitative interpretation of the primary findings.