Social Media Intervention for Cannabis Use in Emerging Adults: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Social Media Intervention for Cannabis Use in Emerging Adults (NCT04187989), a randomized na study. The primary outcome is Frequency of Cannabis Use as Reported on the Timeline Follow-Back (TLFB).

2. Clinical Question

The primary outcome is a continuous measure: days of cannabis use during a thirty-day reporting period. The registry reports a mean of 18.0 days for the intervention group and 14.9 days for control. The recalculated unadjusted mean difference is 3.1 days, with the intervention group higher. Its confidence interval includes values on both sides of zero, and the unadjusted p-value is 0.121. These results describe the posted data; they do not establish why the groups differed or whether any difference was caused by the intervention.

The clinical question is about a specific intervention, comparator, self-reported outcome, and follow-up time. It is not a general test of social media use, all cannabis-related outcomes, or longer-term effects. The registry record does not report enough detail to characterize the participants beyond the study’s focus on emerging adults and Facebook users.

3. Trial Design

The registry describes a randomized, parallel-group study with no masking. Participants were assigned to a social media intervention or an Attention-Control E-News control condition. The intervention was a Facebook page intended to deliver health information about well-being and reducing risky behaviors. The registry does not describe the control content in comparable detail.

The recorded enrollment is 149. For the primary outcome at three months after baseline, the reported group summaries include 70 participants in the intervention group and 65 in control. These are the outcome-summary group sizes; the registry record does not explain the relationship between enrollment and the number contributing to this outcome. The recorded status is completed. The study start date is 2020-02-03, and the primary completion date is 2020-12-18.

The primary endpoint was the mean number of days of cannabis use, measured by a thirty-day Timeline Follow-Back self-report, at three months post baseline. Additional registry outcomes concern perceived risk of cannabis use, peer approval or disapproval, cannabis-impaired driving, and other drug use. The record includes secondary results at specified follow-up times, but it does not contain numeric results for every outcome named in the registry.

The record does not report the original sample-size justification, planned analysis populations, handling of missing observations, or a detailed statistical analysis plan. It also does not report whether an interim analysis was planned or conducted. Randomization supports a group comparison by design, but the available registry information alone cannot establish how assignment was generated, concealed, or implemented.

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 - 3-Month Follow-Up

Reasons for not completing this period:

Overall Study - 6-Month Follow-Up

Reasons for not completing this period:

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 Frequency of Cannabis Use as Reported on the Timeline Follow-Back (TLFB), measured over 3-months post baseline.

The primary endpoint is the mean number of days on which participants reported cannabis use in the thirty days before assessment, measured using the Timeline Follow-Back. The outcome is assessed three months after baseline. The registry describes it as a self-report and specifies days as its unit.

A count of use-days gives a direct description of frequency during the reporting window. Comparing group means addresses whether average reported frequency differed between those assigned to the Facebook intervention and those assigned to Attention-Control E-News. The measure does not, by itself, describe amount used on a use-day, impairment, dependence, or the reasons for use. Nor does one thirty-day reporting window establish a participant’s pattern across other periods.

The posted summaries are 18.0 days in the intervention group and 14.9 days in control. The recalculated unadjusted mean difference is 3.1 days, intervention minus control. A mean summarizes the group outcome but does not show the distribution of individual responses. The registry reports standard deviations of 11.5 and 11.7 days, respectively, indicating considerable variation around each group mean. The endpoint is therefore useful for comparing average frequency, while leaving individual patterns and other dimensions of cannabis use unanswered.

The registry record does not report the rationale for choosing this endpoint or whether the analysis adjusted for baseline use or other characteristics.

7. Results Posted in the Registry

• Social Media Intervention: mean 18.00 versus 14.90 on control; difference 3.10 (95% CI -0.82 to 7.02), standardized effect d = 0.27; z-test p = 0.121.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Perceived Risk of Cannabis Use as Measured by 2 Modified Items From the Monitoring the Future Survey

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Social Media Intervention: mean 3.10 versus 3.50 on control; difference -0.40 (95% CI -0.77 to -0.03), standardized effect d = -0.36; z-test p = 0.035.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Social Media Intervention than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Perceived Risk of Cannabis Use as Measured by Modified Items From the Monitoring the Future Survey

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Social Media Intervention: mean 3.30 versus 3.50 on control; difference -0.20 (95% CI -0.63 to 0.23), standardized effect d = -0.16; z-test p = 0.357.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Social Media Intervention and the control. The interval gives the range of effects that remain compatible with the data.

Peer Approval/Disapproval of Cannabis Use as Measured by Item Modified From Monitoring the Future Survey

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Social Media Intervention: mean 1.00 versus 1.00 on control; difference 0.00 (95% CI -0.05 to 0.05), standardized effect d = 0.00; z-test p = 1.000.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Social Media Intervention and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes address related but distinct aspects of cannabis-related beliefs and behavior. The results included in the registry record cover perceived risk at three months and six months after baseline and peer approval or disapproval at three months. Other named outcomes concern impaired driving and other drug use, but their numeric results are not reported in the registry record. The registry lists 12 secondary outcomes as posted, while only a subset of numerical secondary comparisons is available in the results represented in the record.

Overall, these secondary measures do not form a consistent, comprehensive account of the primary outcome. They assess perceptions and social context as well as behavior, and they are measured at different follow-up times. A difference in perceived risk would not by itself establish a difference in use-days; likewise, a result at one follow-up does not establish a persistent pattern at another. The primary endpoint remains the direct comparison of self-reported cannabis-use frequency at three months.

Secondary comparisons deserve more cautious interpretation when many outcomes are assessed. Even if each individual test uses a conventional significance threshold, examining many outcomes can increase the chance of at least one nominally unusual result under a setting with no true effects. The registry record does not report a multiplicity adjustment, a hierarchy of secondary hypotheses, or a plan identifying which secondary outcomes were confirmatory. Consequently, unadjusted secondary p-values are best treated as exploratory signals rather than as stand-alone confirmation. This caution applies regardless of whether a particular nominal result is below a conventional threshold.

Because detailed methods and numeric results are unavailable for some named outcomes, the full pattern across all registered secondary measures cannot be assessed from the registry record. The secondary results should not be combined informally into a single overall conclusion about intervention impact.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Perceived Risk of Cannabis Use as Measured by 2 Modified Items From the Monitoring the Future Survey
• Perceived Risk of Cannabis Use as Measured by Modified Items From the Monitoring the Future Survey
• Peer Approval/Disapproval of Cannabis Use as Measured by Item Modified From Monitoring the Future Survey
• Peer Approval/Disapproval of Cannabis Use as Measured by Item Modified From Monitoring the Future Survey
• Cannabis Impaired Driving as Measured by 5 Items From the Modified Young Adult Driving Questionnaire
• Cannabis Impaired Driving as Measured by 5 Items From the Modified Young Adult Driving Questionnaire
• Other Drug Use as Measured by Items Modified From Monitoring the Future Survey
• Other Drug Use as Measured by Items Modified From Monitoring the Future Survey

9. Statistical Interpretation

10. Statistical Methods Explained

What does the mean difference represent?

The primary outcome is continuous, and the posted group summaries report means and standard deviations. A mean difference expresses the intervention-group mean relative to the control-group mean in the endpoint’s original unit, days. The recalculated unadjusted difference is 3.1 days, with the direction defined as intervention minus control. Positive values therefore correspond to a higher mean in the intervention group. This is a descriptive comparison of the posted summaries, not an adjusted estimate from an individual-level model.

Standard deviation describes how spread out observations are around a group mean. It is not the same as the standard error, which describes the precision of an estimated mean. The registry’s reported standard deviations are 11.5 days for the intervention group and 11.7 days for control. The wide individual variation relative to the means is relevant when interpreting how much information the group summaries provide about a difference.

What does the confidence interval add?

A confidence interval gives a range of estimates compatible with the data and the method used to construct it. In repeated use of the same procedure under its assumptions, the stated confidence level describes how often such intervals would contain the underlying parameter. It is not a probability statement that the particular true value lies in this particular interval.

For the recalculated primary mean difference, the interval includes zero and extends in both directions. This means the posted summary statistics are compatible with no mean difference, as well as with differences favoring either direction. Its width is important: the estimate does not tightly locate the size of a possible difference. The interval is for the simple unadjusted comparison, not necessarily the sponsor’s analysis.

How should the p-value be read?

The unadjusted p-value of 0.121 is a measure, under the test’s assumptions and a null hypothesis of no group difference, of how unusual data at least as incompatible with that null would be. It is not the probability that the null hypothesis is true, nor a measure of clinical importance. It does not answer whether the study had adequate precision for every effect of interest. The registry does not report whether the sponsor’s analysis used the same data, estimand, or assumptions as the recalculation.

Why does variation matter?

When outcomes vary substantially among participants, the group averages can be estimated less precisely unless the study includes enough information to offset that variation. This is one reason to interpret a mean difference alongside its uncertainty interval rather than relying on the direction of the means alone. For outcomes such as use-days, distributions may also have features that a mean and standard deviation do not display, including uneven concentrations or unusually high values. The registry record does not report distributional diagnostics or analyses addressing such features, so it is not possible to assess them from the posted summaries.

What is the role of Cohen’s D?

Cohen’s D expresses a mean difference in standard-deviation units, making it a standardized effect size rather than a difference measured in days. The sponsor reports Cohen’s D for the primary comparison as -.006, with a 95% confidence interval from -.478 to .466 and p = .980. The recalculated comparison instead reports a mean difference in days and an unadjusted p-value of 0.121. Standardized and unstandardized effects answer related but distinct questions. The registry record does not supply enough analysis detail to explain why the sponsor’s reported result differs from the simple calculation based on the posted group summaries.

Secondary outcomes are also continuous in the results included in the record. Their point estimates, uncertainty, and nominal p-values can be interpreted using the same general ideas, but they address different constructs and time points. A result on perceived risk is not interchangeable with a result on frequency of cannabis use. Results across several endpoints also raise the possibility of chance findings when many comparisons are examined; whether and how the study controlled this is not reported in the registry record.

General statistical interpretation depends on the design and assumptions behind an analysis. Random assignment is relevant to comparing assigned groups, but does not remove the need to understand missing observations, adherence, outcome measurement, and the analysis population. Details about these matters, including any adjustment for baseline measurements, are not reported in the registry record. Consequently, the recalculation should be understood as a simple unadjusted comparison of posted summary statistics, not as a replacement for a fully specified trial analysis.

11. Confidence Intervals and Precision

The primary recalculated mean difference is 3.1 cannabis-use days, intervention minus control. Its confidence interval crosses zero, spanning estimates in both directions. This indicates that the posted summaries do not determine the direction of the underlying group difference with precision. The interval also allows a range of possible magnitudes, so the point estimate should not be interpreted as an exact or stable measure of the intervention’s effect.

Precision is distinct from whether a result is statistically significant. The unadjusted p-value is 0.121, but the interval is more informative about which values remain compatible with the simple comparison. It does not show that the true effect is zero, and it does not establish that the effect is large. A confidence interval describes uncertainty under the method’s assumptions; it does not incorporate every possible source of bias or uncertainty in how participants were selected, measured, or analyzed.

The posted standard deviations, 11.5 days in the intervention group and 11.7 days in control, show substantial spread in individual use-days around the means. Group averages can obscure that variation. The confidence interval is based on the unadjusted summary-statistic comparison and should not be assumed to match the sponsor’s reported confidence interval for Cohen’s D. The sponsor’s 95% interval, from -.478 to .466, concerns a standardized effect and is a separate reported analysis.

More precise conclusions would require clear information about the analysis population, missing outcome data, and the sponsor’s analysis method. Those details are not reported in the registry record. The posted estimate is therefore best read as a broad, uncertain comparison rather than a definitive measurement of a small or absent difference.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning illustrations translate an observed effect into hypothetical sample-size requirements under stated assumptions. For these continuous outcomes, the figures are participants per arm, not total events. The assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Each planning scenario uses the stated fraction of the observed effect as the effect to detect. The original trial’s own sample-size assumptions and justification are not reported in the registry record.

The 80% power column describes the number of participants per arm that the illustration estimates would be needed for an 80% chance of detecting the chosen effect under those assumptions, if that effect were the true one. The 90% power column describes the corresponding requirement for a 90% chance. Higher planned power generally requires more participants for the same target effect.

The rows consider planning for 100%, 75%, or 50% of the observed effect. Planning for a smaller effect requires more participants per arm, because a smaller difference is harder to distinguish from random variation. For example, the primary-outcome illustration lists 220 participants per arm for 80% power when planning for the full observed effect, and 879 participants per arm when planning for 50% of it. These figures are hypothetical planning illustrations based on the observed estimate, not the trial’s original design calculation. This is not observed power. The calculations do not establish what the trial was designed to detect or explain its results.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 3.100; pooled standard deviation σ = 11.597.
2. n = 2 × (1.96 + 0.842)² × 11.597² / 3.100² = 219.7, rounded up to 220 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 3.1                      # observed difference in means
sigma <- 11.5966711583492                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(4187989)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 220 (80% power), 295 (90% power)
 75% of observed effect: n per arm = 391 (80% power), 523 (90% power)
 50% of observed effect: n per arm = 879 (80% power), 1,177 (90% power)
power.t.test: 220.6 
Simulated power at n = 220 per arm: 0.795 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The registry reports a sponsor analysis of the primary comparison using a two-sided t-test and Cohen’s D. The reported standardized estimate is -.006, its 95% confidence interval runs from -.478 to .466, and the reported p-value is .980. This result is distinct from the unadjusted recalculation using the posted group means and standard deviations, which estimates a mean difference of 3.1 days and gives an unadjusted p-value of 0.121.

The two results use different effect measures: Cohen’s D is expressed in standard-deviation units, while the recalculated estimate is in days. However, the reported sponsor estimate and the posted means do not appear to align in direction or magnitude. The registry record does not explain the analysis details that would allow the results to be reconciled. It does not state whether the sponsor analysis used a different analysis population, a model, baseline adjustment, or other data-handling choices.

The sponsor result should therefore be read as the analysis reported in the registry, while the recalculation is a separate, simple comparison of the posted summaries. Neither should be silently substituted for the other. The available record does not establish which analysis choices account for their different numerical results.

15. Multiplicity, Missing Data and Analysis Populations

The registry describes multiple outcome measures and analyses, including primary and secondary outcomes. Testing many outcomes can increase the chance that at least one result appears unusual by chance. Statistical approaches such as adjustment, prespecified outcome hierarchies, or clearly labeled exploratory analyses can help readers understand this issue. Whether the trial used any such approach, and how it treated repeated assessments or multiple comparisons, is not reported in the registry record. The unadjusted secondary results should therefore be interpreted cautiously.

Missing-data handling is also important because the primary endpoint summaries include 70 participants in the intervention group and 65 in control, while recorded enrollment is 149. The registry record does not explain why these counts differ, whether outcome data were unavailable, or how any missing observations were handled. It does not report an imputation approach, a complete-case rule, or sensitivity analyses for missing outcomes. The difference in recorded counts alone does not identify the reason for missingness or establish that the analysis is biased.

The analysis population is not described in enough detail to determine whether participants were analyzed according to original assignment, whether any participants were excluded, or whether the reported summaries include all randomized participants with available data. Although the design is randomized, interpretation depends on how assignment and outcomes were handled after randomization. The registry record also does not report adherence to the intervention or engagement with the Facebook page.

These omissions do not prove that the study failed to use appropriate methods. They limit what can be concluded from the registry record. In particular, readers cannot assess how missingness, multiplicity, baseline measurements, or analysis-population choices may affect the reported estimates.

16. 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 reports zero serious adverse events in the intervention group among 76 participants at risk and zero in the control group among 73 participants at risk. It also reports zero other adverse events in each group among the same respective numbers at risk, and zero deaths in both groups. No top serious-event terms are listed.

These figures describe the adverse-event information recorded during the study; they do not establish that no adverse events occurred outside the categories or reporting procedures represented in the registry. The record does not provide further detail about how events were solicited, defined, assessed, or attributed. It also does not explain why the numbers at risk differ from the outcome-summary group sizes.

Zero recorded events is not proof of zero risk. The safety figures should be read as registry reports for this study, not as a comprehensive estimate of safety in other settings or populations.

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

The primary results describe a randomized comparison of a Facebook-based health-information intervention with an Attention-Control E-News condition. In the posted summaries, average self-reported cannabis-use days during the thirty-day period assessed three months after baseline were 18.0 in the intervention group and 14.9 in control. The simple unadjusted mean difference is 3.1 days, intervention minus control. The confidence interval includes zero, and the unadjusted p-value is 0.121, so the summary does not precisely establish the direction or size of a group difference.

This does not show that the intervention caused higher cannabis use, nor does it show that the groups were equivalent. The estimate is uncertain, and the sponsor’s separately reported standardized analysis differs from the simple recalculation. The registry record does not explain the methods needed to reconcile those results. Interpretation should keep these analyses distinct rather than treating either as a definitive answer to every question about the intervention.

The outcome concerns reported frequency during a particular thirty-day window. It does not measure all aspects of cannabis use, and it does not determine how use affected participants’ well-being, functioning, or safety. The secondary measures address some other perceptions and behaviors, but the available registry results are incomplete and multiple comparisons may affect how nominal findings should be weighed.

The record also leaves important questions open about missing data, analysis populations, intervention engagement, and longer-term outcomes. The trial results cannot establish effects beyond the participants and conditions studied. They do not support medical advice or a general conclusion about social media interventions. The appropriate interpretation is limited to the posted comparisons and their uncertainty.

18. Why This Trial Matters Statistically

This trial illustrates why statistical interpretation should start with the outcome’s scale and the estimand being compared. A difference in cannabis-use days is directly interpretable in the endpoint’s unit, while Cohen’s D expresses a standardized difference. Although these measures are related in principle, the registry’s reported sponsor analysis and the simple recalculation from posted means do not align numerically. Recognizing that distinction prevents an effect estimate from being read without attention to how it was produced.

It also shows why uncertainty matters alongside the observed group means. A difference of 3.1 days is a point estimate, not a precise statement about the underlying effect. The confidence interval crosses zero and covers possible differences in both directions. A p-value alone would not convey this range or establish equivalence.

Finally, the secondary outcomes and planning illustrations raise broader design questions. Multiple outcomes can create opportunities for chance findings, while planning requirements depend strongly on the effect a future study aims to detect. The registry provides hypothetical planning scenarios, but its original design assumptions are not reported. The record also lacks detail on missing data and analysis populations. These features make transparent reporting essential: statistical results are most useful when readers can connect estimates to prespecified questions, analysis methods, and the participants whose data contributed.

19. 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 registry record gives limited information about eligibility criteria and participant characteristics. The study focuses on emerging adults who use Facebook, but details needed to judge how closely the enrolled participants represent that population are not reported in the registry record. The Facebook intervention is described as a health-information page, while the control is described only as Attention-Control E-News; the content and relative intensity of the conditions are not detailed.

The primary endpoint is self-reported cannabis use during a thirty-day period, assessed at three months post baseline. Self-report and a single reporting window may not capture all aspects or patterns of use. The record does not report checks of measurement quality, corroborating measures, or outcomes beyond the specified assessment period. It also does not report intervention engagement or adherence.

The primary outcome summaries include fewer participants than the recorded enrollment, but the reasons and handling are not reported. Missing-data methods, analysis populations, baseline adjustment, and sensitivity analyses are also not reported in the registry record. These omissions make it difficult to assess the influence of incomplete data or analytical choices.

The sponsor’s reported standardized result differs from the simple unadjusted comparison of the posted summaries, and the registry does not provide enough detail to reconcile them. The record also names additional secondary outcomes without numeric results in the available information. Finally, multiplicity handling is not reported, limiting the strength of conclusions drawn from nominal secondary findings.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Social Media Intervention for Cannabis Use in Emerging Adults — NCT04187989.
• Registry record last updated 2022-02-11; status last verified 2022-01.
• Results first posted 2022-02-11.
• 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.

23. Record Summary

The registry describes a completed randomized, parallel-group study with no masking, comparing a Facebook social media intervention with Attention-Control E-News. Recorded enrollment is 149. The primary outcome is self-reported cannabis-use days during a thirty-day period at three months after baseline.

The posted primary means are 18.0 days for the intervention group and 14.9 for control. The unadjusted recalculation gives a mean difference of 3.1 days, with a confidence interval that crosses zero and p = 0.121. The sponsor separately reports a two-sided t-test of Cohen’s D of -.006, with a 95% confidence interval from -.478 to .466 and p = .980; the registry does not explain the difference between these analyses.

Secondary measures include perceived risk, peer approval or disapproval, impaired driving, and other drug use. Numeric results are not reported for every named outcome. The record reports zero serious adverse events, other adverse events, and deaths in both groups. Details on the original sample-size rationale, missing-data methods, analysis populations, and multiplicity handling are not reported in the registry record.