W-SUDs for COVID-19: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for W-SUDs for COVID-19 (NCT04460027), a randomized phase 1 study. The primary outcome is Change in Number of Substance Use Occasions in the Past 30 Days From Baseline to Post-treatment at 8 Weeks.

2. Clinical Question

The study was intended to test the comparative effect of a mobile-app-based substance use disorder program relative to a wait-list control. Its stated interests also included quality-of-life indices, retention, and engagement during the pandemic. The primary endpoint is narrower: it records change in the number of occasions, rather than a broader measure of substance-related harm or functioning.

The displayed estimates describe the groups’ average changes and their contrast. They do not, by themselves, reveal how individual participants changed, how use was distributed across participants, or whether the experience of using the program was similar across the intervention group. Those details are not reported in the registry record. The results therefore address a specific group-level question over the stated follow-up period, rather than every aspect of substance use or the program’s acceptability.

3. Trial Design

The registry record describes a randomized, double-masked, parallel-group Phase 1 study. Its listed enrollment is 180, and its status is completed. The study began on 2020-06-22, with primary completion on 2020-11-30. The sponsor is Woebot Health. The record identifies substance use disorders and alcohol use disorder as conditions under study.

Participants were assigned to W-SUDs or a wait-list control. The intervention was named Woebot Substance Use Disorder and was described as a mobile-app-based program. The registry’s brief summary says the study would compare its effect on substance use with the wait-list condition and explore differences in quality-of-life indices, retention, and engagement. Detailed descriptions of the two arms are not reported in the registry record.

The primary outcome is change from baseline to post-treatment at 8 weeks in the number of substance-use occasions in the past 30 days. The posted group summaries include 71.0 participants for W-SUDs and 81.0 for wait-list control. These are the group counts attached to the primary outcome results; the registry record does not explain how they relate to the listed enrollment of 180 or describe missing outcome data.

The study is labeled Phase 1. The registry record does not report the original sample-size justification, the allocation ratio planned by the investigators, the masking procedures, an interim-analysis plan, or the full statistical analysis plan. Randomization and masking are design labels, not evidence by themselves that allocation was concealed or that masking remained intact. Details needed to assess those procedures are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

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 Change in Number of Substance Use Occasions in the Past 30 Days From Baseline to Post-treatment at 8 Weeks, measured over Change from Baseline to Post-treatment at 8 weeks.

The primary endpoint measures change in the number of substance-use occasions during the past 30 days, from baseline to post-treatment at 8 weeks. It is a continuous measure summarized by group mean and standard deviation, with the unit recorded as occasions. A negative change represents a lower reported count at follow-up than at baseline; the endpoint is therefore expressed as change rather than as the follow-up count alone.

This outcome is used to quantify the frequency of substance use over a defined recall period. Comparing change between randomized groups asks whether their average trajectories differed over the study period, rather than simply asking which group had the lower follow-up value. The group summaries report mean changes of -9.1 for W-SUDs and -4.7 for wait-list control. The posted unadjusted contrast is -4.4 occasions, with a confidence interval from -4.914 to -3.886.

The measure captures frequency, not every dimension of substance use. It does not, on its own, identify the substance involved, the quantity used on each occasion, or the consequences of use. The registry record does not report the instrument or detailed rules used to define and count an occasion. Nor does it report a threshold for what would constitute an important change to participants. Interpretation should therefore stay close to the recorded measure: average change in occasions over the stated 30-day period.

7. Results Posted in the Registry

• W-SUDs: mean -9.10 versus -4.70 on control; difference -4.40 (95% CI -4.91 to -3.89), standardized effect d = -2.84; z-test p = <0.001.

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.

Change in Short Inventory of Problems - Alcohol and Drugs (SIP-AD) From Baseline to Post-treatment at 8 Weeks

• 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:
  • W-SUDs: mean -5.30 versus -4.70 on control; difference -0.60 (95% CI -0.94 to -0.26), standardized effect d = -0.57; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for W-SUDs than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Change in Drug Abuse Screening Test (DAST-10) From Baseline to Post-treatment at 8 Weeks

• 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:
  • W-SUDs: mean 1.30 versus 2.20 on control; difference -0.90 (95% CI -1.52 to -0.28), standardized effect d = -0.46; z-test p = 0.004.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for W-SUDs than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Change in Brief Situational Confidence Questionnaire (BSCQ) From Baseline to Post-treatment at 8 Weeks

• 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:
  • W-SUDs: mean 11.80 versus 5.30 on control; difference 6.50 (95% CI 5.46 to 7.54), standardized effect d = 2.00; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for W-SUDs than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The posted secondary outcomes cover several related but distinct domains: substance-related problems, drug screening, situational confidence, craving, pain, depression symptoms, anxiety symptoms, and pandemic impact. The registry record lists 12 secondary outcomes as posted, while the study record identifies 13 outcome measures overall. These measures broaden the description beyond the primary count of use occasions, but they do not measure the same construct.

The posted group summaries for the secondary outcomes include changes in both directions across measures. The three outcome comparisons with estimates and unadjusted p-values in the registry record include differences for substance-related problems, drug screening, and situational confidence. The overall pattern can be considered alongside the primary contrast, but these additional measures do not independently establish the primary result or explain why the primary groups differed. The registry record does not report analysis results for the other listed secondary outcomes.

Secondary outcomes often serve to explore whether a result is accompanied by changes in related experiences or measures. Their interpretation is more tentative when many outcomes are examined. In general, making multiple statistical comparisons increases the chance that at least one result appears statistically notable by chance if no adjustment or prespecified hierarchy is used. The registry record does not report a multiplicity procedure, a hierarchy among outcomes, or a statistical analysis plan that would clarify how these comparisons were intended to be interpreted.

The posted secondary comparisons are unadjusted recalculations from summary statistics, and the registry record lists no reported analyses for these outcomes. Their p-values should therefore not be treated as confirmatory evidence in the same way as a prespecified primary analysis. They are descriptive signals that may inform questions for future research, subject to the measurement, missing-data, and multiplicity limitations. No clinical interpretation threshold is reported for these outcomes, so the numerical differences do not alone establish practical importance.

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

• Change in Short Inventory of Problems - Alcohol and Drugs (SIP-AD) From Baseline to Post-treatment at 8 Weeks
• Change in Drug Abuse Screening Test (DAST-10) From Baseline to Post-treatment at 8 Weeks
• Change in Brief Situational Confidence Questionnaire (BSCQ) From Baseline to Post-treatment at 8 Weeks
• Change in Craving Ratings From Baseline to Post-treatment at 8 Weeks
• Change in Pain Ratings From Baseline to Post-treatment at 8 Weeks
• Change in Patient Health Questionnaire-8 (PHQ-8) From Baseline to Post-treatment at 8 Weeks
• Change in General Anxiety Disorder (GAD-7) From Baseline to Post-treatment at 8 Weeks
• Change in CAIR Pandemic Impact Questionnaire (CAIR-PIQ) From Baseline to Post-treatment at 8 Weeks

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is a continuous measure, and the registry reports it as a mean change with a standard deviation for each group. A mean gives the average change across the participants contributing to that group’s posted summary. A standard deviation describes how dispersed individual changes are around the group mean. It is not the same quantity as the uncertainty around the mean or around the difference between groups.

What does the mean difference represent?

The posted mean difference is -4.4 occasions. It compares the mean change in W-SUDs with the mean change in wait-list control, with the W-SUDs mean first. A negative contrast indicates that the intervention group’s average change was more negative. Here, the group means are -9.1 and -4.7, respectively. This is a comparison of group averages; it does not mean every participant changed by the group average or by the amount of the contrast.

The difference and its interval are recalculated, unadjusted comparisons based on the posted summary statistics. Such a calculation does not incorporate covariate adjustment, a repeated-measures model, or other features that might be part of an investigator’s planned analysis. Those details are not reported in the registry record. The posted p-value is also unadjusted. It should not be read as evidence that the study accounted for multiple outcomes or multiple statistical tests.

What does a p-value say?

In general, a p-value describes how unusual data at least as incompatible with a specified null model would be if that model and the test assumptions held. It is not the probability that the null hypothesis is true, and it is not a measure of the size or importance of an effect. The primary result has p < 0.001 in the posted comparison. That value should be read alongside the estimated difference and confidence interval, not as a standalone conclusion.

Because the result is an unadjusted recalculation from group summaries, its test assumptions may not match an analysis chosen in the trial’s protocol. The exact analysis model and any prespecified adjustment are not reported in the registry record. If the trial team conducted a different analysis, that result would need to be considered on its own terms; the registry record does not list a formal primary analysis result.

Why does randomization matter?

In general, random assignment aims to make comparison groups similar on average in factors known and unknown at the time of assignment. It supports interpreting group contrasts as effects of assignment when the randomization is properly implemented and other assumptions are reasonably met. The registry record identifies the design as randomized, but details of sequence generation, allocation concealment, adherence, and analysis population are not reported in the registry record. Randomization should not be treated as proof that all possible biases were eliminated.

The record also labels the trial double-masked. In general, masking can reduce the influence of expectations on care, participant reporting, and assessment. The record does not identify who was masked or describe how masking was maintained. That matters especially when the outcome relies on participant reports, but the registry entry does not give enough procedural detail to assess the masking implementation.

How should the effect size be understood?

The standardized effect estimate listed for the primary comparison is d = -2.84. A standardized effect expresses a difference relative to a measure of variability, making it scale-free in a way that the difference in occasions is not. Its size depends on how the standard deviation is calculated and on the data and summary method used. It does not replace the original-unit difference, and it does not indicate clinical importance on its own. The registry record does not report a threshold for a meaningful change.

General statistical caution applies when interpreting very large standardized effects from a single study, particularly when the trial is an early-phase study and the registry record does not describe the original design assumptions or a prespecified analysis. Such estimates can be sensitive to the study sample, measurement, and variability. The figures are best read as descriptions of the posted sample, not as guaranteed values for future studies.

What is not documented?

The registry record does not report the planned sample-size justification, original power assumptions, interim analyses, analysis populations, handling of missing outcomes, or a detailed statistical analysis plan. It also does not list reported inferential analyses for the posted secondary outcomes. These omissions do not establish what investigators did or did not do; they mean the relevant procedures cannot be assessed from the registry record. General explanations of statistical concepts do not fill in those trial-specific details.

11. Confidence Intervals and Precision

The primary mean difference is -4.4 occasions, and its 95% confidence interval runs from -4.914 to -3.886. In general, a confidence interval is a range of estimates compatible with the data and the method used to calculate it. Under repeated use of the same procedure and its assumptions, intervals at this stated confidence level would cover the target parameter at the corresponding long-run rate. It is not a probability statement that this particular interval contains the true value.

The interval is relatively narrow around the posted estimate and does not include zero. This conveys statistical precision for the simple unadjusted comparison: the estimate is not equally compatible with a zero contrast under the calculation used. The interval’s bounds are statistical uncertainty limits, not the full range of possible effects in other populations, nor a prediction interval for individual participants.

Precision depends on the amount and variability of the data and on the analysis assumptions. The primary outcome summaries include 71.0 participants in W-SUDs and 81.0 in wait-list control. The registry record does not report why these outcome counts differ from the listed enrollment, how missing observations were handled, or whether the outcome analysis included every randomized participant. Those omissions make it difficult to assess whether the interval reflects all relevant uncertainty from the trial’s conduct.

The confidence interval also says nothing by itself about whether a difference of this size matters to participants. The registry record does not report a minimally important difference or an interpretation threshold for the occasions measure. Precision around an estimate and clinical importance are separate questions. A narrow interval can describe the numerical contrast closely while leaving its practical meaning uncertain.

Finally, the interval comes from a recalculated, unadjusted comparison of posted summaries. A different prespecified model or missing-data method could yield a different estimate or interval. The registry record does not provide enough detail to compare such analyses. The reported interval is therefore useful for understanding the posted summary contrast, but should not be mistaken for a complete accounting of every source of uncertainty.

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 figures are illustrations based on the observed effect, not the trial’s original design calculation. For these continuous outcomes, the figures are participants per arm, rather than a total number across both groups or a count of events. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect targeted in each illustration is the stated fraction of the observed effect.

The 80% power column gives the illustrative number of participants per arm for a design with an 80% chance of detecting the specified effect under those assumptions, if that effect and the calculation model were correct. The 90% power column gives the corresponding number for a 90% chance. Power is a property of a planned study under assumptions; it is not the probability that a particular study result is true.

For the primary outcome, the illustrations use 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. The corresponding participants-per-arm values are 2 and 3, 4 and 5, and 8 and 11 for the 80% and 90% power targets, respectively. These small values are a mathematical consequence of basing planning on the large observed standardized difference; they should not be read as a recommendation for a future trial.

Smaller effects are harder to distinguish from random variation, so planning for a smaller fraction of the observed effect requires more participants. The illustrations are not observed power: they do not assess the probability that the completed trial detected its true effect. They are sensitive to the observed estimate, which can be unstable, particularly when it comes from a single study. The original trial’s sample-size justification and assumptions are not reported in the registry record.

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 = -4.400; pooled standard deviation σ = 1.549.
2. n = 2 × (1.96 + 0.842)² × 1.549² / -4.400² = 1.9, rounded up to 2 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 <- -4.4                      # observed difference in means
sigma <- 1.54919333848297                     # 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(4460027)
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 = 2 (80% power), 3 (90% power)
 75% of observed effect: n per arm = 4 (80% power), 5 (90% power)
 50% of observed effect: n per arm = 8 (80% power), 11 (90% power)
power.t.test: 3.2 
Simulated power at n = 2 per arm: 0.358 (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. Multiplicity, Missing Data and Analysis Populations

The registry record describes one primary outcome and several secondary outcomes. It lists 12 posted secondary outcomes, including measures of problems related to alcohol and drugs, drug screening, confidence, craving, pain, depression symptoms, anxiety symptoms, and pandemic impact. Considering many outcomes creates a multiplicity issue: in general, the more tests conducted, the greater the chance of seeing one or more apparently unusual results by chance. A prespecified testing order or adjustment can address that issue, but the registry record does not report such a plan or procedure.

The posted comparisons for the secondary outcomes are unadjusted recalculations. Their p-values do not account for the number of outcomes or tests. The registry record does not list reported inferential analyses for the secondary endpoints, and it does not provide a complete statistical analysis plan. It is therefore not possible to determine from the record which secondary tests, if any, were prespecified as confirmatory, whether additional outcomes were analyzed, or how results were selected for reporting.

Missing-data handling is also not reported in the registry record. The primary endpoint summaries include 71.0 participants in W-SUDs and 81.0 in wait-list control, while listed enrollment is 180. These registry entries alone do not explain the difference in counts: the record does not describe the analysis population, the number with missing outcomes, reasons for missingness, or any imputation or sensitivity analyses. The endpoint counts should not be assumed to represent all randomized participants.

Randomization supports a between-group comparison, but missing outcome data can undermine comparability if missingness is related to treatment assignment, outcomes, or participant characteristics. In general, the consequences depend on why data are missing and on the methods used. Without the trial’s missing-data approach and analysis populations, the robustness of the posted estimates to incomplete follow-up cannot be evaluated. The registry record also does not report whether the primary comparison followed an intention-to-treat principle.

These are reporting gaps, not proof that appropriate methods were absent. They limit what can be concluded from the registry record about multiplicity control, missing observations, and the set of participants represented by the analyses.

15. 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.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: hospitalization (1.1%).

The safety record lists 88 participants at risk in W-SUDs and 92 in wait-list control. It reports zero serious adverse events in W-SUDs and one in wait-list control. The serious event term recorded is hospitalization, with 1.1% listed. No other adverse events and no deaths are reported in either group.

These counts describe what the registry record reports; they do not establish that no unreported events occurred. The safety denominators differ from the participant counts attached to the primary outcome, and the record does not explain the relationship between those populations. It also does not give the event’s timing, clinical details, or enough information to assess the basis for attribution. The record reports zero serious events marked as related in W-SUDs and one in wait-list control, but the event description itself is limited to hospitalization.

Rare events are difficult to compare reliably in a study of this size and duration. In general, an absence of recorded events in one group does not establish an absence of risk, and a single event does not establish a group difference. The safety figures should be read as descriptive counts from the registry record, not as a definitive comparison of safety between groups.

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

The primary posted result is a between-group difference in average change in substance-use occasions over the 8-week period. W-SUDs participants had a mean change of -9.1, and wait-list participants had a mean change of -4.7. The unadjusted difference is -4.4 occasions, with a 95% confidence interval from -4.914 to -3.886 and p < 0.001. This describes a larger average decrease in the intervention group within the posted outcome summaries.

The result does not mean that every participant reduced use, that the same change occurred for every substance, or that changes persisted after the recorded follow-up. The outcome measures occasions in a past-30-day period; it does not, by itself, measure quantity, severity, consequences, or other aspects of recovery. The registry record does not report a threshold for a clinically important change, so statistical evidence of a group difference should not be equated with a judgment about its importance to participants.

The record identifies the study as randomized and double-masked, but does not give sufficient details to evaluate how those procedures were implemented or maintained. It also does not report the original analysis plan, analysis populations, missing-data approach, or a formal primary analysis in the posted analyses listing. The displayed contrast is an unadjusted recalculation from group summaries. These limitations make it important not to treat the recalculation as a complete substitute for the trial’s prespecified analysis.

The study was conducted during the COVID-19 pandemic, and the stated purpose concerns adults during that period. The findings do not on their own establish how the intervention would perform in other settings, populations, or periods. Nor do they isolate which program features might relate to the observed difference. The registry record describes a mobile-app program but does not report detailed engagement or retention results in the posted outcomes.

Accordingly, the posted data support a statistical description of the observed group contrast at the specified endpoint and follow-up. They do not settle questions about longer-term outcomes, individual response, implementation, comparative effects against other interventions, or practical significance.

17. Why This Trial Matters Statistically

This trial illustrates the distinction between a numerical result and the strength of the inferences that can be drawn from it. The primary comparison is expressed in the original outcome unit, occasions, and is accompanied by a confidence interval. That makes it possible to consider both the estimated magnitude and its statistical uncertainty rather than relying on a p-value alone.

It also shows why registry reporting details matter. The study is labeled randomized and double-masked, but the registry record does not report the operational details of those procedures, the original sample-size rationale, or the full analysis plan. Without that information, readers cannot fully assess whether the posted summary comparison corresponds to the planned primary analysis or how the analysis handled incomplete outcomes.

The range of secondary measures is statistically informative as a reminder that a trial may assess many related but nonidentical outcomes. A pattern across outcomes can help frame further questions, but unadjusted comparisons across multiple endpoints carry greater risk of chance findings and should not be read as independent confirmation. Distinguishing a prespecified primary result from exploratory secondary signals is central to sound interpretation.

The planning illustrations further demonstrate how estimated effect size influences sample-size calculations. Because the illustrations are based on the observed effect, they are not evidence that the completed study was adequately powered and should not be used as the trial’s original justification. Planning around a smaller effect requires more participants under the stated assumptions, while the observed estimate may not reliably represent an effect expected in future work.

Finally, the safety counts reinforce that descriptive event reporting is not a precise comparative safety analysis. Rare events and limited follow-up require cautious interpretation. Together, these issues make the record useful for statistical reading while underscoring the value of transparent protocols, complete outcome reporting, and clearly documented analysis decisions.

18. 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.

Several limitations are specific to the information recorded for this trial. The posted arm descriptions are blank, and the brief summary does not provide detailed eligibility criteria, intervention content, or wait-list procedures. The registry record therefore gives limited context for understanding what participants experienced beyond the mobile-app delivery and control label.

The primary result is available as a group-level summary and an unadjusted recalculation. No individual participant data, distributional plots, baseline outcome summaries, or detailed primary-analysis results are reported in the registry record. The mean and standard deviation do not show whether the outcome was skewed, whether a small number of observations strongly influenced the mean, or how change varied across participants.

The number of participants attached to the primary outcome results is 71.0 for W-SUDs and 81.0 for wait-list control, while listed enrollment is 180. The registry record does not explain the difference, report the outcome completion pattern, or describe missing-data methods. The extent to which attrition or incomplete measurement could affect the comparison cannot therefore be assessed from the posted record.

The registry record does not report the original sample-size justification, detailed masking procedures, allocation concealment, the statistical analysis plan, or any interim-analysis plan. It also does not report a multiplicity adjustment or establish which secondary outcomes were intended to be confirmatory. The secondary outcome record is incomplete in the sense that 12 are posted, while the analysis listings do not report inferential analyses for them.

The follow-up is limited to post-treatment at 8 weeks in the primary outcome description. Longer-term results are not reported in the registry record. The primary count reflects occasions, not quantity or severity, and no meaningful-change threshold is documented. These reporting and measurement limitations constrain clinical interpretation without negating the numerical group contrast.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: W-SUDs for COVID-19 — NCT04460027.
• Registry record last updated 2022-12-21; status last verified 2022-11.
• Results first posted 2022-12-21.
• 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.

22. Record Summary

NCT04460027, titled “W-SUDs for COVID-19,” is a completed Phase 1 randomized, double-masked, parallel-group study sponsored by Woebot Health. Listed enrollment is 180. The study compared the Woebot Substance Use Disorder mobile-app program with a wait-list control during the COVID-19 pandemic.

The primary outcome was change from baseline to post-treatment at 8 weeks in the number of substance-use occasions in the past 30 days. Posted mean changes were -9.1 for W-SUDs and -4.7 for wait-list control. The unadjusted mean difference was -4.4 occasions, with a 95% confidence interval from -4.914 to -3.886 and p < 0.001.

The registry record also lists secondary outcomes and safety counts. It does not report the original sample-size justification, a detailed statistical analysis plan, analysis populations, or the missing-data approach. The posted primary contrast is a recalculation from summary statistics and should be interpreted with those reporting limitations in mind.