Approach Bias Modification for the Treatment of Cannabis Use Disorder: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Approach Bias Modification for the Treatment of Cannabis Use Disorder (NCT03629990), a randomized na study. The primary outcome is Cannabis Approach Bias.

2. Clinical Question

3. Trial Design

The registry describes a randomized, quadruple-masked, parallel-group trial. Its enrollment field lists 104, and its status is completed. The recorded start date is 2019-01-16 and the primary completion date is 2023-10-30. The phase is listed as NA. The sponsor is the Medical University of South Carolina.

The active group is labeled Active ABM + CBT/MET. Participants receive approach bias modification training directed at cannabis cues and MET/CBT. The comparison group is labeled Sham ABM + CBT/MET. Its computerized tasks are similar, but do not manipulate response contingencies to target approach bias; participants also receive MET/CBT. Thus, the registered contrast concerns active versus sham ABM against a shared psychosocial therapy background.

Masking is recorded as quadruple, but the registry record does not identify which roles were masked or describe how masking was maintained or assessed. It also does not report the randomization procedure, allocation concealment, stratification factors, or the numbers assigned to each group. The safety record separately gives group-specific numbers at risk for adverse-event reporting; those figures should not be treated as a complete account of allocation or outcome follow-up.

The primary outcome population is specified as all randomized participants with at least one post-randomization visit. The record identifies assessments at baseline, end of treatment at 4 weeks, and follow-up at 8 weeks. It names Percent Days Using Cannabis and Marijuana Craving Questionnaire Total Score (Craving) as secondary outcomes, but their numerical results 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

Analysis population for the primary outcome, as defined in the registry: All randomized participants with at least one post randomization visit.

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: Baseline analysis population consists of all participants successfully randomized either active or sham condition.

6. Primary Endpoint

The registry lists the primary outcome as Cannabis Approach Bias, measured over Baseline, End of Treatment (4 weeks), Follow-Up (8 weeks).

The primary endpoint is cannabis approach bias, measured in seconds using a cue-reactivity task. Participants see cannabis-related and neutral images on a computer screen and move a joystick in response to a feature unrelated to image content. Pulling zooms the image in and pushing zooms it out, while reaction time is measured from image onset to the image moving off-screen.

The registry defines the bias score by subtracting reaction time for pulling in response to cannabis cues from reaction time for pushing in response to cannabis cues. A positive score therefore indicates greater approach bias toward cannabis cues under this measure. The recorded summary statistic is the mean, with standard deviation as the measure of dispersion.

Assessments are scheduled at baseline, end of treatment at 4 weeks, and follow-up at 8 weeks. A cue-reactivity task offers a behavioral measure of responses to drug-related cues, which fits the trial’s stated interest in approach bias as a possible treatment target. It is not, by itself, a measure of cannabis use or craving. Those are listed separately as secondary outcomes. The registry record does not report the observed endpoint values, changes over time, or a comparison between groups.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General statistical explanation: the endpoint is continuous because it is expressed as reaction time in seconds and summarized by a mean. The standard deviation describes participant-to-participant variability within a group. It is not the same as the uncertainty in a group mean or in a contrast between group means. Estimating a treatment contrast requires both the group data and a specified analysis; neither numerical contrast estimates nor inferential results are reported in the registry record.

What does randomization contribute?

In general, random allocation is intended to make treatment groups comparable with respect to measured and unmeasured factors at the point of assignment. It supports an interpretation of a between-group contrast as an effect of assignment when the trial is conducted and analyzed appropriately. Randomization does not guarantee that groups are identical, and it does not remove the need to describe missing observations, adherence, or the analysis population. The registry identifies the trial as randomized, but does not report the sequence-generation or allocation-concealment procedures.

What does masking contribute?

The record labels the trial quadruple-masked. In general, masking can reduce the influence of expectations on participant behavior, treatment delivery, outcome assessment, or analysis. The registry does not specify which parties were masked, what information they could access, or whether masking was evaluated. The label alone cannot establish how masking operated in practice.

How should a repeated endpoint be analyzed?

General statistical explanation: repeated measurements from the same participant tend to be related. An analysis that accounts for this relationship can use information across visits while representing within-person correlation. The scientific interpretation depends on the chosen contrast: a group comparison at end of treatment, a comparison at follow-up, and a treatment-by-time pattern are not interchangeable. Baseline, end of treatment at 4 weeks, and follow-up at 8 weeks are named for the primary endpoint, but the registry record does not report the model, contrast, covariate adjustment, or standard-error method used.

The outcome is defined as a difference between reaction times for pushing and pulling in response to cannabis cues. General statistical explanation: the direction of a signed score matters. The registry explicitly states that a positive value indicates greater cannabis approach bias. An estimated group contrast would need its direction and reference group stated clearly to avoid reversing the interpretation. No group contrast is posted in the registry record.

Why does uncertainty matter?

General statistical explanation: a point estimate gives a single best estimate under a chosen method, but it does not show how much uncertainty remains. A confidence interval conveys uncertainty around an estimate under the assumptions of the analysis. A p-value addresses compatibility of the data with a specified null hypothesis under a model; it does not quantify the clinical importance of a difference. For this trial, the registry record does not report an estimate, confidence interval, or p-value, so neither precision nor statistical significance can be assessed from the posted outcome information.

What can planning calculations say?

The record describes a planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It specifies that the effect to detect is a stated fraction of the observed effect. For time-to-event tables, the stated convention is total events using Schoenfeld; for other tables, it is participants per arm. These are planning assumptions, not a report of observed power. The registry record does not report the trial’s own sample-size justification, and no planning output values or observed primary effect are reported in the registry entries. A planning illustration cannot replace an estimate and uncertainty interval from the trial results.

General statistical explanation: over-dispersion is a concern when outcome variability is greater than a model assumes. If it is ignored, standard errors can be too small and inferential conclusions too confident. That issue is most directly relevant to count outcomes or models with a count-like response, rather than automatically to every continuous outcome. The registry does not report an over-dispersion assessment or a statistical model for the named secondary outcomes, so no trial-specific conclusion about it is possible.

10. Multiplicity, Missing Data and Analysis Populations

The record lists three outcome measures, including cannabis approach bias as the primary outcome and Percent Days Using Cannabis and Marijuana Craving Questionnaire Total Score (Craving) as secondary outcomes. It lists zero analyses. Numerical results and inferential tests for these outcomes are not reported in the registry record.

Multiplicity arises when several outcomes, time points, or contrasts are examined: the chance of at least one apparently unusual result can increase when many tests are considered. General statistical explanation: a prespecified primary comparison and an explicit multiplicity strategy help readers distinguish the main confirmatory question from secondary or exploratory analyses. The registry record does not report a multiplicity adjustment, a hierarchy of tests, or which time contrast was intended to be primary. The primary outcome description includes baseline, end of treatment at 4 weeks, and follow-up at 8 weeks, but does not specify how those assessments were combined for inference.

The outcome population is described as randomized participants with at least one post-randomization visit. The record does not report how many participants contributed to each endpoint or visit, reasons for missing data, or the method used to handle missing observations. It also does not report whether analyses followed an intention-to-treat approach, how adherence was handled, or whether sensitivity analyses were conducted. These details matter because an analysis restricted to observed visits can differ from one that makes explicit assumptions about unobserved outcomes.

The statistical analysis plan, covariate adjustment, interim analyses, and sample-size justification are not reported in the registry record. Their absence prevents evaluation of whether the reported analysis choices, if any, followed a prespecified plan.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

The adverse-event record lists 53 participants at risk in the Active ABM + CBT/MET group and 51 in the Sham ABM + CBT/MET group. It records zero serious adverse events and zero other adverse events in each group, and zero deaths in each group. No serious adverse-event terms are listed.

These are counts as recorded for the safety entries. A zero count means that no event in that category is recorded in the registry entry; it does not establish that no symptoms or events occurred outside the registry’s definitions, collection period, or reporting process. The record does not describe the adverse-event collection window, event definitions, severity grading, attribution procedures, or completeness of follow-up. Those details are needed to interpret how broadly the counts capture safety information.

The numbers at risk in these safety entries should be read with their stated context. They are not a substitute for the primary-outcome population definition, and the registry record does not explain any difference between safety denominators and the numbers contributing to outcome analyses. These figures describe recorded events; they do not by themselves establish comparative safety or rule out uncommon harms.

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

The registry record establishes that a randomized, quadruple-masked, parallel-group study was completed and that its primary outcome was cannabis approach bias measured in seconds. It describes active ABM and sham ABM, with MET/CBT in both groups, and specifies the assessment schedule. It also identifies cannabis use and craving as secondary outcomes.

What the record does not provide is the numerical outcome information needed to judge the observed effects. There are no reported group summaries, treatment contrasts, confidence intervals, or test results for the primary outcome or named secondary outcomes. The record lists zero analyses. As a result, the direction, size, and precision of the treatment comparison cannot be established from this registry record.

General statistical explanation: an intervention can be tested against a comparator without the result being interpretable from design information alone. Randomization and masking describe features of trial conduct; they do not reveal the outcome estimate. Likewise, an outcome definition explains what was measured, not what the measurements showed. A completed status indicates that the registry’s trial status is completed, not that a particular treatment effect was demonstrated.

The endpoint concerns reaction-time bias toward cannabis cues, not cannabis consumption itself. Even a reported difference on that measure would not automatically answer whether cannabis use or craving differed; those are listed separately. Similarly, a statistical difference, if one were reported, would need its magnitude and uncertainty considered before judging its importance. No treatment recommendation or efficacy conclusion follows from the information recorded.

The safety entry reports zero serious events, zero other events, and zero deaths in each group, using its stated at-risk counts. Those entries are informative as recorded, but the missing details about ascertainment and follow-up limit the safety interpretation. The most defensible reading is therefore that the registry documents a completed trial design and measurement plan, while the posted record does not supply results adequate to characterize efficacy or precision.

13. Why This Trial Matters Statistically

This trial addresses an explicitly stated statistical question: whether training aimed at modifying approach bias can change a behavioral measure of responses to cannabis cues beyond a sham task, when MET/CBT is received in both groups. The shared therapy background makes the registered comparison focused on active versus sham ABM, rather than on psychosocial therapy versus no therapy.

The primary endpoint is a constructed reaction-time score, and its sign has a defined interpretation: positive values indicate greater cannabis approach bias. That definition is important because a contrast can be misread if the score’s direction or group reference is unclear. The registry also schedules repeated assessment at baseline, end of treatment at 4 weeks, and follow-up at 8 weeks, raising the statistical issue of how change over time should be represented.

General statistical explanation: behavioral measures can offer a way to study a proposed mechanism, but a measure of a mechanism is not interchangeable with a clinical outcome. Separate outcome measures for cannabis use and craving allow distinct questions to be considered, provided their results and analysis plans are reported. The record lists these secondary outcomes but does not report their results.

For biostatistical interpretation, the key point is the difference between a well-described design and an assessable result. Randomization, masking, a prespecified-looking outcome definition, and a stated follow-up schedule are not enough to evaluate an effect without estimates and uncertainty. The registry record’s lack of numerical analyses means the main comparison’s magnitude and precision remain unknown in this record.

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 primary limitation for interpretation is that the registry record does not report numerical results for the primary endpoint or the named secondary outcomes. It lists zero analyses. Without group summaries, treatment contrasts, or uncertainty measures, the observed effect and its precision cannot be assessed.

The record does not report the detailed statistical plan, including the model for repeated measurements, the target time contrast, covariate adjustment, handling of missing data, multiplicity procedures, or any interim analyses. It does not report outcome-specific denominators or reasons for missing visits. Although the primary outcome population is described as randomized participants with at least one post-randomization visit, the record does not explain how that population was implemented in analysis.

Some trial conduct details are also absent. The registry identifies quadruple masking but does not specify the masked roles or how masking was maintained. It identifies randomization but does not report sequence generation or allocation concealment. Eligibility criteria and the detailed intervention schedule are not reported in the registry record.

The safety entries report no serious or other adverse events and no deaths in either group, but the registry record does not describe the event definitions, ascertainment window, or completeness of safety follow-up. Those omissions limit interpretation of the recorded counts. The planning assumptions describe an illustrative calculation based on the observed effect, but the record does not report a sample-size justification for the trial itself or a numerical observed effect on which to assess those calculations.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Approach Bias Modification for the Treatment of Cannabis Use Disorder — NCT03629990.
• Registry record last updated 2024-12-17; status last verified 2024-11.
• Results first posted 2024-12-17.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry lists NCT03629990 as a completed randomized, quadruple-masked, parallel-group trial sponsored by the Medical University of South Carolina. Enrollment is listed as 104. The recorded start date is 2019-01-16, and the primary completion date is 2023-10-30. Phase is listed as NA.

The trial compares active approach bias modification plus MET/CBT with sham ABM plus MET/CBT for cannabis use disorder. Cannabis approach bias, measured in seconds with a cue-reactivity task, is the primary outcome. Assessments are scheduled at baseline, end of treatment at 4 weeks, and follow-up at 8 weeks. Percent Days Using Cannabis and Marijuana Craving Questionnaire Total Score (Craving) are listed as secondary outcomes.

The registry record lists zero analyses and does not report numerical outcome results. Its safety entries record zero serious adverse events, zero other adverse events, and zero deaths in both groups. The available record therefore describes the trial and its measures but does not allow estimation of the primary treatment contrast.