Clinical Neurobiology of Serotonin and Addiction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Clinical Neurobiology of Serotonin and Addiction (NCT00732901), a randomized phase 2, phase 3 study. The primary outcome is Immediate Memory Task.

2. Clinical Question

The registry record describes a study of serotonin function, impulsivity, and cue reactivity in people with cocaine dependence and healthy controls. It also describes examining effects of escitalopram and mirtazapine on impulsivity and cue reactivity in human cocaine users. The listed interventions for the randomized comparison are escitalopram and placebo; mirtazapine is mentioned in the study summary but is not listed as an intervention in the record.

The study was registered as randomized and parallel, but the registry record does not provide the primary outcome results or an inferential analysis. Therefore, the record alone cannot establish the direction, size, or precision of an escitalopram–placebo difference on the stated measure.

3. Trial Design

The registry record identifies this as a randomized, parallel-group study with quadruple masking and phase designations of phase 2 and phase 3. It lists an enrollment of 160 and a completed status. The sponsor is Virginia Commonwealth University. The record lists cocaine dependence as a condition.

Escitalopram and placebo are the listed interventions, with one arm described as escitalopram and the other as placebo. The primary outcome assessment is described as occurring after an acute dose and after chronic administration. The record does not report the dose, treatment duration, allocation ratio, sequence-generation method, concealment procedures, or the details of who was masked. Those design features should not be inferred from the labels alone.

The study summary gives broader aims: examining the relationship among 5-HT2R function, impulsivity, and cue reactivity in cocaine-dependent participants and healthy controls, as well as examining effects of escitalopram and mirtazapine in cocaine users. However, mirtazapine is not among the interventions or arms listed in the record. The registry record does not explain this difference between the summary and the listed randomized comparison, nor does it describe how healthy controls fit into the reported arms.

Attentional bias measured by the Cocaine Stroop Task and cocaine-positive urines are listed as secondary outcomes. The record lists three outcome measures but does not provide numerical primary-outcome values. It reports no analyses in the posted results. Although the record gives a completed status, it does not report enough information to reconstruct the conduct, follow-up, or analyzed populations for the primary comparison.

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.

Before assignment: The enrollment number was the number of participants who signed the informed consent. The Participants who Started in the Participant flow module were number of participants who completed the screening and met inclusion criteria to start medication.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Numerical data values are not accessible because PI transferred institutions. See references.

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 Immediate Memory Task, measured over after acute dose and after chronic administration.

The primary endpoint is Immediate Memory Task (IMT) commission errors to catch stimuli. The task is described as a continuous performance test: participants respond when a five-digit target matches the preceding stimulus, while a catch stimulus differs slightly from the preceding number. A response to a catch stimulus is counted as a commission error, also described as a false alarm.

The endpoint is expressed as the percentage of overall responses to a catch stimulus that were commission errors, on a scale from 0 to 100. The registry record describes zero as no impulsive responses and 100 as all responses being impulsive. This makes the measure a behavioral indicator of impulsivity in the task, rather than a direct measure of all forms of impulsive behavior.

The endpoint is used because the study aims include assessing impulsivity and examining whether escitalopram is associated with a change in this task-based measure. The listed assessment period includes after an acute dose and after chronic administration. The registry record does not give separate values for these assessment points, specify the exact scoring data available for analysis, or report a treatment contrast. Numerical data values are stated to be inaccessible because the principal investigator transferred institutions.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies randomization, quadruple masking, and a parallel-group model. These labels describe broad design features, but they do not provide the operational details needed to assess how the allocation was generated, concealed, or implemented. The record does not report those methods, the allocation ratio, or the specific people covered by quadruple masking.

What does randomization contribute?

In general, randomization assigns participants to study groups using a chance-based process. When implemented and preserved appropriately, it can reduce systematic differences between groups at the start of a study. That benefit does not guarantee balance in every characteristic, nor does the label alone establish that allocation was adequately concealed. The registry record does not give the methods needed to evaluate these details.

A parallel-group design generally means participants are assigned to a group and assessed in that group rather than being assigned to receive each intervention in sequence. In this record, the listed arms are escitalopram and placebo. The registry record does not describe crossover, treatment switching, or the schedule and duration of treatment, so such features should not be presumed.

How should the primary endpoint be understood?

The IMT is described as a continuous performance test, and the primary measure is the percentage of responses to catch stimuli that are commission errors. In general, a percentage score summarizes the frequency of a specified response relative to the relevant response set. The endpoint is task-specific: it reflects false alarms under the task instructions and is used as a measure of impulsivity in this study. The measure does not, by itself, summarize all dimensions of impulsivity or establish a mechanism involving serotonin.

The record names assessment after an acute dose and after chronic administration. In general, repeated assessments can address whether an outcome differs across treatment periods or changes over time. They also create choices about which time point is primary, whether each is analyzed separately, and whether repeated observations are modeled jointly. The registry record does not report those analysis decisions, the numerical measurements, or a single comparison selected from the stated categories or time points.

What can be inferred from the posted results?

The primary outcome values are not accessible because the record says the principal investigator transferred institutions. The registry record reports no analyses. Consequently, there is no posted primary estimate from which to assess direction, magnitude, or uncertainty, and no basis for a recalculation from summary statistics. In general, a treatment-effect estimate describes the contrast between groups under a specified analysis; a confidence interval conveys its precision, while a p-value summarizes compatibility with a null hypothesis under the model. None of these primary-outcome statistics is reported in the registry record.

The record notes that the outcome has several categories or time points and was not reduced to one comparison. In general, examining multiple outcomes or time points can raise multiplicity concerns: the chance of at least one apparently notable result may increase when many tests are considered. Prespecified outcomes and a stated adjustment or interpretation strategy help readers understand such testing. The registry record does not report a multiplicity strategy or identify a single primary contrast for the listed assessment periods.

General statistical models also depend on the form of the outcome and the assumptions made about its distribution. A percentage score is bounded, so an analyst would need to consider whether the chosen model fits the observed data and whether its assumptions are reasonable. This is a general methodological consideration, not a description of the analysis used in this study: the statistical model and diagnostics are not reported in the registry record.

What is a planning illustration?

Sample-size calculations can illustrate how many participants per arm might be needed under specified assumptions about the effect to detect, significance level, allocation, and statistical model. Such calculations are planning illustrations, not observed power and not evidence that a study did or did not detect an effect. The registry record does not provide a trial-specific sample-size justification or the assumptions needed to evaluate one. No sample-size illustration can substitute for the missing endpoint values and analysis.

Finally, interpretation depends on who was included in each analysis and how missing measurements were handled. General approaches can include analyzing participants according to randomized assignment or using a defined subset with observed outcomes, but those choices answer different questions and can be affected by missingness. The registry record does not report the primary analysis population, exclusions, missing-data methods, or sensitivity analyses. These omissions prevent a full assessment of the statistical methods and the robustness of any treatment comparison.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome description includes assessments after an acute dose and after chronic administration. The registry record states that the primary outcome has several categories or time points and was not reduced to one comparison. It does not identify a single primary time point or contrast, give separate numerical results for the assessment periods, or describe how multiple comparisons were handled.

Attentional bias measured by the Cocaine Stroop Task and cocaine-positive urines are listed as secondary outcomes. The study summary also refers to cue reactivity and broader relationships involving 5-HT2R function. In general, testing several outcomes or time points raises a multiplicity issue because the interpretation of individual findings depends on how many comparisons were planned and how they were selected. The registry record does not report a multiplicity adjustment, a hierarchy of outcomes, or a prespecified strategy for interpreting multiple results.

The primary outcome values are described as inaccessible because the principal investigator transferred institutions. The record reports no analyses. It does not report the number of participants with available primary outcome measurements, exclusions from analysis, reasons for missing data, or methods for handling missing measurements. It also does not describe an intention-to-treat population, a per-protocol population, or another analysis population. These details are not reported in the registry record.

As a result, the posted information does not allow assessment of whether missingness differed between arms, how it may have affected estimates, or whether alternative assumptions were tested. This is a limitation in evaluating both multiplicity and the reliability of any analysis, not evidence that a particular method was or was not used.

11. Safety Results

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

Other (non-serious) adverse events

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

The registry record lists serious adverse events for the escitalopram arm as 0 affected among 11 at risk, and for the placebo arm as 0 affected among 12 at risk. For other adverse events, it lists 0 affected among 11 at risk in the escitalopram arm and 0 affected among 12 at risk in the placebo arm. No serious adverse event terms are listed.

These figures describe the adverse-event entries in the registry record. They should not be treated as primary-outcome results or as a comparison of impulsivity. The record does not explain how the adverse-event groups relate to the enrollment entry, give the observation period for these figures, or provide event-level detail. Death counts are not reported in the registry record.

Zero recorded affected participants in these entries means that no affected participants are listed for the stated groups in the posted adverse-event data. It does not establish that no events occurred outside the reporting represented by these entries, and it does not by itself establish comparative safety. The registry record does not provide enough detail to assess completeness of safety follow-up or the precision of a safety comparison.

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

The record establishes that a randomized, parallel-group study listed escitalopram and placebo and identified IMT commission errors to catch stimuli as its primary measure of impulsivity. It also gives a broad study rationale involving serotonin function, impulsivity, cue reactivity, cocaine dependence, and healthy controls. These registry entries describe the study question and structure, but they are not evidence of an observed treatment effect.

The numerical primary-outcome values are not accessible in the registry record, and the posted results report no analyses. Consequently, the record does not show whether IMT scores were higher or lower in either arm, whether any contrast was large or small, or how precisely a contrast was estimated. It does not support a conclusion that escitalopram changed impulsivity, or that it had no effect.

The primary outcome spans assessments after an acute dose and after chronic administration, and the registry record notes several categories or time points without reducing them to one comparison. In the absence of results and a stated analysis strategy, it is not possible to determine whether the intended question concerned one assessment, changes over time, or multiple separate comparisons.

The registry summary mentions mirtazapine and healthy controls, while the listed randomized arms contain escitalopram and placebo. The record does not explain how the broader aims relate to the listed treatment comparison. The secondary outcomes are named, but their numerical findings are not reported in the registry record.

The adverse-event entries list zero affected participants for serious and other events in the stated at-risk groups. These entries do not supply missing primary efficacy results and do not by themselves establish the completeness of safety reporting. Overall, the registry record permits a description of the planned research question and some design and safety fields, but not a quantitative assessment of the primary treatment comparison.

13. Why This Trial Matters Statistically

This study is statistically notable because the record combines a randomized, masked, parallel-group design with a task-based primary outcome, yet the numerical outcome values are inaccessible. The contrast between a defined measurement and missing results illustrates an important distinction: knowing what a trial intended to measure is not the same as having evidence that permits an effect estimate.

The endpoint is described in operational terms: commission errors to catch stimuli on the IMT, expressed as a percentage of responses to catch stimuli. That description helps readers understand what the measure represents and what it does not. It is a task-specific measure used as an indicator of impulsivity, not a direct summary of every aspect of behavior or of serotonin function.

The record also identifies multiple assessment periods and says the primary outcome was not reduced to one comparison. This highlights why analysis choices matter. When there are several times or outcome categories, readers need to know which contrasts were prespecified, whether each was analyzed separately, and how the resulting evidence was interpreted. Those details are not reported in the registry record.

Finally, the case shows why design labels cannot replace analysis reporting. Randomization and masking are relevant features, but they do not reveal the treatment effect, its uncertainty, or the impact of missing outcome data. The registry record’s completed status and enrollment entry cannot answer those questions. Transparent numerical results and methods would be required to evaluate the primary comparison statistically.

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 most consequential limitation is that numerical values for the primary outcome are not accessible. The registry record attributes this to the principal investigator transferring institutions. It reports no analyses, so there is no primary estimate, confidence interval, or p-value available for interpretation or recalculation.

The record identifies assessments after an acute dose and after chronic administration but does not report their separate results or explain how the several categories or time points relate to the primary comparison. The dose, treatment duration, and precise assessment schedule are not reported in the registry record. Nor does the record describe the statistical model, analysis population, missing-data approach, or sensitivity analyses.

The study summary refers to mirtazapine and healthy controls, but the listed randomized arms are escitalopram and placebo. The registry record does not explain the relationship between these broader aims and the listed arms. This limits the ability to characterize the full study structure from the available record.

Secondary outcomes are named, but their results are not reported in the registry record. The record also does not provide details of the allocation process, the practical implementation of quadruple masking, or the specific people masked. For safety, the record lists at-risk and affected counts but does not report death counts, event-level details, or the safety observation period. These omissions constrain evaluation of both the treatment comparison and the completeness of the record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Clinical Neurobiology of Serotonin and Addiction — NCT00732901.
• Registry record last updated 2019-03-08; status last verified 2017-06.
• Results first posted 2017-03-30.
• 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 record describes a completed randomized, quadruple-masked, parallel-group study with phase 2 and phase 3 designations, sponsored by Virginia Commonwealth University. It lists escitalopram and placebo as the randomized interventions and identifies IMT commission errors to catch stimuli as the primary measure of impulsivity.

The study summary describes broader aims concerning 5-HT2R function, impulsivity, cue reactivity, cocaine dependence, and healthy controls. Attentional bias measured by the Cocaine Stroop Task and cocaine-positive urines are listed as secondary outcomes. The record lists an enrollment of 160.

Primary numerical results are not accessible, and no analyses are reported. The adverse-event entries list zero affected participants in the stated groups; death counts are not reported in the registry record. The available record therefore describes the design and measurement but does not permit evaluation of the primary treatment effect.