Nicotine Reinforcement and Aversion in Young Adult Light Smokers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Nicotine Reinforcement and Aversion in Young Adult Light Smokers (NCT01495819), a randomized early/phase 1 study. The primary outcome is DEQ - Pleasurable.

2. Clinical Question

3. Trial Design

NCT01495819, titled “Nicotine Reinforcement and Aversion in Young Adult Light Smokers,” is recorded as a completed, randomized, double-blind crossover study at Yale University. Its phase is listed as EARLY PHASE1. The registry records enrollment of 34 participants. The summary describes an intended study of nicotine self-administration among young adult light and intermittent smokers, with nicotine and saline conditions.

The study description lists five nicotine doses: 0.013, 0.025, 0.05, 0.1 and 0.2 mg/70 kg. It describes sampling the assigned nicotine dose and placebo, followed by the opportunity to choose between them over ten choices during a 150-minute period. The record also lists saline and nicotine as interventions. Although the model is identified as crossover, the detailed allocation sequence and how each participant moved through the dose conditions are not reported in the registry record.

The summary describes five experimental sessions. The primary-outcome population note states that 34 participants were randomized, that four did not complete all five test sessions, and that completed sessions were analyzed. It does not explain how incomplete sessions were handled in each analysis or how many observations contributed to the primary outcome.

The study summary describes threshold dose and dose-response slope as main outcomes, alongside nicotine intake, nicotine clearance and self-reported drug effects. The posted primary outcome is specifically the DEQ pleasurable-effects rating, on a scale from zero to 100 millimeters, with higher scores indicating greater perceived pleasure. That endpoint is therefore distinct from the broader self-administration questions in the study summary. The registry lists three outcome measures, but does not report numerical results for the primary endpoint.

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: Thirty four subject were randomized, 4 didn't complete all five test sessions, the sessions that were completed were analyzed.

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 DEQ - Pleasurable, measured over Up to 10 Minutes.

The primary endpoint is the pleasurable-effects subscale of the Drug Effects Questionnaire. It records participants’ ratings of how pleasurable the drug effect was, using a scale with a minimum of zero and a maximum of 100 millimeters. Higher scores indicate a more pleasurable rating. The timeframe is up to 10 minutes, and the registry describes the reported measure as a least-squares mean with standard error.

A subjective rating can describe an experienced effect that is not captured by a behavioral measure such as choosing to self-administer a dose. In this study, the rating is relevant to the broader interest in nicotine reinforcement and aversion, but it should not be treated as a direct measurement of nicotine choice, the threshold dose, or the dose-response slope. Those are separate questions in the study summary.

Least-squares means are model-based averages; their interpretation depends on the model and the observations included. The registry record does not report the model specification or numerical endpoint estimates. It also does not report a confidence interval or a test of the primary outcome. As a result, the endpoint’s scale and direction are interpretable, but the magnitude and precision of the observed ratings cannot be assessed from the reported primary-outcome information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a randomized, double-blind crossover design. Randomization concerns how study conditions are assigned; blinding is intended to limit the influence of knowledge about condition on participants’ reports or study conduct. A crossover design involves observations under multiple conditions within the same participant, but the registry does not give the detailed condition sequence or allocation procedure. It also does not report whether sequence, period or carryover effects were assessed.

What does a least-squares mean represent?

A least-squares mean is an average estimated from a statistical model rather than necessarily a raw arithmetic average. Depending on the model, it can account for specified design factors or other variables. The endpoint description identifies a least-squares mean and standard error, but the model specification and adjustment factors are not reported in the registry record. The value’s exact interpretation would therefore depend on details that are not available in the record.

A standard error describes the uncertainty of an estimated mean under the statistical model. It is not the same as the spread of individual participant ratings. Standard errors can be used to assess how precisely an estimate has been obtained, but the registry record does not state numerical primary-outcome estimates or standard errors. Without those values, the precision of the pleasurable-effects ratings cannot be assessed.

Why does the crossover structure matter?

In a crossover study, measurements from the same participant are often correlated. A comparison that accounts for this pairing can use within-participant information, while treating all measurements as independent may misrepresent uncertainty. This is a general statistical consideration, not a claim about the analysis used in this trial. The registry does not report the model used to account for repeated observations or whether it included period or sequence terms.

Incomplete participation can also affect a crossover analysis. The registry says four participants did not complete all five test sessions and that completed sessions were analyzed. It does not explain whether the analysis used every available session, required a specific set of sessions, or handled incomplete observations through another method. The resulting analysis population and the assumptions about missing observations are not reported in the registry record.

How should an estimate and its uncertainty be read?

A confidence interval, when reported, gives a range of values compatible with the data under the statistical procedure and its assumptions. It communicates uncertainty around an estimate, rather than guaranteeing that the true value lies in that particular interval. A p value, when reported, summarizes how incompatible the data are with a specified null hypothesis under a model; it does not measure the size or practical importance of an effect. Neither a confidence interval nor a p value for the primary endpoint is reported in this registry record.

For a dose-response question, analysis would need to represent how the outcome changes across dose conditions and account for the repeated observations where appropriate. A threshold question would require a defined rule for identifying the minimum dose at which self-administration exceeds placebo. These are general analytic requirements; the registry summary names these objectives but does not provide operational definitions or the statistical models used to address them. The posted primary endpoint is a pleasurable-effects rating, and its numerical results are not stated.

What does the planning illustration tell readers?

The registry’s planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation. The illustration is framed around detecting a stated fraction of an observed effect. Such a planning exercise is not observed power and is not a retrospective measure of how likely the completed study was to detect a result. Sample-size calculations are conditional on their assumptions and target effect; they do not replace reporting the observed estimate and its uncertainty.

The registry record does not state the numerical planning results, the effect estimate on which an illustration would depend, or the trial’s own sample-size justification. The summary’s earlier proposed enrollment and completer targets are not the same as the recorded enrollment of 34. The relationship between those planning figures and the completed study is not explained in the registry record. No conclusion about whether the final study met a statistical power target can be drawn from the available information.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures and describes several broader study aims, including threshold dose, dose-response slope, nicotine intake, nicotine clearance and self-reported drug effects. Examining multiple outcomes or comparisons can raise multiplicity concerns: when many hypotheses are tested, the chance of at least one apparently unusual result can increase. This is a general statistical issue, not evidence that a particular adjustment was used or needed in the trial.

The registry records zero analyses and does not report a statistical analysis plan, a hierarchy of outcomes, a multiplicity adjustment, or how the primary outcome was distinguished analytically from other measures. No inferential primary-outcome result is reported. It is therefore not possible to determine from the record which comparisons were tested or how their interpretation was intended to account for multiple testing.

The primary population note says that 34 participants were randomized, four did not complete all five test sessions, and completed sessions were analyzed. This is useful information about incomplete participation, but it does not specify the analysis population for each endpoint or the method used to handle missing sessions. The record does not say whether all randomized participants were included in any particular analysis, whether partially observed participants contributed, or what assumptions were made about unobserved outcomes.

The sample-size illustration is described using a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation. These are planning assumptions, not a reported multiplicity strategy, missing-data procedure, or analysis plan. The registry record does not report interim analyses or explain how the recorded sample size relates to the earlier proposed enrollment and completer targets. These omissions limit assessment of the intended inferential framework.

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 0% reporting threshold.

The registry lists serious adverse events, other adverse events and deaths separately for saline and each nicotine dose condition. For each listed condition, the recorded count is zero for serious adverse events, zero for other adverse events and zero deaths. The number at risk is reported as 34 for saline, 31 for nicotine 0.013, 32 for nicotine 0.025, 33 for nicotine 0.05, 31 for nicotine 0.1 and 33 for nicotine 0.2.

These entries should be read as the events recorded for the listed conditions and risk counts. The condition-specific numbers at risk differ, and a crossover design means those entries should not be added to infer a total number of participants. The registry does not describe the safety follow-up period, event-collection procedures, or how the risk counts were defined for each condition.

Zero recorded events do not establish that an event is impossible or that no unrecorded event occurred. They also do not quantify risk outside the study. The registry lists no serious adverse-event terms. These safety entries are a report of the recorded counts, not a substitute for primary-outcome results or a complete characterization of safety.

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

The record describes a randomized, double-blind crossover study in young adult light smokers and identifies a primary rating of pleasurable drug effects. It also outlines broader questions about nicotine self-administration across dose conditions. The study’s design and outcome descriptions clarify what investigators sought to examine, but the registry does not provide numerical primary-outcome results.

That absence matters for statistical interpretation. Without the reported least-squares means and standard errors, readers cannot judge the magnitude or precision of the pleasurable-effects ratings. Without a reported contrast or its uncertainty, readers cannot determine how the ratings differed across conditions from the registry record. The record also does not give numerical results for threshold dose or dose-response slope, so those broader questions cannot be answered from the posted information.

The absence of a numerical result is not evidence that there was no effect, nor is it evidence that there was an effect. It means the registry record does not permit a quantitative assessment. Likewise, the zero event counts describe the safety entries reported for the listed conditions; they do not establish that risk is absent in other settings or populations.

The registry’s sample-size assumptions are planning illustrations rather than observed power. They cannot fill the gap left by missing outcome estimates, and they do not establish how precisely the study measured the primary outcome. For readers, the appropriate distinction is between what is documented—the design, scale, incomplete sessions and recorded event counts—and what remains unreported, including numerical outcome results and key analysis details.

Accordingly, the record supports a careful account of the trial’s stated questions and reporting limits, but not a conclusion about the size, direction or statistical uncertainty of the primary outcome. It also does not provide enough information to assess the statistical handling of the crossover structure, missing sessions or multiple outcomes.

13. Why This Trial Matters Statistically

This trial raises a useful statistical distinction between a subjective drug-effect rating and a behavioral measure of reinforcement. The primary endpoint is a rating of pleasurable effects on a bounded scale, while the broader study summary emphasizes participants’ choices between nicotine and saline and the dose at which nicotine is self-administered more than placebo. These measures address related but non-identical questions. Keeping the endpoint and the broader objectives separate is essential when interpreting a study.

The crossover design also makes the dependence among observations important. When participants experience multiple conditions, analysis should reflect the repeated-measures structure rather than automatically treating every observation as independent. The registry identifies the design but does not report the statistical model, so readers cannot assess how that structure was handled.

The record further illustrates why outcome reporting needs both estimates and measures of uncertainty. Naming a scale and summary statistic does not tell readers the magnitude or precision of a finding. The primary outcome’s scale is described, but its numerical estimates and uncertainty are not reported in the registry record. This limits the statistical questions that can be answered, regardless of the study’s stated aims.

Finally, the record notes incomplete test sessions and lists condition-specific safety counts. Those details are important, but they do not by themselves explain the analysis population, missing-data assumptions or safety follow-up. The study is statistically informative as an example of how design, endpoint definition and transparent results reporting jointly shape interpretation.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main limitation for interpreting the posted results is that the registry does not report numerical findings for the primary pleasurable-effects endpoint. The least-squares means, standard errors, contrasts, confidence intervals and p values are not stated. Numerical findings for the broader self-administration objectives are also not reported in the registry record, so their magnitude and uncertainty cannot be assessed.

Important analytic details are absent. The record identifies a crossover design but does not report the condition sequence, statistical model, adjustment factors, treatment of within-participant correlation, or assessment of period or carryover effects. It also does not describe the method used to handle incomplete sessions. The note that four participants did not complete all five sessions does not establish how many observations contributed to each outcome analysis.

The population description is broad. The study summary refers to young adult male and female non-dependent light and intermittent smokers, but specific eligibility criteria and participant characteristics are not reported in the registry record. The record also gives no numerical outcome results with which to assess whether the enrolled participants’ ratings or behavior varied across the listed doses.

The registry’s enrollment is 34, while the study summary describes earlier proposed enrollment and completer targets. The record does not explain the relationship between those proposed targets and the completed study. It does not report the trial’s sample-size justification, a statistical analysis plan, multiplicity handling, or interim analyses. These omissions restrict assessment of the planned inferential framework and the generalizability of any conclusions.

Finally, the safety entries list zero recorded events in each condition, but the record does not describe event ascertainment or follow-up. Those counts should therefore be interpreted narrowly as the reported entries, not as a comprehensive measure of safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Nicotine Reinforcement and Aversion in Young Adult Light Smokers — NCT01495819.
• Registry record last updated 2021-08-31; status last verified 2021-08.
• Results first posted 2021-08-31.
• 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

NCT01495819 is recorded as a completed, randomized, double-blind crossover study at Yale University, with enrollment of 34. The registry describes nicotine and saline conditions and a study population of young adult light and intermittent smokers. The primary outcome is the DEQ pleasurable-effects rating, measured up to 10 minutes on a scale from zero to 100 millimeters and summarized as a least-squares mean with standard error.

The summary also describes broader questions about nicotine self-administration across five dose levels. Four participants did not complete all five test sessions, and completed sessions were analyzed according to the primary-outcome population note. Numerical primary-outcome results and details of the statistical model are not reported in the registry record. The listed safety counts are zero serious adverse events, zero other adverse events and zero deaths for saline and each nicotine condition.