Oxytocin Pathways and the Health Effects of Human-Animal Interaction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Oxytocin Pathways and the Health Effects of Human-Animal Interaction (NCT03852264), a non-randomized na study. The primary outcome is Salivary Oxytocin, Area Under the Curve.

2. Clinical Question

3. Trial Design

This was a completed, non-randomized crossover study sponsored by the University of Arizona. The record lists an enrollment of 55, a single masking designation, and a crossover model. It does not identify who was masked; that information is not reported in the registry record. The study began on 2019-03-08 and had a primary completion date of 2022-01-10.

The behavioral conditions were interaction with a participant’s pet dog, interaction with an unfamiliar dog, and a nonsocial toys condition. The described sequences place the toys visit between the two dog visits. One sequence begins with the participant’s pet dog and ends with an unfamiliar dog; the other begins with an unfamiliar dog and ends with the participant’s pet dog. Each visit description specifies 25 minutes in its condition. The record does not state how participants were assigned to the sequences, or whether other sequences were possible; those details are not reported in the registry record.

A crossover design means that participants can experience more than one condition, so comparisons may draw on observations from the same people rather than on entirely separate groups. This can be useful when outcomes vary substantially between people. It also makes the order and timing of conditions important: responses may differ depending on which condition came first, or whether an earlier condition influences a later one. The registry identifies the design as crossover but does not describe the statistical handling of sequence, period, or carryover effects. Those methods are not reported in the registry record.

The record lists four outcome measures and nine analyses. It identifies salivary cortisol area under the curve and urinary vasopressin area under the curve as secondary outcomes. The other outcome measures and the mapping of analyses to outcomes or comparisons are not reported in the registry record. The study status is completed, but completion alone does not establish what the results were or how completely results were reported.

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: None / not applicable

First Research Visit

Second Research Visit

Third Research Visit

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All study participants for whom saliva samples were available for analysis

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 Salivary Oxytocin, Area Under the Curve, measured over baseline, 15 minutes.

The primary endpoint is salivary oxytocin area under the curve with respect to the initial value (AUCi). The registry describes it as a change from baseline, with measurements at baseline and 15 minutes, and gives the unit as pg/mL x minutes. The endpoint is specified as a mean of a continuous measure, with standard error as its dispersion measure. Its analysis population is participants for whom saliva samples were available for analysis.

In general, an area-under-the-curve measure combines information across measurements over time into a single summary. AUCi is defined relative to the initial value, so it describes the pattern of change in relation to baseline rather than simply the total level across the measurement period. This can be useful when the research question concerns a response over time and when a single summary is desired for comparison across conditions. The interpretation depends on the measurement schedule, the calculation procedure, and the meaning assigned to the outcome.

The registry does not report the actual endpoint values, the standard errors, or comparisons between conditions; these are not reported in the registry record. It also does not give details about saliva collection, assay procedures, or how measurements with missing time points were handled. Those details are not reported in the registry record. Thus the endpoint definition is available, but its observed size and precision cannot be assessed from the listed information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a continuous primary outcome summarized as a mean, with standard error as the dispersion measure. A mean is a measure of the central level of a set of observations. A standard error describes the statistical uncertainty in an estimated mean due to sampling variability; it is not the same thing as the spread of individual participants’ measurements. In general, a confidence interval combines an estimate with an uncertainty measure to show a range of values reasonably compatible with the data under the analysis assumptions. No numerical mean, standard error, or confidence interval for the primary outcome is reported in the registry record.

What does the area-under-the-curve endpoint represent?

The primary endpoint is salivary oxytocin AUCi, with baseline and 15-minute measurement times and a unit of pg/mL x minutes. In general, area under the curve summarizes measurements across time, while the “with respect to the initial value” specification makes the summary relative to the starting measurement. It can therefore represent an overall response pattern rather than a single measurement at one time point. The registry describes the endpoint as change from baseline. The detailed calculation procedure, handling of incomplete measurement series, and assay methods are not reported in the registry record.

How does a crossover design affect analysis?

In general, a crossover design exposes participants to more than one condition. This can allow each participant to serve as their own reference, reducing the influence of stable differences between people in a comparison. But observations from one participant are related, so an analysis should account for that dependence rather than treating every observation as independent. Condition order can also matter. A response during a later visit might be influenced by the earlier visit, and responses may vary by period or sequence. The record identifies a crossover model and gives two sequences, but the particular statistical model and its handling of within-person correlation, period, sequence, or carryover are not reported in the registry record.

The non-randomized allocation designation is also important. In general, random allocation is intended to make comparison groups similar, on average, with respect to both measured and unmeasured factors. Without random allocation, differences in sequence or condition exposure may be related to participant characteristics or other factors. The record does not describe how sequence allocation occurred, whether baseline characteristics were compared, or what adjustments were made. These details are not reported in the registry record, so the extent to which the analysis addresses potential confounding cannot be assessed.

What does the standard error tell a reader?

In general, a standard error concerns the precision of an estimated quantity, not the range of individual participant responses. Smaller uncertainty around an estimate would usually indicate greater precision under the model used, while wider uncertainty would indicate less precision. A confidence interval is often easier to interpret because it expresses uncertainty on the same scale as the outcome. The record lists standard error as the dispersion measure, but it does not provide the actual estimate or its standard error. The precision of the primary result is therefore not reported in the registry record.

How should the planning illustration be understood?

The record describes a sample-size planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration considers detecting a stated fraction of the observed effect. Such calculations are planning scenarios, not evidence that a study had a particular probability of finding a result after it was conducted. They do not establish the power of the completed study. The numeric observed effect and the resulting participant counts are not reported in the registry record. The illustration’s assumptions also describe equal allocation between two arms, whereas the study description involves three conditions and a non-randomized crossover structure; the registry does not explain how the illustration relates to the actual design.

Why do repeated measurements and extra analyses matter?

When an analysis includes repeated measurements from the same participant, the observations generally share information and are statistically dependent. In general, a model that recognizes that dependence can give more appropriate uncertainty estimates than one that assumes independence. Likewise, when the variability in data is greater than a model expects, that is called over-dispersion. In general, ignoring over-dispersion can make uncertainty appear too small and can lead to overly confident conclusions. The record does not state whether over-dispersion was assessed or how repeated observations were modeled; those methods are not reported in the registry record.

The registry lists four outcome measures and nine analyses. In general, conducting many statistical tests creates a multiplicity issue: even when no underlying condition differences exist, the chance of at least one small p-value can increase as the number of tests grows. Methods such as prespecifying a primary analysis or adjusting inference can address particular multiplicity concerns, but no such approach should be assumed. A multiplicity plan, analysis hierarchy, and exact list of comparisons are not reported in the registry record. The outcome and analysis counts alone do not indicate which results, if any, were statistically persuasive.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Pet Dog Interaction", "Unfamiliar Dog Interaction", "Toys Interaction")
n   <- c(55, 53, 55)
m   <- c(-3.03, -3.83, -5.57)
sp  <- c(1.59, 1.67, 1.73)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Pet Dog Interaction  55  -3.030  11.792  -6.218  0.158
CARM  Unfamiliar Dog Interaction  53  -3.830  12.158  -7.181  -0.479
CARM  Toys Interaction  55  -5.570  12.830  -9.038  -2.102

11. Multiplicity, Missing Data and Analysis Populations

The record lists four outcome measures and nine analyses, but does not report a multiplicity strategy. It does not identify a hierarchy of outcomes, state whether the primary endpoint was the only confirmatory analysis, or describe any adjustment of significance levels or confidence intervals across outcomes and comparisons. These details are not reported in the registry record. In general, testing multiple hypotheses can increase the chance of finding at least one result that appears unusual by chance, so the analysis plan matters when interpreting several results together. The count of analyses alone does not establish that any particular correction was needed or used.

The primary outcome population is described as all study participants for whom saliva samples were available for analysis. The number of participants with available samples, the number analyzed for each outcome, and the reasons samples were unavailable are not reported in the registry record. The record does not say whether missing measurements were excluded, imputed, or addressed by another method. Those details are not reported in the registry record. Without them, it is not possible to assess whether the analyzed participants represent the enrolled participants or whether missing data could affect the estimates.

The record does not report a full analysis population definition for the secondary outcomes, or whether all enrolled participants were included in every analysis. That information is not reported in the registry record. Nor does it describe how the crossover design, repeated measurements, or sequence assignment were handled in the analyses. These omissions limit assessment of both the statistical comparisons and the extent to which results across outcomes can be interpreted as a coherent set.

12. 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 safety counts for Pet Dog Interaction, Unfamiliar Dog Interaction, and Toys Interaction. For each listed group, the serious adverse event count is 0 and the other adverse event count is 0. The death count is also 0 for each group. The record lists 55 participants at risk in the Pet Dog Interaction group, 54 in the Unfamiliar Dog Interaction group, and 55 in the Toys Interaction group for both serious and other adverse events.

These entries describe the counts recorded for the groups; they do not provide event narratives or information about how adverse events were defined, collected, or attributed. The registry does not report those details. Because the study is described as a crossover, the group counts should not automatically be read as independent sets of participants. The record does not explain how the safety denominators relate to participants’ exposure across conditions. That information is not reported in the registry record.

Zero recorded events in these fields should be read narrowly as the registry counts, not as proof that no event of any kind occurred during the study. The period of safety surveillance and completeness of adverse-event reporting are not reported in the registry record.

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

The record makes it possible to identify the study’s focus and design: a non-randomized crossover investigation of human-animal interaction, with dog interaction and a toys condition, and salivary oxytocin AUCi as the primary endpoint. It also identifies cortisol and vasopressin area under the curve as secondary outcomes. These registry entries clarify what the investigators set out to measure, but they do not establish the direction or size of any observed response.

The numerical primary outcome results are not reported in the registry record. The record does not give condition-specific means, comparison estimates, standard errors, confidence intervals, or p-values. Therefore, it is not possible to state from this information whether measurements differed by condition, how large any difference might have been, or how precisely it was estimated. No conclusion about the effects of the interactions can be drawn from the endpoint definition or study completion status alone.

The non-randomized allocation and crossover structure also shape what an eventual comparison would mean. A within-participant comparison can account for stable differences between individuals in some circumstances, but order, period, carryover, and allocation processes may still matter. The registry does not report the model or procedures used to address these issues. That information is not reported in the registry record, so the strength of causal interpretation cannot be assessed.

The safety fields record zero serious adverse events, zero other adverse events, and zero deaths in each listed group. Those counts are descriptive registry entries; they do not provide detailed information about collection or follow-up. More broadly, the absence of numerical efficacy results and analysis details means the record supports a careful account of the research question and planned measurements, not a determination of what the data show.

14. Why This Trial Matters Statistically

This study raises statistical questions that are common in behavioral and clinical research. Its crossover structure allows the same participants to experience multiple conditions, which can make within-person contrasts relevant. Those comparisons require attention to the dependence among repeated measurements, as well as to visit sequence and potential carryover. The record identifies the design and two sequences, but does not report the model used to account for these features.

The non-randomized allocation designation makes the basis for comparison especially important. A comparison of conditions can be influenced by differences associated with sequence assignment or participant characteristics, in addition to the conditions themselves. Knowing how assignment occurred and how the analysis handled possible imbalances would help readers assess interpretation. Those details are not reported in the registry record.

The endpoint also illustrates the distinction between defining a measure and reporting its result. AUCi is intended to summarize change over time relative to an initial value, and its mean and standard error describe a continuous outcome and its estimated precision. Without the numeric estimates and uncertainty, readers cannot judge the size or precision of the measured response. The outcome definition alone does not answer the study question.

Finally, the record lists multiple outcomes and analyses. This makes transparency about the analysis plan and multiplicity relevant, especially when interpreting a set of comparisons. The registry does not report that plan. The case therefore underscores why design details, analysis methods, missing-data information, and numerical results are all needed for a statistical reading of a completed study.

15. 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 available record does not report numerical results for the primary or secondary outcomes. Primary outcome estimates, uncertainty measures, comparison results, and p-values are not reported in the registry record. This prevents assessment of the observed effect’s direction, magnitude, and precision.

Important design and analysis details are also absent. Although the study is identified as non-randomized and crossover, the procedure for assigning participants to sequences, the identity of the masked party, and the handling of period, sequence, and carryover effects are not reported in the registry record. The record does not describe the statistical model for repeated measurements or whether any adjustments were made for participant characteristics.

The primary analysis population requires saliva samples to be available, but the number of participants with available samples and the extent or reasons for missing data are not reported in the registry record. The record also does not describe missing-data handling or clarify the analysis populations for every outcome. This limits evaluation of representativeness and potential bias from missing measurements.

The registry lists four outcome measures and nine analyses but does not report the full analysis plan, the comparisons conducted, or any approach to multiplicity. The detailed endpoint calculation and laboratory procedures are not reported in the registry record. Finally, the zero safety counts are not accompanied by information about event definitions, ascertainment, or surveillance. These limitations leave readers able to describe the study structure, but unable to evaluate the complete statistical evidence or the robustness of its conclusions.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Oxytocin Pathways and the Health Effects of Human-Animal Interaction — NCT03852264.
• Registry record last updated 2024-11-12; status last verified 2024-03.
• Results first posted 2024-11-12.
• 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.

19. Record Summary

NCT03852264 is a completed, non-randomized crossover study sponsored by the University of Arizona. It enrolled 55 participants and investigated interactions with a participant’s pet dog, an unfamiliar dog, and a nonsocial toys condition. The registry describes two sequences, with the toys condition between the dog interactions, and specifies 25 minutes for each described visit condition.

The primary endpoint was salivary oxytocin AUCi, described as change from baseline and measured at baseline and 15 minutes. Salivary cortisol and urinary vasopressin area under the curve were secondary outcomes. Numerical outcome results and detailed analysis methods are not reported in the registry record. The safety entries list zero serious adverse events, zero other adverse events, and zero deaths in each of the three groups.