Effects of Stress-reducing Aromatherapy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effects of Stress-reducing Aromatherapy (NCT01307748), a randomized phase 2, phase 3 study. The primary outcome is Percent of Baseline Level of Salivary Cortisol.

2. Clinical Question

The clinical question is therefore about physiological response across the study’s assessment periods, rather than a single reported estimate of the effect of lavender versus a specified comparator. The registered description also indicates interest in expectancy effects and in how aromatherapy works. However, the record does not provide enough detail to determine how expectancy was measured or incorporated into the analysis.

The listed secondary outcomes are electroencephalography frontal asymmetry and percent change from baseline in Digit Span Backward Task score. These outcomes concern different measurements from salivary cortisol. The registry lists three outcome measures and two analyses, but does not report a complete mapping between outcomes, analyses, and comparisons. No clinical conclusion about the aroma can be drawn from the endpoint title alone.

3. Trial Design

This was a randomized, single-masked, parallel-design study listed as Phase 2 and Phase 3. The registry record gives enrollment as 92 and identifies Oregon Health and Science University as the sponsor. The study status is completed. Its start is recorded as 2010-12 and primary completion as 2012-12.

The parallel design means the registered arms represent separate groups rather than a crossover sequence in which each participant receives each aroma. Random allocation indicates that assignment was intended to be randomized. The registry record does not report the randomization sequence method, allocation concealment procedures, or whether assignment was balanced across arms.

Three arms are described: stress-reducing aroma, labeled lavender; detectable placebo aroma, labeled coconut; and undetectable placebo aroma, labeled water. The record classifies masking as single but does not identify who was masked. It therefore cannot establish from the registry entry whether participants, investigators, outcome assessors, or another group were unaware of assignment. Nor does it report whether masking was tested or maintained.

The intervention is classified as “other” in the intervention listing. The arm description characterizes lavender as an aroma with reported stress-reducing effects, but the registry record does not provide a detailed protocol for exposure. It does not report the aroma concentration, administration procedure, exposure duration, or whether the stress task was standardized in a particular way.

The primary outcome assessment is described at baseline, during the stress battery after aroma exposure, and after completion of the stress battery. This repeated timing is important to the outcome’s interpretation: a value at one assessment period is not interchangeable with a value at another. The record does not state the exact analysis used to account for measurements over time, or how the three arms were compared. It also does not report a protocol rationale for the enrollment target or a sample-size justification.

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 Percent of Baseline Level of Salivary Cortisol, measured over assessed at baseline (60 min prior to aroma exposure and stress), stress battery (30 min after aroma exposure and during stress), post-stress (60 min after completing stress battery).

The primary endpoint is percent of baseline level of salivary cortisol. The registry describes the measure as a mean with standard error and gives its unit as percentage of baseline cortisol level. It also states that values greater than baseline indicate increased stress.

Salivary cortisol is used in this study as a physiological measure associated with the stress battery. Expressing the measurement relative to baseline makes the assessment periods interpretable in relation to each participant’s baseline level, as described by the registry. The endpoint was assessed at baseline, 60 minutes prior to aroma exposure and stress; during the stress battery, 30 minutes after aroma exposure and during stress; and post-stress, 60 minutes after completing the stress battery.

These time points represent different stages of the study procedure. A baseline assessment gives a reference, while the stress-battery and post-stress assessments concern response during and after the task. General statistical point: repeated measurements can describe how an outcome changes across time, but comparisons must specify which time point or pattern of change is being evaluated.

The registry record does not report the actual cortisol means, standard errors, confidence intervals, or a single contrast among the arms. It also does not specify whether the primary analysis compared each aroma with both placebo aromas, tested change over time, or used another contrast. Because the primary outcome includes several time points and is not reduced to one comparison in the registry record, the endpoint definition alone does not show the direction or precision of any treatment effect.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomization, masking, outcome timing, and the choice of comparison all affect how trial results should be interpreted. The registry record gives some design labels but leaves important analysis details unreported. The following statistical explanations are general; they do not imply that a particular method was used in this trial.

What does randomization contribute?

Random allocation is intended to make treatment groups comparable, on average, with respect to both measured and unmeasured characteristics before the intervention. This supports a causal interpretation of a between-group comparison when the trial is conducted and analyzed appropriately. Randomization does not guarantee that groups will be identical, especially in a study of limited size, and it does not eliminate the need to describe the analysis population, adherence, or missing outcome data.

The registry identifies the allocation as randomized, but the sequence-generation method and allocation-concealment procedures are not reported in the registry record. Those details matter because a random sequence and concealment before assignment address different risks of bias. The record also does not explain whether participants were analyzed according to their assigned arms or according to the aroma actually received.

Why does the parallel design matter?

In a parallel trial, each participant is assigned to an arm and the groups are compared. This differs from a crossover design, where participants receive more than one intervention in sequence. The registry identifies this study as parallel, but does not report further details about adherence, exposure, or whether participants changed or stopped their assigned aroma.

There are three registered arms: lavender, coconut, and water. A statistical comparison must define which arms are being contrasted. For example, lavender could be compared separately with each placebo arm, but the registry record does not specify the primary contrast or report the corresponding estimates. The two placebo aromas also have different descriptions: one is detectable and the other undetectable. Their labels alone do not establish that they functioned identically as controls.

How should the repeated cortisol measurements be understood?

The primary outcome is assessed at baseline, during the stress battery, and post-stress. These measurements represent different stages of the procedure. A comparison at one time point answers a different question from a comparison of change from baseline or a comparison of trajectories over time. General statistical point: repeated measurements from the same participant are related, so an analysis should account for that within-participant relationship rather than treating all measurements as independent observations.

The registry record does not describe the statistical model used for the repeated cortisol measurements. It does not state whether the analysis used a repeated-measures model, compared selected time points, or evaluated a treatment-by-time pattern. It also does not report how baseline cortisol was incorporated into the analysis. Without those details, the intended estimand—the particular effect the analysis aims to estimate—cannot be identified from the registry entry.

What do mean and standard error communicate?

The primary measure is characterized as a mean with standard error. A mean describes the average outcome in a group under the relevant definition. A standard error describes the uncertainty in an estimated mean, rather than the spread of individual participants’ measurements. General statistical point: a confidence interval combines an estimate with an uncertainty range and is often more informative than a significance test alone because it shows which effect sizes remain compatible with the data and analysis assumptions.

The registry record does not report the cortisol means, standard errors, or confidence intervals. Nor does it provide an estimated contrast between groups. The outcome’s statistical summary type therefore describes what was planned or recorded as the measure, but does not reveal the study’s numerical findings.

How should multiple outcomes and comparisons be considered?

The record lists a primary outcome with several time points and two secondary outcomes. It also states that three outcome measures and two analyses are listed. When a study examines multiple outcomes, time points, or arm comparisons, the analysis plan determines which tests are confirmatory and how the risk of false-positive findings is handled. General statistical point: multiplicity refers to the interpretive challenge created by conducting multiple statistical tests; methods such as prespecifying a primary contrast or adjusting inference can address it, but no such method should be assumed without documentation.

The registry does not report a multiplicity strategy or identify one primary comparison across the time points and arms. It also does not explain which outcome measures correspond to the reported analyses. Thus, the available record does not support interpreting any one unreported comparison as the definitive result.

What can planning calculations tell readers?

General statistical point: a sample-size calculation is a planning exercise based on assumptions about the effect to detect, variability, allocation, and statistical testing. It is not an observed result. A calculation based on an effect seen in the same trial is particularly dependent on that estimate and should not be described as observed power. The registry’s planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect expressed as a fraction of the observed effect. The registry record does not report the trial’s own sample-size justification, and the planning assumptions do not establish that the trial was designed around a particular primary contrast.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome is reported across baseline, stress-battery, and post-stress assessments, but the registry record does not reduce these time points to one comparison. The record also lists two secondary outcomes and three outcome measures, alongside two analyses, without explaining the relationship among them. A multiplicity plan—such as which comparison was primary or how multiple tests were handled—is not reported in the registry record.

Missing-data methods are not reported in the registry record. The entry does not say whether outcome data were missing, how any missing measurements were handled, or whether sensitivity analyses were planned. It also does not describe the analysis population, including whether participants were analyzed as randomized or under another rule. Enrollment is listed as 92, but the registry does not provide a primary-outcome analysis denominator or arm-specific cortisol denominators.

These omissions limit interpretation because decisions about which measurements and participants enter an analysis can affect estimates and their uncertainty. General statistical point: when repeated measurements are missing, the amount and pattern of missingness, along with the assumptions of the chosen method, matter to the validity of the estimate. The registry record does not provide enough information to assess those issues for this study.

The planned sample-size assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They do not supply a trial-specific rationale, a primary contrast, or a missing-data strategy. No particular interim analysis or statistical analysis plan is reported in the registry record.

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.

Most frequent non-serious adverse event terms

The registry lists serious adverse events, other adverse events, and deaths by arm. Serious adverse events are reported as 0 in each arm, and deaths are reported as 0 in each arm. The risk denominators for serious and other adverse events are 31 for lavender, 31 for coconut, and 30 for water. The other adverse-event counts are 1 for lavender, 0 for coconut, and 0 for water.

These are descriptive counts from the registry record. They do not establish that the arms had equivalent safety, nor do they show that an event was caused by an aroma. The record does not give descriptions of the other adverse event, its severity, timing, or relationship to the intervention. It also does not report a statistical comparison of adverse events.

General statistical point: zero recorded events does not prove that an event cannot occur; it means no event was reported in the corresponding registry count. Interpretation also depends on how events were defined, collected, and followed. Those procedures are not reported in the registry record. The safety figures should therefore be read as the reported counts and denominators, not as a complete assessment of risk.

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

The registry record establishes that this was a randomized, single-masked, parallel study of stress-reducing aroma in older adults, with lavender and two placebo aroma arms. It identifies salivary cortisol as the primary outcome and describes assessments at baseline, during a stress battery, and after the stress battery. It also lists frontal asymmetry and Digit Span Backward Task performance as secondary outcomes.

Those design details clarify the question the study addressed, but they do not provide the numerical outcome results. The record does not report the group means, between-arm estimates, confidence intervals, or significance tests for cortisol. It also does not report numerical findings for the secondary outcomes. The primary outcome is not reduced to one comparison across its multiple time points. As a result, the direction and precision of any treatment effect cannot be determined from the registry record.

The definitions should not be mistaken for findings. In particular, the registry’s note that values greater than baseline indicate increased stress explains the outcome’s scale; it does not show that values rose in any arm. Likewise, the description of lavender as an aroma with reported stress-reducing effects is an arm description, not a result from this trial.

The safety record reports no serious adverse events or deaths in the listed arms, and reports one other adverse event for lavender and none for either placebo aroma. These counts are not a formal comparison and are not accompanied by event descriptions. They do not, by themselves, establish either benefit or harm.

General statistical point: a trial’s design can make an effect estimate more interpretable, but conclusions depend on the observed results and the analysis used to obtain them. Since those results and key analysis details are not reported in the registry record, no conclusion about the efficacy of aromatherapy or the size of any physiological response follows from this record alone.

13. Why This Trial Matters Statistically

This trial is statistically interesting because it places a physiological measure within a defined sequence: baseline, a stress battery after aroma exposure, and a post-stress assessment. That structure raises a central analysis question: whether the relevant comparison is a value at a particular time, change from baseline, or a pattern across the assessment periods. Those are distinct statistical questions, and the registry record does not identify one reduced primary comparison.

The three-arm design also makes the comparator important. Lavender is compared with a detectable placebo aroma, coconut, and an undetectable placebo aroma, water. These controls are labeled differently in relation to detectability, but the record does not explain how expectancy was measured or how each comparison was intended to separate physiological response from expectation. The study title and purpose refer to physiological and expectancy effects; the registry description alone does not show how those effects were distinguished analytically.

The listed secondary outcomes further illustrate that trials can measure more than one dimension of response. Frontal asymmetry and cognitive performance are not the same construct as salivary cortisol, and the registry does not report their results or a plan for interpreting them alongside the primary outcome. This makes prespecification and transparent reporting of comparisons important to a reader’s assessment.

The record also shows why design labels are not a substitute for results. Randomization and masking are useful design features, but the record does not identify who was masked or provide the outcome estimates needed to judge magnitude and precision. The study can therefore prompt useful questions about repeated measures, control selection, and multiplicity, while the registry entry remains insufficient for a quantitative efficacy conclusion.

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.

A key limitation of the available registry record is that it does not report the primary-outcome values or a single comparison across the listed assessment periods. The cortisol measure is defined, but its group means, standard errors, confidence intervals, and between-arm estimates are not reported. The same is true of numerical results for the listed secondary outcomes.

The record does not specify the primary contrast among the three arms. It also does not explain how the multiple time points were handled statistically, whether baseline values were adjusted for, or how repeated measurements were modeled. The analysis plan, multiplicity approach, and relationship between the listed outcome measures and analyses are not reported in the registry record.

Several design details are also absent. The record labels the study single-masked but does not identify who was masked. It does not report the randomization method, allocation concealment, eligibility criteria, detailed aroma exposure procedure, adherence, or whether masking was assessed. These omissions make it difficult to evaluate implementation and potential sources of bias from the registry information alone.

Missing-data handling and the analysis population are not reported in the registry record. The entry provides enrollment and safety denominators, but does not give arm-specific denominators for the primary outcome or state how incomplete assessments were treated. A trial-specific sample-size justification is also not reported. The listed planning assumptions are not a substitute for the study’s own design rationale or for observed treatment-effect estimates.

Finally, the safety entry gives counts without descriptions of other adverse events or a formal comparison. These limitations concern what the registry record reports; they do not establish what may or may not have been described elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effects of Stress-reducing Aromatherapy — NCT01307748.
• Registry record last updated 2019-08-19; status last verified 2019-07.
• Results first posted 2019-08-19.
• 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 identifies NCT01307748, “Effects of Stress-reducing Aromatherapy,” with the official title “Physiologic and Expectancy Effects of Stress-reducing Aroma in Older Adults.” Oregon Health and Science University is listed as sponsor. The study is recorded as randomized, single-masked, parallel, and Phase 2 and Phase 3, with enrollment of 92 and completed status.

The arms are stress-reducing aroma, identified as lavender; detectable placebo aroma, identified as coconut; and undetectable placebo aroma, identified as water. The primary outcome is percent of baseline level of salivary cortisol, assessed at baseline, during the stress battery, and post-stress. Listed secondary outcomes are electroencephalography frontal asymmetry and percent change from baseline in Digit Span Backward Task score.

The registry record does not report a single primary comparison or numerical efficacy results. It reports no serious adverse events or deaths in the listed arms and one other adverse event for lavender, with none reported for either placebo aroma. Missing-data methods, analysis populations, and the detailed statistical plan are not reported in the registry record.