Mechanisms of Mindfulness-based Interventions: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Mechanisms of Mindfulness-based Interventions (NCT03571386), a registered phase not stated study. The primary outcome is Change in BOLD (Blood-oxygen-level-dependent) Mean Signal Change From Baseline to 12 Weeks in Response to Emotional (vs. Neutral) Word Stimuli.

2. Clinical Question

3. Trial Design

This is a completed study titled “Mechanisms of Mindfulness-based Interventions,” sponsored by Vanderbilt University Medical Center. The record lists an enrollment of 136 and identifies depression, anxiety, and stress as the conditions of interest. Its summary describes a mixed methods investigation of proposed neurobiological, physiological, psychosocial-behavioral, and cognitive mechanisms through which mindfulness-based interventions may relate to health outcomes.

The record describes two participant groups rather than a randomized, like-for-like treatment comparison. Participants with mild to moderate depression and/or anxiety symptoms who were receiving MBCT in a group setting as standard of care were recruited for one group. Participants with a history of reported stress who were receiving MBSR in a group setting as standard of care were recruited for the other. Allocation is not stated, and the registry record does not report a control group or a method for assigning participants to interventions.

The primary endpoint is a change in fMRI BOLD mean signal from baseline to 12 weeks, following MBCT, in response to emotional versus neutral word stimuli. The endpoint description says that only 16 participants in the mild to moderate depression and/or anxiety group participated in fMRI data collection. The High Stress group was not assessed using fMRI; the record attributes the smaller subgroup to financial constraints.

The study status is completed. The record lists five outcome measures, including two secondary outcomes concerning an ERP response to threat versus neutral face cues and response time on a dot-probe task. It lists no analyses. Protocol details such as a randomization procedure, blinding, and a statistical analysis plan 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Only 16 participants in Mild to moderate depression and/or anxiety participated in fMRI data collection. Participants in the "High Stress" Arm/Group were not assessed using fMRI and the subgroup was smaller given financial constraints.

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: mild to moderate anxiety cohort was same as mild to moderate depression

6. Primary Endpoint

The registry lists the primary outcome as Change in BOLD (Blood-oxygen-level-dependent) Mean Signal Change From Baseline to 12 Weeks in Response to Emotional (vs. Neutral) Word Stimuli, measured over Baseline to 12 weeks.

The primary endpoint is the change from baseline to 12 weeks in mean BOLD signal in response to emotional, compared with neutral, word stimuli. BOLD is short for blood-oxygen-level-dependent. The endpoint description specifies fMRI measurement after MBCT and extraction of signal from voxels within fronto-parietal and default mode areas at baseline and 12 weeks.

The emotional-versus-neutral contrast is intended to represent the difference in brain response to emotional words relative to neutral words, rather than response to emotional words alone. The endpoint description says that voxel-wise activity is reported using z-scores from peak voxels and that a mean score was calculated based on the z-score and an SD of 2. It explains a z-score as a measure of how many standard deviations a data point is from the mean of its signal distribution. The record further states that a higher reported mean indicates less likelihood that the observed activation is due to chance. The underlying statistical procedure for that interpretation is not reported in the registry record.

Brain imaging is used in this study to examine a proposed mechanism, not as a direct measure of depression, anxiety, or stress symptoms. The registry record gives the endpoint definition but does not report the numerical baseline-to-12-week change, its standard error, or an uncertainty interval. The available record therefore does not establish the size or precision of any observed endpoint change.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes a continuous primary measure summarized as a mean, with standard error listed as its dispersion measure. It does not provide a numerical mean, standard error, or analysis result. The paragraphs below explain general statistical concepts relevant to those terms; they do not identify methods that the investigators used unless the record explicitly says so.

What does a mean represent?

General: A mean is an average of measured values. For this endpoint, the stated measure is a mean BOLD signal change in response to the emotional-versus-neutral word contrast. A mean can summarize the center of a set of measurements, but it does not show how individual observations are distributed. The registry record does not report individual-level values or a numerical group mean.

What does the standard error describe?

General: The standard error describes the precision of an estimated mean. It is not the same as the standard deviation, which describes spread among individual observations. A smaller standard error generally indicates a more precisely estimated mean, while a larger standard error indicates greater uncertainty in that estimate. The record names standard error as the dispersion measure for the primary endpoint but does not report its value. The endpoint description also refers to an SD of 2 in connection with its mean score; it does not explain how that quantity relates to the listed standard error.

How would a confidence interval help?

General: A confidence interval gives a range of values compatible with an estimate under a stated statistical procedure. Its width conveys precision: a wider interval reflects more uncertainty than a narrower interval. A confidence interval would help readers judge whether a reported change is estimated precisely or remains compatible with a broad range of values. No confidence interval for the primary endpoint is reported in the registry record, and the missing estimate and standard error cannot be reconstructed from the endpoint description.

What does the imaging contrast mean?

The endpoint compares BOLD responses to emotional and neutral word stimuli. General: A contrast is a difference defined between two measured conditions. It focuses the analysis on the relative response between those conditions, rather than treating either condition in isolation. The record says that signal change is estimated from the emotional-word versus neutral-word contrast and extracted from voxels in fronto-parietal and default mode areas at baseline and 12 weeks. It does not give the voxel-level measurements, the procedure used to summarize voxels, or the statistical model used to estimate the change.

The record says that significant voxel-wise activity is reported using z-scores from peak voxels, and that a mean score was calculated based on the z-score and an SD of 2. General: A z-score expresses a value relative to a distribution in standard-deviation units. However, the registry record does not provide the values, the distributional assumptions, or the threshold and procedure used to determine significance. Its statement that a higher reported mean indicates activity less likely to be due to chance is part of the endpoint description; the inferential method behind that statement is not reported.

What can the sample-size assumptions tell readers?

The record describes planning illustrations based on the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says that the effect to detect is a stated fraction of the observed effect. These are assumptions for planning illustrations, not a report of the trial’s actual design justification or observed power. The numbers of participants per arm for those illustrations are not reported in the registry record. The record also does not report the observed effect estimate needed to interpret such illustrations. The planning assumptions do not establish that the study was randomized or that its two participant groups formed a valid direct comparison.

General: Sample-size calculations describe how many participants may be needed under specified assumptions to target a chosen power for a particular effect. They depend on assumptions about the outcome, variability, comparison, and analysis. Planning values should not be treated as evidence that an effect occurred, nor as a measure of the study’s power after data collection. In this record, the actual statistical plan and sample-size justification are not reported in the registry record.

Why does the small imaging subgroup matter?

The primary endpoint uses fMRI data from only 16 participants in the mild to moderate depression and/or anxiety group. General: Fewer observations usually mean less information for estimating a mean and can result in wider uncertainty, though the precision depends on the variability and analysis as well as the number of observations. No variability estimate or standard error is posted, so the actual precision cannot be quantified. The absence of fMRI data from the High Stress group also prevents an imaging comparison between the two groups.

Finally, the registry record lists zero analyses and does not report a test statistic, p-value, confidence interval, or model specification. The statistical concepts above help explain what those results would ordinarily convey, but they cannot substitute for the missing endpoint estimate and analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists five outcome measures, including the primary BOLD endpoint and two secondary outcomes. The secondary outcomes concern the amplitude of P1 event-related potentials in response to threat versus neutral face cues from pre- to post-MBCT, and response time to probes as a function of emotion and congruency in the dot-probe task. The other listed outcome measures are not identified in the record. No analyses are listed.

When a study assesses multiple outcomes or performs multiple statistical tests, the chance of at least one apparently unusual result can increase. General: A multiplicity strategy may specify which outcome is primary, how related tests are grouped, or whether statistical thresholds are adjusted. The registry record does not report whether any multiplicity strategy was planned or used. It also does not report which analyses, if any, were intended for the secondary outcomes.

Information about missing data and analysis populations is also limited. The record says that 16 participants in the mild to moderate depression and/or anxiety group participated in fMRI data collection and that the High Stress group was not assessed using fMRI. It does not report how many participants had complete measurements at both baseline and 12 weeks, how missing observations were handled, or whether any participants were excluded from an analysis. It does not describe an intention-to-treat population, a per-protocol population, or other analysis-population definitions.

These omissions matter because the number and pattern of available observations can affect the estimate and its uncertainty. Without analysis details, it is not possible to determine how the endpoint was calculated for participants with incomplete data, or whether the posted estimate represents all participants who began the intervention or only those with usable measurements. No such estimate is posted 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.

The registry record lists serious adverse events and other adverse events separately for each group. For Mild to Moderate Depression and/or Anxiety, 69 participants were at risk for serious adverse events and 69 were at risk for other adverse events; the recorded counts affected were 0 for serious events and 0 for other events. For High Stress, 67 participants were at risk for each category; the recorded counts affected were 0 for serious events and 0 for other events. The recorded number of deaths was 0 in each group.

No serious adverse event terms are listed. These figures describe the counts recorded for the stated groups; they do not show whether events were actively sought, how the observation period was defined, or how completeness of reporting was assessed. Those details are not reported in the registry record. General: A count of zero means no events were recorded in the specified category for the listed group. It does not establish that no event could occur, nor does it by itself establish comparative safety.

The groups received different interventions and represent different participant descriptions, and the record does not describe a randomized, like-for-like control comparison. Therefore, the adverse-event counts should be read as group-specific registry figures, not as a controlled estimate of a difference in risk between interventions.

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

The record describes a study of proposed mechanisms associated with mindfulness-based interventions and specifies an fMRI outcome for the MBCT group. It does not post a numerical primary-outcome result or a completed analysis. Consequently, the record does not establish whether the mean BOLD signal changed from baseline to 12 weeks, in which direction it changed, or how precisely any change was estimated.

The endpoint is an imaging contrast between emotional and neutral word stimuli, measured in fronto-parietal and default mode areas. It is not itself a measure of depression, anxiety, or stress symptoms. A reported change in this imaging measure would answer a question about that measure; additional evidence would be needed to connect it to clinical outcomes or to a mechanism of improvement. No such endpoint result or connection is reported in the registry record.

The study does not provide a randomized comparison in which otherwise comparable participants were assigned to MBCT or MBSR. The groups were recruited based on different participant descriptions and were receiving different interventions as standard of care. Allocation is not stated. Therefore, the record does not support attributing a difference between these groups to the intervention received.

The fMRI endpoint was assessed only in 16 participants in the mild to moderate depression and/or anxiety group. The High Stress group was not assessed with fMRI, and the record attributes that limitation to financial constraints. The overall enrollment of 136 does not change the size of the fMRI subgroup or supply missing endpoint results.

The record reports zero serious adverse events, zero other adverse events, and zero deaths in each listed group. These are descriptive counts and do not establish that an intervention is free of risk. Overall, the posted information identifies the study question and outcome definitions, but does not provide the numerical analyses needed to estimate an intervention effect or assess its precision.

13. Why This Trial Matters Statistically

This study is statistically notable for separating a proposed biological mechanism from direct clinical outcomes. Its primary endpoint concerns BOLD signal in response to emotional versus neutral words, while the study’s broader description includes neurobiological, physiological, psychosocial-behavioral, and cognitive mechanisms. Distinguishing a mechanistic measure from a symptom measure is important: they represent different kinds of evidence and do not answer the same question.

The record also illustrates how a named endpoint can be much narrower than overall enrollment. Although the study lists enrollment of 136, only 16 participants in the MBCT group participated in fMRI data collection, and the High Stress group was not assessed with fMRI. Any interpretation of the imaging question must therefore be tied to that subgroup, rather than generalized automatically to all participants or both interventions.

Design matters for interpretation as much as outcome definition. The two groups differ in participant characteristics and intervention, and allocation is not stated. The record does not describe a randomized, like-for-like control comparison. Those features limit what a direct comparison between groups could establish, even if numerical results were available.

Finally, the registry record lists five outcome measures but no analyses and no numerical primary result. This distinction is central to evidence interpretation: a defined endpoint is not the same as a reported estimate, and completion status is not evidence of a particular finding. Readers need the estimate, its uncertainty, and the analysis methods to assess what the study’s data show. Those results are not reported in the registry 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 interpreting the main endpoint is that the registry record does not report a numerical result or analysis. There is no posted estimate of the baseline-to-12-week change in BOLD signal, standard error, confidence interval, p-value, or test statistic. The record therefore does not support a conclusion about the direction, magnitude, or precision of an endpoint change.

The imaging endpoint is restricted to a small subgroup: 16 participants in the mild to moderate depression and/or anxiety group participated in fMRI data collection. Participants in the High Stress group were not assessed using fMRI, and the record attributes the smaller subgroup to financial constraints. The number with complete data at both time points and the handling of missing fMRI observations are not reported in the registry record.

The study groups do not constitute a randomized, like-for-like control comparison according to the record. They differ in participant descriptions and interventions, and allocation is not stated. This limits causal interpretation of any group difference. The record also does not report blinding, the statistical analysis plan, details of the imaging model, or how peak voxels and the reported mean score were selected or calculated beyond the brief endpoint description.

The registry lists five outcome measures but no analyses. It does not report how multiple outcomes were handled, whether analyses were adjusted, or how analysis populations were defined. The endpoint description’s reference to an SD of 2 and its interpretation of higher means are not accompanied by enough statistical detail to assess the calculation or inferential basis. These omissions leave the endpoint definition more informative than the available evidence about its result.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Mechanisms of Mindfulness-based Interventions — NCT03571386.
• Registry record last updated 2025-01-31; status last verified 2025-01.
• Results first posted 2025-01-31.
• 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

The completed study, NCT03571386, is titled “Mechanisms of Mindfulness-based Interventions” and is sponsored by Vanderbilt University Medical Center. The registry lists enrollment of 136 and conditions of depression, anxiety, and stress. Its summary describes a mixed methods investigation of proposed mechanisms of mindfulness-based interventions.

The listed interventions are MBCT and MBSR, delivered in group settings as standard of care to differently described participant groups. The primary outcome is change in BOLD mean signal from baseline to 12 weeks in response to emotional versus neutral word stimuli. Only 16 participants in the MBCT group participated in fMRI data collection; the High Stress group was not assessed with fMRI.

The record lists five outcome measures and zero analyses. It reports zero serious adverse events, zero other adverse events, and zero deaths in each group. A numerical primary endpoint estimate, uncertainty interval, and statistical analysis are not reported in the registry record.