Meditation Interventions for Treatment of PTSD in Veterans: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Meditation Interventions for Treatment of PTSD in Veterans (NCT01548742), a randomized na study. The primary outcome is PTSD Symptoms on the PTSD Checklist (PCL) at Baseline, During Treatment, After Treatment and at 2-Month Follow-up.

2. Clinical Question

The clinical question is whether the two group-based approaches differ in measured PTSD symptom severity over the assessment schedule. The PCL is a self-reported symptom measure; its score range and the registry’s stated clinically important reduction are described with the endpoint. That threshold gives context for interpreting a change in an individual score, but it does not establish a treatment-group difference or substitute for a reported analysis.

The record names secondary measures of PTSD symptom severity on the Clinician Administered PTSD Scale (CAPS) and depression symptom severity on the Patient Health Questionnaire-9 (PHQ-9), each listed at baseline, after treatment, and at 2-month follow-up. The registry record does not report results for these measures. Without outcome estimates and their uncertainty, the clinical question cannot be answered from the posted results.

3. Trial Design

The registry describes a randomized, double-masked, parallel-group trial comparing Mindfulness-Based Stress Reduction (MBSR) with Present-Centered Group Therapy (PCGT). Both interventions are classified as behavioral. The study title and summary identify veterans with PTSD as the population of interest. The record lists enrollment as 116 and status as completed. Enrollment in the registry should not be taken as a statement about how many participants contributed outcome data at any particular assessment.

The sponsor is the VA Office of Research and Development. The recorded study start is 2012-03, and the primary completion date is 2014-06. The phase is recorded as NA. The registry does not report the allocation ratio, the details of sequence generation, or the procedures used to maintain masking. It also does not report whether participants or treatment providers could identify the assigned intervention. The label double-masked is recorded, but the specific roles masked are not described.

The primary outcome is PCL symptom severity, with assessments specified at baseline, Weeks 3, 6, 9 and 17. The primary outcome title also describes baseline, during-treatment, after-treatment and 2-month follow-up assessments. The relationship between those descriptions and the named weeks is not explained in the registry record. Secondary outcomes are listed for CAPS and PHQ-9 at baseline, after treatment, and at 2-month follow-up; corresponding results are not reported.

The record identifies an intent-to-treat population for the primary outcome, defined as all participants randomized to treatment. It does not describe the analysis model, handling of missed visits, or any departures from the intended population. The record reports no analysis results for the primary endpoint, so the design information describes the planned comparison rather than an estimate of its outcome.

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: Participants completed a 5-hour eligibility and baseline assessment that included a structured clinical interview and self-report measures. Randomization occurred for those meeting study inclusion criteria.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Intent to treat population (all participants randomized to treatment).

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 PTSD Symptoms on the PTSD Checklist (PCL) at Baseline, During Treatment, After Treatment and at 2-Month Follow-up, measured over Baseline, Weeks 3, 6, 9 and 17.

The primary endpoint is PTSD symptom severity measured with the PTSD Checklist (PCL). The registry describes the PCL as a valid and reliable measure of PTSD symptoms and reports a score range of 17-85, with higher scores indicating more severe symptoms. It also states that a reduction of 10 or more points is the minimal clinically important difference for self-reported PTSD symptom severity.

Repeated PCL assessments are intended to characterize symptoms across treatment and follow-up, rather than at a single visit alone. The primary outcome title refers to baseline, during treatment, after treatment and a 2-month follow-up; the stated timeframe names baseline and Weeks 3, 6, 9 and 17. The registry does not explain how these descriptions correspond, nor does it report estimates at those visits.

Using a recognized symptom measure makes the outcome interpretable in terms of the construct being studied: self-reported PTSD symptom severity. The stated clinically important reduction offers a reference for judging the size of a change in an individual score. It is not itself evidence that either group achieved that change, and it does not tell whether the groups differed. Those judgments require the observed results, an appropriate comparison, and uncertainty estimates, which are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean describe?

The primary outcome is a continuous measure, and the registry identifies the mean as its summary parameter. In general, a mean describes the average score in the observations included in an analysis. It does not show the full distribution of scores: participants can have quite different scores even when their group mean is the same. A mean at a follow-up visit also does not, by itself, describe change from baseline or a difference between randomized groups.

For a comparison, the key quantity is the contrast the analysis was designed to estimate. It might compare group means at a particular assessment, compare changes from baseline, or model the pattern across repeated assessments. These approaches answer related but not identical questions. The registry record does not report which contrast or statistical model was used, or provide any primary-outcome mean estimates.

How should a confidence interval be read?

The primary outcome lists a 95% confidence interval as its measure of dispersion. In general, a confidence interval describes statistical uncertainty around an estimated quantity under the assumptions of the method used. Its endpoints indicate a range of values compatible with the data and model at the stated confidence level. The interval is not a measure of the spread of individual participants’ scores, and it does not guarantee that the true value lies within the observed interval.

For an estimated difference between groups, the interval’s location and width are important. The location indicates the range of plausible values for the contrast; the width indicates its precision. A narrow interval is more precise than a wide interval, while an interval that includes values representing little or no difference may leave the direction or size uncertain. These are general principles. The registry does not report the estimates or intervals needed to apply them to this comparison.

Why do repeated assessments matter?

The PCL is planned at baseline and at several subsequent assessments. Repeated measurements can describe the course of symptoms and allow assessment of whether groups follow different patterns. Measurements from the same participant are generally related, rather than independent. In general, a repeated-measures analysis should account for that within-participant relationship; treating related observations as unrelated can misstate uncertainty.

The record’s primary outcome title and timeframe describe the assessment schedule differently: the title refers to baseline, during treatment, after treatment and at 2-month follow-up, while the timeframe names baseline, Weeks 3, 6, 9 and 17. The registry does not explain the mapping or specify which visits define the main contrast. A reader therefore cannot identify the intended primary time point or trajectory comparison from the record alone.

What does intent-to-treat mean?

The primary outcome population is described as intent to treat, defined in the record as all participants randomized to treatment. In general, this approach aims to retain participants in their randomized groups for analysis, regardless of whether they completed or adhered to the assigned intervention. Preserving the randomized comparison can help avoid bias that may arise if groups are redefined according to treatment received or completion.

The label alone does not explain how missing outcome measurements were handled. An analysis may include all randomized participants in its target population while still requiring assumptions or methods for unobserved measurements. The registry does not report the number with observed PCL data at each assessment, reasons for missingness, imputation methods, or sensitivity analyses. The actual implementation of the stated intent-to-treat population is therefore not assessable from the record.

How should planning illustrations be interpreted?

In general, a sample-size calculation asks how much information a future study would need to target a specified effect under stated assumptions. The planning assumptions associated with this trial describe a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect expressed as a fraction of an observed effect. The illustrations are planning calculations, not observed power and not evidence about the trial’s outcome.

The record does not report the numerical observed effect or the calculated planning values in the material describing the assumptions. No planning value should be treated as an outcome estimate or as a design fact about how this trial was originally sized: the registry explicitly characterizes the calculation as a planning illustration based on the observed effect, not the trial’s own design. The trial’s sample-size justification is not reported in the registry record.

What can be concluded from the analysis record?

The registry records 0 analyses and does not provide primary-outcome estimates. This is a reporting limitation for statistical interpretation: without the analysis results, readers cannot evaluate the direction or magnitude of an estimated difference, the precision of that estimate, or whether it meets a stated threshold. General statistical principles can clarify what such information would mean, but they cannot replace the missing results.

The record also does not report the model specification, covariate adjustment, handling of repeated measurements, or treatment of missing data. Nor does it describe an interim analysis or a statistical analysis plan. These methods can influence estimates and uncertainty, particularly when outcome measures are collected repeatedly. Their absence means that the analytical choices cannot be checked against the planned comparison. No particular method or unreported procedure should be assumed.

10. Multiplicity, Missing Data and Analysis Populations

The primary PCL outcome has multiple assessment times, and the registry lists secondary outcomes for PTSD symptoms on the CAPS and depression symptoms on the PHQ-9. When many outcomes, visits, or contrasts are examined, the chance of obtaining at least one apparently notable result by chance can increase. In general, a statistical plan may identify a primary contrast or use other approaches to address multiplicity. The registry record does not report a multiplicity strategy, a hierarchy of comparisons, or which time point is intended to anchor the primary conclusion.

The analysis count is recorded as 0, and no estimates or inferential results are reported for the primary or secondary outcomes. The registry record therefore does not allow readers to assess which comparisons were actually conducted or how multiplicity was handled. It also does not report whether interim analyses were planned or performed.

The stated primary population is intent to treat, defined as all participants randomized to treatment. However, the registry does not provide assessment-specific observed counts, reasons for missing data, or methods used to handle missingness. In general, incomplete repeated measurements can affect both the estimated group contrast and its precision, particularly if the likelihood of missing data differs according to symptoms or treatment experience. The record does not describe imputation, model assumptions for incomplete data, or sensitivity analyses.

Consequently, the intended analysis population is named, but the completeness of the endpoint data and the implementation of the analysis are not assessable. Missing-data handling and multiplicity procedures are not reported in the registry record.

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.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: suicide attempt or worsening of symptoms (1.7%), crushed by falling tree (1.7%).

The registry reports serious adverse events separately for the two intervention groups. For MBSR, 1 of 58 participants at risk was affected by a serious adverse event; for PCGT, 2 of 58 participants at risk were affected. The record lists 0 participants with other adverse events among 58 at risk in each group. Death counts are not reported in the registry record.

The serious-event terms listed include Suicide Attempt or worsening of symptoms at 1.7% and Crushed by falling tree at 1.7%. These are registry entries; the record does not provide additional event-level context or explain whether a listed term represents one event or a broader grouping. The percentages should be understood as reported, not recalculated or used to infer details not stated in the record.

These entries are descriptive counts, not a statistical comparison establishing a difference in safety between interventions. Small event counts can be imprecise, and the registry does not report a comparative analysis or uncertainty interval for these outcomes. The count of zero for other adverse events means none were recorded in that category in this entry; it does not establish that no other event occurred or that no event was missed. The record does not provide further information about severity, timing, relatedness, or follow-up for the listed events.

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

The registry record describes a randomized, double-masked, parallel-group study of MBSR compared with PCGT in veterans with PTSD. It identifies PCL symptom severity as the primary outcome and specifies repeated assessments. It also lists secondary PTSD and depression measures and reports serious adverse-event counts. These details establish what the study set out to examine and what was entered into the registry.

The record does not report primary-outcome analyses or estimates. It therefore cannot show whether average PCL scores differed between groups, how scores changed over time, or how precise any such difference might be. It also cannot establish whether a change reached the stated clinically important reduction of 10 or more points. The completed status of the study does not supply those missing statistical results.

Conversely, absence of outcome analyses in the registry record is not evidence that the treatments had the same effect or that there was no change in symptoms. It means the record does not provide the information needed to evaluate those possibilities. A sound comparison would require the relevant group estimates or contrast, uncertainty intervals, and an account of the analysis population and missing measurements.

The serious adverse-event entries describe reported events, not a complete safety comparison. The registry lists counts and event terms, but it does not report a statistical assessment of differences or enough detail to establish event attribution. The entries should not be interpreted as proof of either safety or harm beyond what the record states.

In short, the study’s design and outcome definitions are available, while its comparative symptom findings are not reported in the registry record. Any claim about relative benefit, lack of benefit, or clinical effectiveness would go beyond these posted data.

13. Why This Trial Matters Statistically

This study is statistically notable as a randomized comparison of two behavioral group interventions with repeated measurement of PTSD symptom severity. The design raises questions common to clinical research: how to compare group trajectories, account for related measurements from the same participant, and interpret a continuous symptom scale in relation to a clinically meaningful threshold.

The registry identifies an intent-to-treat population and names a confidence interval for the primary measure. Those choices point to important elements of rigorous interpretation: maintaining the randomized comparison, reporting an effect estimate, and showing the uncertainty around it. But the record does not include the results or explain the model, missing-data approach, or primary contrast. Readers therefore cannot assess whether the intended statistical questions were answered in the analysis.

The multiple assessment times and listed secondary measures also make multiplicity relevant. Without a reported plan for prioritizing comparisons or handling multiple analyses, readers cannot distinguish a prespecified primary finding from a result selected after examining several possibilities. The registry record does not report such a plan or analyses.

The record’s limits are themselves informative for statistical reading. A completed trial entry, intervention descriptions, and a defined endpoint do not replace comparative estimates. The distinction between a study being designed to answer a question and a registry record reporting an answer is essential. Here, the design can be described, but the primary outcome’s direction, size, and precision cannot be assessed from the posted results.

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.

Several trial-specific details needed to interpret the planned comparison are not reported in the registry record. Although the study is described as randomized and double-masked, the record does not state how the random sequence was generated, how assignments were concealed, or which people were masked. The allocation ratio and practical procedures for maintaining masking are also not described. These omissions limit assessment of how the design was implemented.

The primary outcome schedule has two descriptions: the title refers to baseline, during treatment, after treatment and 2-month follow-up, while the timeframe names baseline and Weeks 3, 6, 9 and 17. The registry does not explain how the visit labels correspond or identify the primary time-point contrast. It also does not report PCL results at any of the named assessments.

The record does not provide detail on treatment attendance, adherence, withdrawals, or the number with outcome data at each visit. It does not describe methods for missing data, the model used for repeated assessments, covariate adjustment, or sensitivity analyses. The intent-to-treat population is stated, but its implementation cannot be checked against participant-level analysis counts.

The analysis count is recorded as 0, and multiplicity procedures, interim analyses, and the statistical analysis plan are not reported. Sample-size justification is not reported in the registry record; the planning assumptions describe an illustration based on an observed effect rather than the trial’s own design. Finally, serious adverse-event details are limited to counts and terms, with deaths not reported. These limitations concern what can be assessed from the registry entry and should not be taken as evidence about unreported trial procedures or outcomes.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Meditation Interventions for Treatment of PTSD in Veterans — NCT01548742.
• Registry record last updated 2015-12-10; status last verified 2015-11.
• Results first posted 2015-12-10.
• 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 identifies NCT01548742 as a completed, randomized, double-masked, parallel-group study comparing Mindfulness-Based Stress Reduction with Present-Centered Group Therapy for veterans with PTSD. Enrollment is listed as 116, and the sponsor is the VA Office of Research and Development. The recorded study start is 2012-03, with primary completion at 2014-06.

The primary outcome is PCL symptom severity, with the record naming a mean and 95% confidence interval and listing repeated assessments. Secondary measures are CAPS PTSD symptom severity and PHQ-9 depression symptom severity. The record describes an intent-to-treat population for the primary outcome.

Primary and secondary outcome analyses are not reported in the registry record. The entry includes serious adverse-event counts by group and lists serious-event terms, while death counts are not reported. The record does not provide the statistical plan, missing-data methods, or multiplicity approach needed to evaluate the analyses.