Cognition and Psychotherapy in PTSD: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cognition and Psychotherapy in PTSD (NCT03641924), a registered phase not stated study. The primary outcome is Change in PTSD Checklist (PCL-5).

2. Clinical Question

The central question is about prediction and possible pathways, rather than a randomized test of CPT against another treatment or a control condition. The study description proposes examining whether verbal memory is associated with symptom reduction and functional outcomes, and whether recall of treatment content affects the relationship between memory functioning and outcomes. These are questions about variation in outcomes among people receiving therapy, as described by the record.

The primary outcome is change in PTSD Checklist (PCL-5) score from baseline to 12 weeks, considered in relation to baseline memory scores. The registry also lists a secondary outcome, the Veterans RAND 12 Item Health Survey Mental Component Summary (VR-12 MCS). The record does not report the results needed to determine whether memory predicted change, whether recall or engagement was associated with outcomes, or how functional outcomes varied. Nor does it report a treatment-versus-control estimate. The clinical question can therefore be described from the study aims, but its answers cannot be established from the reported numerical results.

3. Trial Design

The registry identifies NCT03641924 as “Cognition and Psychotherapy in PTSD,” with the official title “Cognition and Psychotherapy in PTSD: Mechanisms and Functional Outcomes.” The listed condition is Posttraumatic Stress Disorder (PTSD), and the sponsor is the VA Office of Research and Development. The record gives a start date of 2019-05-20, a primary completion date of 2023-09-29, and a status of COMPLETED. Enrollment is listed as 110. That enrollment figure describes the registry record and should not be taken to establish how many participants contributed to any particular outcome analysis.

Cognitive Processing Therapy is the listed behavioral intervention. The arm description identifies veterans diagnosed with DSM-V PTSD. The record does not describe a randomized allocation, and it explicitly notes that allocation was not stated and that the arms are not a like-for-like control comparison. Consequently, the design information does not support interpreting the study as a randomized controlled comparison. The registry record does not report a comparator treatment or a control condition that could be used to estimate a relative treatment effect.

The stated study aims concern whether verbal memory predicts CPT outcomes, including PTSD symptom change and functional outcomes. They also concern possible relationships among memory functioning, treatment engagement, recall of treatment content, and illness course. A specific proposed question is whether memory for treatment content affects the relationship between memory functioning and outcomes. These aims describe the intended scientific focus, not evidence that any proposed association was found.

The primary outcome is PCL-5 change from baseline to 12 weeks. The record lists the VR-12 MCS as a secondary outcome and indicates three outcome measures, but does not report numerical outcome findings or analysis results. The registry record does not report further detail about allocation procedures, masking, treatment delivery, or the analytic sample for each outcome. Those aspects should not be inferred from the intervention name, enrollment, or completed status.

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: 28 participants either did not meet criteria for PTSD after a structured assessment (n=19), met criteria for a comorbid disorder that was exclusionary (n=4), or were lost to follow-up before completing baseline assessments.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Based on baseline memory scores

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 Change in PTSD Checklist (PCL-5), measured over Change from baseline to 12 weeks.

The primary endpoint is change in PTSD Checklist (PCL-5) score from baseline to 12 weeks. The PCL-5 is described in the registry as a measure of PTSD symptoms on a scale ranging from 0 (no symptoms) to 80 (maximal symptoms); higher scores correspond to more symptoms. The recorded parameter is a mean, with standard deviation as the dispersion measure. The outcome is considered based on baseline memory scores.

Change scores are used to describe how a measured outcome differs between an initial assessment and a later assessment. In this study, the endpoint is intended to capture change in reported PTSD symptom burden over the stated period. In general, a lower follow-up score relative to baseline would correspond to fewer reported symptoms on a scale where higher scores indicate more symptoms. That general interpretation does not establish what occurred in this study: the registry record does not provide the mean change, its standard deviation, or results by baseline memory level.

Examining the endpoint in relation to baseline memory fits the stated aim of assessing verbal memory as a predictor of outcomes. It is not, by itself, a randomized comparison of treatments. Without reported estimates and their uncertainty, the magnitude, direction, and precision of any association between baseline memory and PCL-5 change cannot be determined. The registry record also does not report a clinically meaningful threshold for interpreting a change in PCL-5 score, so a numerical change cannot be classified against such a threshold from this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is continuous: it is a mean change in PCL-5 score, and the registry identifies standard deviation as its dispersion measure. For a continuous outcome, a mean describes the center of the observed scores or changes, while a standard deviation describes their spread. The mean can make group-level patterns easier to summarize, but it does not show how every participant changed. The standard deviation is not a measure of uncertainty in the mean; it describes variability among observations. The registry record does not report either numerical quantity for the primary endpoint.

What would a confidence interval add?

In general, a confidence interval expresses the uncertainty around an estimated quantity under the assumptions of the analysis. A relatively narrow interval indicates greater precision than a wide interval, while both the estimate and interval are needed to understand the plausible range of values consistent with the data and method. A confidence interval does not show the probability that a particular treatment effect is true. No confidence interval for the primary endpoint or its relationship with baseline memory is reported in the registry record. Therefore, precision cannot be judged from the endpoint definition or enrollment alone.

How should change be interpreted?

A change score compares a measurement at follow-up with a measurement at baseline. Here, the registered interval is baseline to 12 weeks. Because higher PCL-5 scores correspond to more symptoms, the direction of a reported change would matter: a change toward lower scores would indicate fewer symptoms on the scale, while a change toward higher scores would indicate more symptoms. This is general interpretation of the scale, not a statement about this study's results. The registry record does not report the observed mean change or its distribution.

What does the memory question imply statistically?

The stated question treats baseline memory as a potential predictor of later outcome. In general, prediction asks whether outcome values vary in a systematic way with a predictor. An association can be estimated in different ways, but the registry record does not report the specific model, covariates, memory measure definition, or functional form used. It is therefore not possible to tell whether the proposed relationship was modeled as a difference between memory categories, a continuous trend, or another specification. A predictive association also differs from a causal effect: it does not establish that changing memory would change treatment outcomes.

The study description proposes examining treatment engagement and recall of treatment content as possible links between memory functioning and outcomes. In general, a pathway analysis asks whether observed relationships among variables are consistent with a proposed sequence. Such an analysis depends on how each variable is measured, the timing of its measurement, the model, and assumptions about other influences. Those details and the corresponding results are not reported in the registry record, so the proposed pathways cannot be evaluated from the posted information.

What is the role of the planning illustration?

The record describes sample-size 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. The effect to detect is described as a stated fraction of the observed effect. These are planning assumptions, not a description of the trial's own design or proof that the study had a particular probability of detecting an effect. Sample-size illustrations are planning quantities, never “observed power.” The record does not provide numeric estimates for those illustrations in the registry record for this analysis, and no planning value should be mistaken for an observed outcome.

The stated equal-allocation, two-arm assumption is a calculation convention for the planning illustration. It does not override the registry's design caution that allocation was not stated and that the arms are not a like-for-like control comparison. Nor does it establish that the trial actually enrolled or analyzed participants in equal groups. The registry record does not report an analysis-specific allocation or denominator.

In general, over-dispersion means that observed variability is greater than a model's assumed variability. If a model fails to account for that extra variation, its uncertainty estimates can be too small and its tests can appear more decisive than warranted. This is a general statistical consideration; the registry record does not report a model or evidence of over-dispersion for this trial. Likewise, the entry does not report the assumptions, diagnostics, or sensitivity checks used for any outcome analysis. Without estimates, model specifications, and uncertainty measures, readers cannot assess whether a particular statistical method was appropriate or how robust an estimate might be.

The registry lists zero analyses and supplies no numerical primary outcome results. Consequently, statistical methods can be explained in general and the planning assumptions can be described, but the trial's actual outcome analysis cannot be reconstructed or independently assessed from the registry information.

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("Low Memory", "Medium Memory", "High Memory")
n   <- c(31, 32, 31)
m   <- c(9.25, 11.94, 15.91)
sp  <- c(20.37, 15.93, 15.1)
sd  <- sp      # posted standard deviations
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  Low Memory  31  9.250  20.370  1.778  16.722
CARM  Medium Memory  32  11.940  15.930  6.197  17.683
CARM  High Memory  31  15.910  15.100  10.371  21.449

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary PCL-5 change outcome and a secondary VR-12 MCS outcome, and indicates three outcome measures. Considering multiple outcomes or multiple analyses can raise a multiplicity issue: when many hypotheses are tested, the chance of at least one apparently notable result can increase. In general, a prespecified outcome hierarchy or adjustment method can help readers understand how multiple comparisons were handled. The registry record does not report a multiplicity strategy, a testing hierarchy, or an adjustment method. It also lists zero analyses, so no set of reported tests is available to evaluate.

The record does not report how missing baseline or follow-up measurements were handled, whether analyses used all available observations or a defined analysis population, or whether any imputation or sensitivity analysis was used. These details matter because incomplete outcome data can affect both the estimate and its precision. If missingness is related to symptoms, memory, treatment engagement, or other factors, the analyzed observations may differ systematically from those without observed outcomes. This is a general concern, not a finding about this study.

Enrollment is listed as 110, but the registry does not give the number contributing to each outcome analysis or explain exclusions from analyses. The record also does not report whether analysis populations were defined in advance. Thus, neither the enrollment entry nor the completed status resolves questions about missing data, analysis denominators, or population definitions. These items are not reported in the registry record, and their potential effects on the results cannot be assessed.

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 serious adverse event entry lists 94 at risk and 0 affected for the PTSD group. The other-event entry also lists 94 at risk and 0 affected, and deaths are listed as 0. The registry record gives no serious adverse event terms in its list of top terms. These figures should be read as the safety fields recorded in the entry, not as evidence that every possible adverse event was assessed or that no unlisted event occurred.

The two at-risk entries belong to separate serious-event and other-event fields; they should not be added or interpreted as a count of distinct participants. The registry record does not report event definitions, collection procedures, the period of safety surveillance, or additional detail about the completeness of safety reporting. It also does not provide a comparison that would support a relative safety estimate. The zero affected counts are therefore limited to the specific registry fields and should not be taken as a complete characterization of safety or as a comparison of CPT with another intervention.

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

The registry record documents a study designed to examine whether verbal memory predicts PTSD symptom and functional outcomes in the context of cognitive processing therapy. It defines the primary outcome as PCL-5 change from baseline to 12 weeks and gives the scale's range and direction. It also identifies the proposed role of treatment engagement and recall of treatment content in understanding possible relationships between memory functioning and outcomes. These details explain the scientific question; they do not answer it.

No numerical primary outcome result is reported in the registry record. Without a mean change, standard deviation, estimate by baseline memory, and measure of uncertainty, the amount and precision of any change or association cannot be described. The registry also does not provide numerical results for the listed secondary outcome. The record's completed status and enrollment figure do not substitute for those findings.

The design note further limits what can be inferred. Allocation is not stated, and the arms are not described as a like-for-like control comparison. The available information therefore does not establish a randomized contrast or a causal effect of CPT relative to another condition. The study's predictor and pathway questions are observational in interpretation unless supported by an appropriate design and analysis; the registry entry does not report the analysis details needed to assess them.

These limitations do not mean that the study failed to answer its research questions. They mean that the answers are not available in the outcome information reported in this registry record. Readers can identify the planned clinical focus, the endpoint definition, and some design and safety entries, but cannot determine the size, direction, statistical precision, or clinical importance of the primary outcome from this record. No treatment recommendation follows from the information reported.

14. Why This Trial Matters Statistically

This trial is statistically notable for asking a prediction and mechanism question rather than presenting a randomized comparison of treatment options. The stated focus is whether baseline verbal memory predicts symptom and functional outcomes, with engagement and recall of treatment content considered as possible links. Such questions can help distinguish whether outcomes vary with participant characteristics from whether one treatment outperforms another. The registry design note is important: allocation was not stated, and the arms are not a like-for-like control comparison.

The primary endpoint is a continuous measure of change in PTSD symptoms, considered in relation to baseline memory. That framing makes the estimated relationship and its uncertainty central. A result would need to communicate not only whether an association was detected, but also its size and precision, and how it was modeled. The registry record does not report those results, so the statistical contribution cannot be judged from the posted outcome information.

The study also illustrates why protocol aims, outcome definitions, and reported findings should be kept distinct. The description proposes examining symptom reduction, functional outcomes, engagement, recall, and illness course. The endpoint definition gives a measurement framework, but does not establish that any proposed pathway was observed. The entry lists a secondary outcome and three outcome measures, yet reports zero analyses. Without analysis results, multiplicity handling, missing-data methods, and analysis populations, readers cannot assess the robustness or scope of findings.

Finally, the planning description should not be confused with evidence about the trial's achieved precision. The stated sample-size illustrations are based on an observed effect and specified calculation assumptions, but sample-size planning is not observed power and does not replace confidence intervals around actual estimates. In this registry record, the lack of numerical outcome results prevents evaluation of both effect magnitude and precision. That distinction is essential when interpreting a completed study whose registry entry does not include its outcome estimates.

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 registry record offers limited detail for evaluating the study's design and results. It states that allocation was not reported and cautions that the arms are not a like-for-like control comparison. It does not describe a randomized comparator, so a treatment-versus-control effect cannot be inferred from the record. The intervention is identified as CPT, but details about how treatment was delivered or assessed are not reported.

The primary endpoint is defined, but its numerical findings are absent. The record does not report the mean PCL-5 change, its standard deviation, estimates according to baseline memory, or uncertainty measures. Numerical results for the secondary VR-12 MCS outcome are also not reported. Although enrollment is listed as 110, outcome-specific analysis counts and participant flow are not reported, so the enrolled figure cannot establish the denominator for any result.

Important analytic details are not reported in the registry record, including the model used to assess memory as a predictor, the definition and measurement of memory, handling of missing observations, analysis populations, multiplicity procedures, and sensitivity analyses. The registry lists zero analyses. Without these details and results, readers cannot assess model assumptions, the influence of incomplete data, or whether findings were consistent across outcomes or analytic choices.

The stated study aims include several related outcomes and possible pathways, but the registry entry does not show which analyses were completed or how findings were interpreted. The safety fields list zero affected for serious events and other events, but do not provide definitions or surveillance details. These limitations constrain interpretation of both efficacy-related questions and safety reporting. They identify gaps in the registry information; they do not establish that the underlying study did not collect or analyze these data.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Cognition and Psychotherapy in PTSD — NCT03641924.
• Registry record last updated 2025-05-09; status last verified 2025-05.
• Results first posted 2025-05-09.
• 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

NCT03641924 is a completed registry record for “Cognition and Psychotherapy in PTSD,” sponsored by the VA Office of Research and Development. It lists PTSD as the condition, CPT as the behavioral intervention, enrollment of 110, a start date of 2019-05-20, and a primary completion date of 2023-09-29.

The study aims concern whether verbal memory predicts PTSD symptom and functional outcomes and whether treatment engagement and recall of treatment content relate to those outcomes. The primary endpoint is PCL-5 change from baseline to 12 weeks, with the VR-12 MCS listed as a secondary outcome. Allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison.

Numerical primary and secondary outcome findings, analysis details, missing-data methods, and multiplicity procedures are not reported in the registry record. The entry lists zero analyses. Its safety fields list 0 affected for serious events, 0 affected for other events, and 0 deaths.