Cognitive Behavior Therapy for Work Success in Veterans With Mental Illness: A Pre-post Efficacy Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cognitive Behavior Therapy for Work Success in Veterans With Mental Illness: A Pre-post Efficacy Study (NCT01918774), a na na study. The primary outcome is Change in Competitive Employment.

2. Clinical Question

3. Trial Design

The registry identifies this study as a completed, open trial with a single-group design. Its title describes a pre-post efficacy study, and the primary outcome is framed as change in competitive employment from baseline to the 6 month follow-up. There is no randomized allocation or masked assessment reported. No separate comparison arm is described, so the design relies on measuring participants at different times rather than comparing outcomes between treatment groups.

The intervention is CBTw, a behavioral intervention. The arm description says participants would take part in a 12 week program and receive standard SE services during the study. The record does not report the delivery format, session frequency, adherence, or whether participants received other services. It also does not report the timing of assessments beyond the stated baseline-to-follow-up comparison for the primary endpoint.

The registry lists enrollment as 57. The intervention description refers to fifty participants as planned for the program, while the safety record lists 52 participants at risk. These figures represent different record entries; their relationship is not explained in the registry record. They should not be treated as interchangeable denominators. The primary outcome population is described as all participants who completed the study, but the number of completers included in that analysis is not reported.

The record lists the study as completed, with a start date of 2016-02-01 and a primary completion date of 2018-07-31. The phase and allocation entries are listed as NA. The registry record does not report a protocol-based sample-size justification, interim analysis plan, or detailed statistical analysis plan. The single-group design can describe change over time, but without a concurrent control group it cannot separate intervention-associated change from other explanations for change.

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: Open trial treatment, all participants who completed the study are included.

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: Study completers

6. Primary Endpoint

The registry lists the primary outcome as Change in Competitive Employment, measured over Change from baseline competitive employment to 6 month follow up competitive employment.

The primary endpoint is change in competitive employment, measured as the change in the total number of weeks worked in competitive jobs between baseline and the 6 month follow-up. Its unit is weeks, and the registry describes the measure as a mean with standard deviation. The endpoint therefore summarizes work duration as a continuous outcome rather than as a simple employed-or-not-employed status.

Competitive employment is described in the registry as a standard outcome in studies of employment among people with mental illness. Counting weeks worked can capture duration of work over the assessment period, including differences that a single status assessment might not convey. However, interpretation depends on the exact assessment window, how competitive jobs were defined, and how work histories were collected. Those operational details are not reported in the registry record.

The endpoint is described as a change from baseline to follow-up, but the record does not report the mean change, its standard deviation, a confidence interval, or a test result. It also does not report the number of participants with usable endpoint data. As a result, the endpoint's observed magnitude and precision cannot be evaluated from the registry record. The stated measure identifies what the study intended to assess, not what the observed result was.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a pre-post estimate describe?

In a pre-post study, the outcome is measured at baseline and again at follow-up, and the analysis describes how the measurements differ over time. Here, the primary measure is the change in total weeks worked in competitive jobs between baseline and the 6 month follow-up. A mean change would describe the average change among the participants included in that analysis. It would not, on its own, show what would have happened to those participants over the same period without the intervention.

General statistical explanation: a change estimate is most informative when the outcome definition, assessment window, analysis population, and method for handling incomplete observations are clear. The registry record states the intended endpoint and identifies participants who completed the study as the primary outcome population, but it does not provide the observed estimate or the details needed to reconstruct the analysis.

What does a standard deviation convey?

The registry describes the primary outcome as a mean with standard deviation. A mean summarizes the central value of a continuous measure, while a standard deviation describes how spread out individual values are around that mean. The standard deviation is not the same as the uncertainty in the estimated mean. The latter depends on the amount of information in the analysis and is commonly conveyed with a confidence interval. Neither the primary outcome mean nor its standard deviation is reported in the registry record.

General statistical explanation: work-week outcomes may have a distribution in which many participants have similar values while some have substantially different values. If the data are strongly skewed or contain influential observations, a mean and standard deviation may not fully describe the distribution. The record does not provide outcome distributions or alternative summaries, so it is not possible to assess whether the chosen summary was adequate for the observed data.

How should uncertainty be assessed?

A confidence interval is a range of values compatible with the data under the statistical model used. It conveys uncertainty about an estimate and can help distinguish a precisely estimated change from one with substantial uncertainty. A p-value, when reported, addresses compatibility with a specified null model; it does not measure the size or practical importance of a change. Neither a confidence interval nor a p-value for the primary outcome is reported in the registry record.

General statistical explanation: statistical significance and practical importance are different questions. The size and context of an estimated change matter, as does its precision. Since no estimate or uncertainty measure is reported, neither question can be answered for the primary endpoint from this record.

Why does the single-group design matter?

A concurrent comparison group can help account for changes that would have occurred over time without the intervention. This study is listed as a single-group design, with no randomized comparison. A pre-post difference in this setting may be influenced by the intervention, standard SE services, changes in personal circumstances, broader employment conditions, or other time-related factors. These are general design considerations, not evidence that any particular factor affected this study.

The open-label status means masking is listed as none. The record does not describe whether outcome collection was based on participant reports, records, or another source, nor whether assessors were independent. If measurement depends on judgment or recall, awareness of treatment can sometimes influence reporting or assessment; whether that issue arose is not reported.

What do the planning assumptions mean?

The registry includes assumptions for a planning illustration based on the observed effect: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It describes the effect to detect as a stated fraction of the observed effect. These are planning assumptions rather than a description of this study's single-group design. The record does not provide specific calculated sample-size values in the registry record for this analysis, and the illustration should not be read as observed power or as the study's original design justification.

General statistical explanation: planning calculations ask how much information a future study might need under stated assumptions. They do not establish the probability that a completed study has detected an effect, and they do not replace estimates and uncertainty from the observed data. Since the primary outcome result is not reported, the observed effect on which the illustration is said to be based cannot be evaluated from the registry record.

What is not reported about the analysis?

The record does not report the test used for the primary endpoint, the handling of repeated or incomplete measurements, the model covariates, or assumptions checks. It does not report a detailed statistical plan or whether any analyses were prespecified beyond the endpoint description. It also does not report whether the estimate was adjusted or unadjusted. These omissions prevent a detailed audit of the analysis and mean that no recalculation from summary statistics is possible.

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("Cognitive Behavioral Therapy for Work Success")
n   <- c(52)
m   <- c(13.6)
sp  <- c(11.2)
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  Cognitive Behavioral Therapy for Work Success  52  13.600  11.200  10.482  16.718

11. Multiplicity, Missing Data and Analysis Populations

The registry lists twelve outcome measures, including the primary employment outcome and secondary measures of work effectiveness, symptoms, self-efficacy, quality of life, motivation, and self-esteem. It lists one analysis, but does not explain which outcome or model that entry refers to, what hypotheses were tested, or whether the analysis listing is complete. Any method for controlling the chance of false-positive findings across multiple outcomes is not reported in the registry record. No outcome-specific statistical results are available to interpret.

The primary outcome population is described as all participants who completed the study. The number of completers contributing data to the primary analysis is not reported. The record does not state how many participants had baseline or follow-up outcome data, the reasons for missing data, or whether participants who did not complete the study were included in any analysis.

The method for handling missing outcomes is not reported in the registry record. It is therefore not possible to determine whether the analysis used complete cases, imputation, a model that included incomplete records, or another approach. General statistical explanation: missingness can affect both the precision and the interpretation of an estimate, particularly if the likelihood of having observed data is related to the outcome. The record does not contain information to assess that possibility.

The registry's description of the analysis population should not be taken as evidence that missing data were absent or that any particular missing-data method was used. The analysis population definition, multiplicity procedure, and sensitivity analyses are not reported in enough detail to evaluate their influence on the findings.

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 safety entry lists the CBTw group with 52 participants at risk. It records zero serious adverse events, zero other adverse events, and zero deaths. No serious adverse event terms are listed. These entries describe what the safety record reports; they do not provide event narratives, severity details beyond the serious-event category, or information about the observation period.

The safety denominator of 52 differs from the registry enrollment entry of 57 and the intervention description's statement that fifty participants would take part. The registry record does not explain the relationship among these entries. They should not be combined or treated as if they describe an identical analysis population.

General statistical explanation: a recorded count of zero means no events were entered in that category for the stated safety entry. It does not establish that the risk is absent, and interpretation depends on event definitions, ascertainment, follow-up, and the population monitored. Those details are not reported in the registry record. The safety counts also do not establish whether the intervention caused or prevented any event.

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

The record establishes that a completed, open, single-group study evaluated CBTw in Veterans with mental illness and specified change in competitive employment as its primary outcome. That outcome was defined as change in total weeks worked in competitive jobs from baseline to the 6 month follow-up. The record also describes standard SE services alongside the 12 week CBTw program.

The record does not report the observed primary outcome result. It therefore does not establish whether weeks worked increased, decreased, or remained similar, nor how precisely any change was estimated. The absence of an outcome result should not be interpreted as evidence of no change. Secondary outcome results are also not reported in the registry record.

Even if a pre-post change were available, the study design would support description of change over time more directly than a causal claim about CBTw. Participants received standard SE services as well as CBTw, and no separate control group is described. General statistical explanation: without a concurrent comparison group, it is difficult to distinguish intervention-associated change from other influences over time. The record does not report a method that addresses this limitation.

The stated analysis population includes participants who completed the study, but the number analyzed and the handling of missing outcomes are not reported. This limits assessment of how well the analyzed participants represent everyone enrolled. The record also does not give the outcome definitions and analysis details needed to independently assess the measurement and statistical methods.

The safest interpretation is consequently narrow: the registry documents the study design, intervention, intended endpoint, and safety counts, but not the numerical efficacy results. It cannot support a conclusion about the magnitude or precision of change in competitive employment, or about the causal effect of CBTw.

14. Why This Trial Matters Statistically

The study addresses an outcome with direct relevance to vocational functioning: weeks worked in competitive employment. Treating work duration as a continuous measure can represent more variation than a simple employment-status category. The endpoint also makes the time comparison explicit, from baseline to the 6 month follow-up.

Statistically, the study illustrates the distinction between measuring change and estimating a treatment effect. Repeated measurement in a single group can characterize what happened to participants over time, but it does not provide the counterfactual comparison needed to attribute that change to the intervention. The presence of standard SE services alongside CBTw adds another reason that a change could not be assigned to CBTw alone from this design.

The record is also a reminder that a clearly named endpoint is not enough to evaluate results. Interpretation requires the observed estimate, a measure of uncertainty, an analysis population, and details about missing data and analysis methods. Those results and details are not reported in the registry record. Consequently, readers cannot assess the size, precision, or robustness of the employment outcome from this record.

Finally, the record distinguishes enrollment, planned program participation, and the safety population through separate entries, without explaining how they relate. Keeping those denominators separate is important when interpreting outcome and safety information. The registry's entries are useful for understanding the intended study structure, but the missing outcome and analysis details sharply limit statistical conclusions.

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 main trial-specific limitation is the single-group pre-post design. Without a concurrent control group, any observed change in weeks worked would be difficult to separate from other influences over time. The open-label status adds the possibility that expectations or awareness could affect self-reported or assessed outcomes, although the measurement source and assessor procedures are not reported.

The intervention was delivered alongside standard SE services. The record therefore does not permit a separate estimate of the contribution of CBTw. Intervention fidelity, attendance, completion, and variation in services are not reported, limiting assessment of what participants actually received.

The primary outcome is described as a change in weeks worked, but operational details are not reported. The registry record does not explain the employment verification method, the precise interval used to count weeks, or how partial or interrupted work was handled. The number of participants contributing primary endpoint data and the missing-data approach are also not reported.

The record does not provide the primary outcome estimate, variability, confidence interval, or test result. It also does not report the detailed statistical model, assumption checks, prespecification details, or sensitivity analyses. Results for the listed secondary measures are not reported, and the approach to multiplicity is not described.

Finally, the registry lists enrollment as 57, the intervention description refers to fifty planned participants, and the safety entry lists 52 at risk. Their relationship is not explained, so these figures cannot be treated as a single denominator. Participant characteristics and the extent to which the study population represents other Veterans with mental illness are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Cognitive Behavior Therapy for Work Success in Veterans With Mental Illness: A Pre-post Efficacy Study — NCT01918774.
• 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.

19. Record Summary

The registry record describes a completed, open, single-group pre-post study of CBTw for Veterans with mental illness. The intervention description states that participants would take part in a 12 week program and receive standard SE services. The primary endpoint is change in total weeks worked in competitive jobs from baseline to the 6 month follow-up, summarized as a mean with standard deviation.

The record lists enrollment as 57 and identifies participants who completed the study as the primary outcome population. It does not report the number included in the outcome analysis or the observed primary endpoint result. The statistical test, uncertainty estimate, missing-data approach, and multiplicity procedure are not reported in the registry record.

The safety entry lists 52 participants at risk, zero serious adverse events, zero other adverse events, and zero deaths. No serious event terms are listed. Because there is no concurrent control group and the numerical outcome result is absent, the registry record cannot establish the magnitude or causal interpretation of change in competitive employment.