A Brief Cognitive Task Intervention for NHS Staff Affected by COVID-19 Trauma (GAINS-2 Study): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Brief Cognitive Task Intervention for NHS Staff Affected by COVID-19 Trauma (GAINS-2 Study) (NCT05616676), a randomized na study. The primary outcome is Number of Intrusive Memories of Traumatic Event(s).

2. Clinical Question

The clinical question is whether access to either digital task is associated with a different number of recorded intrusive memories than routine care in this trial population. The study also planned to examine other symptoms and aspects of functioning, including PTSD, sleep, anxiety, depression, work functioning, general functioning and quality of life. Feasibility, acceptability and implementation were additional areas of interest. Those broader aims do not establish that results for those outcomes are available in the registry record.

3. Trial Design

GAINS-2 was a randomized, parallel-group trial with single masking. It was marked completed in the registry record, with enrollment of 122. The recorded start date is 2022-12-08 and the primary completion date is 2023-10-30. The sponsor is P1vital Products Limited. The study is identified as not applicable for phase.

Three groups were described: a brief digital imagery-competing task, a brief digital music-listening task, and treatment as usual. Each assigned approach was described over 24 weeks. For both digital tasks, researcher support was optional during the first 4 weeks. Treatment as usual was described as routine care participants would otherwise receive for intrusive memories of traumatic events. The record does not report details of how randomization was generated or concealed, or what the single masking arrangement involved.

The registry describes an intended recruitment of approximately 150 NHS staff, while the recorded enrollment is 122. These are different kinds of figures: the former is an intended recruitment description and the latter is the recorded enrollment. The recruitment routes named in the study description were the Intensive Care Society, social media and direct advertising by NHS Trusts.

The primary outcome was the number of intrusive memories, measured at the run-in or screening week and Week 4. The study description also lists secondary outcomes such as the PTSD Checklist for DSM-5, Sleep Condition Indicator, brief anxiety and depression measures, work engagement and burnout scores, and sickness absence. The registry record lists 29 outcome measures, but does not report numerical results for them in the material available in the record.

Although the primary outcome and time points are identified, the record does not reduce them to one comparison. It does not report a single primary-outcome estimate, its uncertainty, or a test comparing the groups. That absence limits what can be concluded about the trial’s comparative findings.

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: Prior to randomisation, nine participants were excluded for having fewer than three IMs in the baseline IM diary, eight were lost to follow-up, and six withdrew prior to randomisation. These participants are detailed in the 'Run-in week only (non-randomised)' arm in the Participant Flow.

Run-In/Screening Week

Reasons for not completing this period:

Baseline Questionnaires/Randomisation

Reasons for not completing this period:

Receive Treatment/TAU Equivalent (Day 0)

Reasons for not completing this period:

Week 4

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All analyses were completed on an intention-to-treat basis as a between-group comparison.

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: All participants randomised to an experimental condition (groups combined, n=99)

6. Primary Endpoint

The registry lists the primary outcome as Number of Intrusive Memories of Traumatic Event(s), measured over Run-in/screening week, Week 4 (all arms).

The primary endpoint was the number of intrusive memories of traumatic events. Participants recorded these in a brief daily online diary for 7 days. The registry specifies the run-in or screening week and Week 4 as the measurement times, with the stated timeframe applying to all arms.

Counting intrusive memories provides a direct measure of the experience targeted by the study. A diary can capture repeated experiences over a defined period rather than relying only on a broad retrospective impression. In general, repeated recording can make an outcome more closely tied to the time window being studied, although it still depends on participants completing the diary and reporting experiences as intended. These are general measurement considerations, not reported findings about diary completion in this trial.

The outcome was specified as a median with an inter-quartile range. In general, the median describes the middle of an ordered set of observations, while the inter-quartile range describes the spread of the central portion of those observations. These summaries can be useful when a count outcome is unevenly distributed or includes values that are far from the middle. The registry record does not report the actual medians or inter-quartile ranges.

The recorded timeframe includes both a run-in or screening measurement and a Week 4 measurement. The record does not state a single numerical contrast that combines or selects these times, nor does it give a numerical primary-endpoint result for any group. The primary outcome therefore identifies what the trial intended to measure, but the registry record does not show how the groups compared on that endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a randomized, single-masked, parallel-group design and states that analyses were completed on an intention-to-treat basis as a between-group comparison. These labels describe broad features of the design and analysis, but they do not specify the complete statistical plan. The registry record does not report the method used to generate the random sequence, allocation concealment, or the details of masking.

What does a randomized comparison mean?

In general, random allocation is intended to make assignment to groups independent of participants’ characteristics, on average. This supports a fair comparison of assigned approaches, although chance differences between groups can still occur. The registry’s randomized designation does not reveal whether groups were balanced on any particular characteristic. No baseline comparison results are reported in the registry record.

A parallel-group design means participants are assigned to a group and the groups are compared over the study. Here, the listed groups were the two digital tasks and treatment as usual. The record describes access to the assigned approach over 24 weeks, while the primary outcome timeframe names the run-in or screening week and Week 4. The record does not explain how the primary outcome’s time points were combined in the analysis.

Why report a median and inter-quartile range?

The primary outcome is a count of intrusive memories, and the registry specifies a median and inter-quartile range. In general, the median is the central value after observations are ordered. The inter-quartile range describes the spread of the middle portion of the observations. These summaries can describe count data without requiring the distribution to be symmetric. They do not, on their own, quantify the uncertainty in a group comparison.

In general, count outcomes may have many observations near the lower end and fewer much larger values. If the variation is greater than a simple model expects, that is called over-dispersion. Over-dispersion matters because a model that assumes less variation than is present can produce uncertainty estimates that are too small. This is a general consideration for count outcomes; the registry record does not report a model, distributional assessment, or over-dispersion analysis for this trial.

What does intention-to-treat indicate?

In general, an intention-to-treat analysis compares participants according to their randomized assignment, rather than regrouping them according to the intervention they actually received or completed. This preserves the randomized comparison and reflects assignment to the study approaches. The registry states that analyses used an intention-to-treat basis, but does not report how participants with missing diary entries or other incomplete outcome data were handled.

The phrase “between-group comparison” indicates that the groups were to be compared, but it does not identify the exact statistical test or model. The registry record does not report whether the primary comparison adjusted for baseline values, accounted for repeated observations, used a particular link function, or included any other covariates. It also does not give an effect estimate, confidence interval, or p-value for the primary outcome.

What does a confidence interval contribute?

In general, a confidence interval describes the uncertainty around an estimated effect under a specified statistical method. It helps distinguish a relatively precise estimate from one that is compatible with a broad range of values. A confidence interval is not a guarantee that the true effect lies within its limits, and it does not replace consideration of the estimate’s meaning. No confidence interval for the primary comparison is reported in the registry record.

A p-value, in general, describes how surprising data at least as extreme as those observed would be under a specified null model. It does not give the probability that a treatment is effective, nor does it describe the size or practical importance of an effect. The registry record does not report a primary-outcome p-value. Without the effect estimate and its uncertainty, the groups’ comparative result cannot be evaluated from this record.

What can be inferred from the stated sample size?

The registry records enrollment of 122. Enrollment alone does not indicate how many participants contributed observations to each endpoint, whether diary completion was complete, or how precise an estimated effect would be. The record does not report a sample-size justification or the assumptions used for the trial’s design. Any planning illustration based on an observed effect is not the trial’s original design justification and is not observed power. It should be interpreted as a hypothetical planning calculation, not as evidence that the study had a particular probability of detecting an effect.

The record lists a primary outcome with more than one time point and does not reduce it to one comparison. That makes it especially important to know which contrast and time point were prespecified as the principal test. The choice can affect interpretation, but the relevant statistical plan is not reported in the registry record. No particular approach should be inferred from the outcome description alone.

The registry lists multiple secondary and additional outcomes. In general, testing many outcomes can increase the chance of obtaining at least one apparently notable result by chance. Methods such as a prespecified testing hierarchy or adjustment can address aspects of multiplicity, but no multiplicity strategy is reported in the registry record. The record also does not report a statistical analysis plan or detailed outcome-specific analysis methods. Consequently, the design labels and outcome definitions give useful context, while leaving major analytic choices and all comparative results unspecified.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 29 outcome measures, including the primary intrusive-memory outcome, measures of PTSD symptoms, sleep, anxiety and depression, work engagement and burnout, and sickness absence. A study examining multiple outcomes and time points must distinguish the primary question from secondary or exploratory questions. In general, repeated testing can make apparently notable findings more likely to arise by chance. A prespecified testing hierarchy or an adjustment for multiple comparisons can help address this issue, but the registry record does not report a multiplicity strategy.

The primary outcome is identified, but its timeframe includes the run-in or screening week and Week 4. The registry does not specify a single primary comparison across those time points. The record’s note that the outcome has several categories or time points and is not reduced to one comparison means there is no single primary result presented for interpretation.

The record states that analyses were completed on an intention-to-treat basis. It does not report how missing diary days, missing outcome measures, withdrawals, or other incomplete data were handled. It also does not report the amount or pattern of missing data for the primary outcome. In general, missingness can affect a comparison if the likelihood of an observation being unavailable is related to participants’ outcomes or group assignment.

There is no reported account of imputation, complete-case analysis, sensitivity analysis, or assumptions about missingness. These methods and assumptions are not reported in the registry record. The intention-to-treat label is therefore relevant but insufficient to establish how incomplete observations were incorporated. The registry also reports 0 analyses, so the record does not provide outcome-specific estimates or analysis results that could clarify these questions.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pneumonia (2.6%), post-operative infection (hysteroscopy) (2.6%), surgery for cervical myelopathy (2.6%), endometriosis (2.5%), kidney infection (2.5%).

The registry lists serious and other adverse-event counts separately for the study groups. For the brief digital music-listening task, the counts are 3 serious and 6 other adverse events. For the brief digital imagery-competing task, they are 3 serious and 2 other adverse events. For treatment as usual, the counts are 0 serious and 0 other adverse events. The run-in week group, identified as pre-randomized and non-randomized, has 0 serious and 3 other adverse events. The record lists 0 deaths in each group.

These are descriptive registry counts, not evidence that an event was caused by an intervention. The record does not report event narratives, timing relative to intervention exposure, investigator judgments about relatedness, or a comparative safety analysis. The run-in group is not one of the randomized arms and should not be treated as a randomized comparator.

In general, adverse-event counts are most informative when considered alongside the number of people at risk, the event definitions, follow-up completeness and the method used to assess relatedness. The registry includes at-risk figures, but the counts alone do not establish comparative risk or causation. They also do not show whether a person experienced more than one event. The registry record does not provide further information to resolve these points, so the figures should be read as reported counts rather than as a conclusion about safety.

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

The registry record establishes that GAINS-2 was a randomized comparison of two brief digital tasks with treatment as usual among NHS staff experiencing intrusive memories of work-related traumatic events during the COVID-19 pandemic. It identifies the primary outcome as diary-recorded intrusive-memory counts and gives the intended measurement times. It also records enrollment of 122 and reports descriptive adverse-event counts.

It does not report the primary endpoint values, a between-group effect estimate, a confidence interval, or a p-value. Therefore, the posted registry information does not show whether the groups differed in intrusive-memory counts, how large any difference was, or how precisely it was estimated. It also does not support a conclusion about secondary outcomes such as PTSD symptoms, sleep, anxiety, depression, work functioning or sickness absence, because their numerical results are not reported in the registry record.

Absence of a result in the registry record is not evidence that there was no effect or that the groups had identical outcomes. It means that the comparison cannot be evaluated from the reported information. Likewise, the existence of a randomized design does not by itself demonstrate a benefit or harm; interpretation requires the outcome data and the corresponding statistical analysis.

The safety counts are also limited in meaning. They describe adverse-event counts recorded for the named groups, but do not establish that an intervention caused an event or show a comparative safety effect. The run-in group is described as pre-randomized and non-randomized and is not an additional randomized treatment arm.

In general, a clinical trial result is best interpreted using the estimated effect, its uncertainty, the outcome definition, the analysis population and the completeness of follow-up. The registry record identifies some of these design features, including the intention-to-treat basis, but does not provide the primary comparison or details of missing-data handling. Conclusions about comparative effectiveness or precision would therefore go beyond what the registry record reports.

13. Why This Trial Matters Statistically

This trial poses a focused statistical question about a count outcome that is directly tied to the experience the intervention aims to address: intrusive memories recorded by daily diary. The design compares two distinct digital tasks with treatment as usual, allowing the clinical question to distinguish between the two task approaches rather than treating them as one intervention. The registry also identifies outcomes extending beyond intrusive memories to symptoms, work-related measures and sickness absence.

The trial is statistically informative as a design, but a design is not a result. Randomization supports a planned comparison, and the stated intention-to-treat basis indicates an intention to preserve participants’ assigned groups in analysis. However, the registry record reports 0 analyses and no primary-outcome estimates. This makes the distinction between study registration and results especially important: readers can understand what was planned and what was measured without being able to judge the comparative finding.

The endpoint’s specified median and inter-quartile range also highlight a general issue in clinical trials: the choice of summary should match the outcome’s distribution and the question being asked. A descriptive summary of each group and an estimate of the between-group contrast answer related but different questions. Without the contrast and its uncertainty, group-level patterns cannot be translated into a precise comparative conclusion.

The record further illustrates why analysis details matter when outcomes involve multiple time points and numerous secondary measures. Clear specification of the primary contrast, multiplicity approach and missing-data handling helps readers distinguish planned inference from exploratory findings. Those details are not reported in the registry record, so the available information supports a careful account of design, not a claim about an observed intervention effect.

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 central limitation of the available registry information is the absence of numerical results for the primary outcome. The record identifies the number of intrusive memories as the primary endpoint and specifies the run-in or screening week and Week 4, but it does not give group summaries or a comparative estimate. It also reports 0 analyses. Consequently, the statistical result and its precision cannot be assessed.

The endpoint is described at multiple time points, and the registry record does not reduce it to one comparison. It does not specify which time point or contrast should serve as the principal interpretation. The record also does not report the analysis model, any adjustment for baseline outcome values, how repeated observations were handled, or a statistical analysis plan.

The registry states that analyses were on an intention-to-treat basis, but does not describe missing-data methods or report the extent of missing diary observations. This limits assessment of whether incomplete measurement could affect the comparison. The record does not give outcome-specific participant counts or completion information for the primary endpoint.

The study description states an intended recruitment of approximately 150 NHS staff, while recorded enrollment is 122. The registry does not report a sample-size justification or the rationale for the enrollment target. It also does not provide a detailed account of randomization procedures, allocation concealment, or the single-masking arrangement. These details are not reported in the registry record and should not be inferred.

The safety counts are descriptive and do not include a reported causal assessment or detailed event-level context. In addition, the run-in group is labeled pre-randomized and non-randomized, so it should not be interpreted as a randomized comparator. Together, these limitations mean the registry record can describe the trial structure and recorded counts, but cannot establish comparative outcome effects or explain their clinical importance.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Brief Cognitive Task Intervention for NHS Staff Affected by COVID-19 Trauma (GAINS-2 Study) — NCT05616676.
• Registry record last updated 2026-05-27; status last verified 2026-04.
• Results first posted 2026-05-27.
• 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

GAINS-2, titled “A Brief Cognitive Task Intervention for NHS Staff Affected by COVID-19 Trauma,” was a completed randomized, single-masked, parallel-group trial sponsored by P1vital Products Limited. It recorded enrollment of 122 and compared a brief digital imagery-competing task, a brief digital music-listening task, and treatment as usual. The interventions were described over 24 weeks.

The primary outcome was the number of intrusive memories recorded in a brief daily online diary for 7 days, with the registry specifying the run-in or screening week and Week 4. The stated analysis population was intention-to-treat, with a between-group comparison. The registry lists 29 outcome measures and 0 analyses. It does not report the primary outcome values, a comparative effect estimate, or uncertainty around that estimate.

Safety counts are reported for serious and other adverse events, with 0 deaths listed in each group. These counts are descriptive and do not establish causation. The registry record therefore describes the trial design, outcomes and safety counts, but does not provide the comparative results needed to assess the primary clinical question.