Brief Group Psychoeducation for Schizophrenia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Brief Group Psychoeducation for Schizophrenia (NCT02911519), a randomized na study. The primary outcome is Number of Participants With Relapse.

2. Clinical Question

3. Trial Design

This was a randomized, parallel-group clinical controlled trial with single masking. The registry lists schizophrenia as the condition and describes the target population as adults with schizophrenia. A total enrollment of 176 is recorded: 90 participants in the brief group psychoeducation arm and 86 in the treatment-as-usual-only arm. The study is marked completed. Its phase is listed as not applicable.

Both groups received treatment as usual, described as psychiatric care normally received in the clinic. The intervention group additionally received brief group psychoeducation. The planned program consisted of five two-hour sessions, once a week. Each session was to be conducted by a clinical psychologist and a general practitioner trained in group management. The registry says the program was designed after a review of the literature and that its content and procedures would be written in a manual. It does not report how many participants attended each session or whether the intervention was delivered as planned.

The primary outcome was the number of participants with relapse during 12 months. Secondary outcomes listed include hospitalization, schizophrenia symptoms, treatment adherence, insight, quality of life measured by WHOQOL-BREF, family burden, and expressed emotions. Results are posted for hospitalization, insight, and expressed emotions; other listed secondary outcomes are not reported in the registry record as results in the posted outcome data.

The registry describes the study as randomized and single-masked, but does not report the randomization procedure, who was masked, allocation concealment, or the original sample-size justification. Further details about recruitment, sites, eligibility criteria, and analysis populations 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:

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 Number of Participants With Relapse, measured over 12 months.

The primary endpoint counts participants who experienced relapse during 12 months. The registry defines relapse as the reappearance of criteria for a psychotic episode in a patient who had no symptoms or only residual symptoms. Relapse could be identified by hospitalization, or by a Clinical Global Impression-Severity score greater than or equal to 3 together with an increase greater than 20% on the Scale for the Assessment of Positive Symptoms.

A participant count is a binary-outcome measure at the individual level: each participant is classified according to whether the endpoint occurred. This makes the endpoint directly interpretable as the number of participants meeting the relapse definition in each group. The group counts are 22 of 90 for brief group psychoeducation and 23 of 86 for treatment as usual alone.

Relapse is used as the primary endpoint because the study summary frames the intervention as being evaluated for relapse prevention. The endpoint definition combines a clinical event, hospitalization, with symptom-based criteria, allowing relapse to be recorded without requiring hospitalization in every case. The record does not report which route to the definition applied to each participant, how assessments were scheduled, or whether endpoint adjudication was independent of treatment assignment. These details are not reported in the registry record.

7. Results Posted in the Registry

• Brief Group Psychoeducation: 24.4% (22/90) versus 26.7% (23/86) on control; risk difference -2.3 percentage points (95% CI -15.2 to 10.6), risk ratio 0.91 (0.55–1.51); unadjusted two-proportion z-test p = 0.727.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Number of Patients With Hospitalization

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Brief Group Psychoeducation: 11.1% (10/90) versus 10.5% (9/86) on control; risk difference 0.6 percentage points (95% CI -8.5 to 9.8), risk ratio 1.06 (0.45–2.49); unadjusted two-proportion z-test p = 0.890.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Brief Group Psychoeducation and the control. The interval gives the range of effects that remain compatible with the data.

Insight

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Brief Group Psychoeducation: mean 14.90 versus 16.40 on control; difference -1.50 (95% CI -3.34 to 0.34), standardized effect d = -0.24; z-test p = 0.110.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Brief Group Psychoeducation and the control. The interval gives the range of effects that remain compatible with the data.

Expressed Emotions

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Brief Group Psychoeducation: mean 31.10 versus 30.80 on control; difference 0.30 (95% CI -1.49 to 2.09), standardized effect d = 0.05; z-test p = 0.742.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Brief Group Psychoeducation and the control. The interval gives the range of effects that remain compatible with the data.

The registry lists several secondary outcomes, while posted result data are available for hospitalization, insight, and expressed emotions. Taken together, the posted results do not show a precise separation between the assigned groups: the reported comparisons are uncertain and their intervals include values consistent with no difference. This overall pattern does not establish that the groups were identical, and it does not substitute for evidence on the other listed secondary outcomes for which results are not reported in the registry record.

These outcomes address different aspects of care and participant or family experience, and they use different measures. A result on one outcome cannot be assumed to predict a result on another. The primary endpoint remains the central comparison for the trial's stated relapse-prevention question; the secondary results provide additional context but do not overturn the uncertainty in the primary estimate.

Unadjusted secondary results carry less weight because the registry lists 8 outcome measures and 12 analyses, creating opportunities for chance findings when many comparisons are examined. The record does not report whether a multiplicity adjustment was used, how outcomes were prioritized beyond the named primary endpoint, or whether the posted analyses were prespecified. Without that information, secondary p-values should be treated as exploratory rather than as independent confirmations. The registry's outcome list also includes symptoms, adherence, quality of life, family burden, and expressed emotions, but results for those other listed measures are not reported in the posted outcome data.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Number of Patients With Hospitalization
• Symptoms of Schizophrenia
• Adherence to Treatment
• Insight
• Quality of Life Measure by WHOQOL-BREF
• Family Burden
• Expressed Emotions

9. Statistical Interpretation

10. Statistical Methods Explained

General explanation: A randomized comparison aims to make groups comparable at the point of assignment, so outcome differences can be interpreted as evidence about the assigned strategies, subject to the conduct and analysis of the trial. The registry records randomization and a parallel design but does not describe the randomization method or allocation concealment. The analysis details beyond the reported mixed models are not reported in the registry record.

What does a risk difference express?

The unadjusted recalculation uses a risk difference: the event risk in the intervention group minus the event risk in the comparator group. A value below zero indicates a lower observed event risk in the intervention group; a value above zero indicates a higher one. For relapse, the recalculated estimate is -0.023. Its confidence interval ranges from -0.152 to 0.106, so it includes no difference as well as possible effects in either direction. The unadjusted p-value is 0.727. A p-value measures how compatible the observed data are with a specified null model under its assumptions; it is not the probability that the null hypothesis is true.

How does the reported risk ratio differ?

The sponsor reports a mixed models analysis using a risk ratio. This compares the event risk in one group with the event risk in the other, rather than subtracting the two risks. The posted relapse estimate is 0.95, with a 95% confidence interval from 0.77 to 1.16 and p = 0.59. A ratio of 1 represents equal risks. The confidence interval includes that value, and also permits relative effects in either direction. The registry does not describe the model specification, covariates, handling of repeated measures, or other details needed to reconstruct the mixed models analysis.

What does a confidence interval convey?

General explanation: A confidence interval describes the range of estimates compatible with the observed data under the method's assumptions. It conveys statistical uncertainty, not a range in which the true effect is guaranteed to fall. The width depends on factors including the amount of information in the data and the variability of the outcome. For the primary outcome, the interval extends across no difference, a possible reduction, and a possible increase. That breadth is important: a point estimate alone would conceal how uncertain the comparison is.

Why are estimates called recalculated?

The risk-difference results are simple, unadjusted calculations from the posted group counts. They do not incorporate the sponsor's mixed models approach. For that reason, the recalculated estimate and the sponsor's risk ratio answer the comparison using different scales and potentially different assumptions. Neither should be substituted for the other. The sponsor's own analysis is the registry's reported analysis, while the unadjusted calculation helps interpret the raw group counts on an absolute-difference scale.

How should continuous secondary outcomes be read?

General explanation: A mean difference compares group averages on a measured scale. A positive or negative estimate indicates which group had the higher mean, according to the direction used for subtraction; it does not by itself indicate whether the difference is clinically important. Interpretation also depends on the scale's meaning, its measurement properties, and a threshold for meaningful change. The registry reports mean values and standard deviations for insight and expressed emotions, and reports sponsor mixed-model slopes for those outcomes. The meanings of those scales, meaningful-difference thresholds, and model specifications are not reported in the registry record.

Why can over-dispersion matter?

General explanation: Over-dispersion occurs when observed variation is greater than a statistical model expects. If a model assumes less variation than the data contain, uncertainty may be understated and inferential results can be too optimistic. The primary endpoint is a count of participants with an event, and the record does not report a dispersion estimate or a method addressing over-dispersion. No conclusion about whether over-dispersion occurred can be drawn from the registry record.

What is not specified?

The registry reports 12 analyses and 8 outcome measures, but does not describe the full statistical analysis plan, prespecified covariate adjustments, interim analyses, missing-data procedures, or analysis populations. It also does not report the assumptions used for the trial's original sample-size planning. The planning illustrations are based on the observed effects and stated assumptions; they do not reveal how the trial itself was designed. These distinctions matter because analysis choices affect interpretation, especially when multiple outcomes are evaluated or participant outcome data are incomplete.

11. Confidence Intervals and Precision

Precision concerns how narrowly the data constrain an effect estimate. For relapse, the recalculated risk difference is -0.023, with a 95% confidence interval from -0.152 to 0.106. The interval contains zero, so the posted data are compatible with no absolute difference. It also extends to estimates favoring either group. The point estimate alone therefore gives an incomplete account: the interval indicates that the direction and size of the underlying difference remain uncertain.

The sponsor's mixed models risk ratio for relapse is 0.95, with a 95% confidence interval from 0.77 to 1.16. The interval includes 1, the value representing equal relative risks. It allows for a lower relative risk as well as a higher one. The sponsor's estimate is on a relative scale, whereas the recalculated risk difference is on an absolute scale; their intervals should be interpreted according to their respective measures.

General explanation: A 95% confidence interval is generated by a method that, under its assumptions, would cover the true parameter in 95% of repeated samples. It does not mean there is a 95% probability that the fixed true effect lies within this particular interval. Wider intervals indicate less precision, while narrower intervals indicate more precision, all else equal. Precision does not establish clinical importance: a narrow interval can still include effects too small to matter, and a broad interval can leave important effects unresolved.

The recorded group sizes are 90 and 86, and the total enrollment is 176. The registry's intervals should be read in light of the information available from this trial, not as proof that effects are absent. Confidence intervals for the posted secondary outcomes also cross their respective null values. Their precision and interpretation depend on the outcome scale and analysis method; clinical thresholds for interpreting those measures are not reported in the registry record.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They use the observed effect as the reference and consider detecting 100%, 75%, or 50% of that observed effect. All outcomes in these illustrations are participant counts or continuous outcomes, so the figures are participants per arm, not total events. The trial's original sample-size assumptions and justification are not reported in the registry record.

The 80% power column indicates the number of participants per arm that the stated planning calculation estimates would be needed to have an 80% chance of detecting the specified effect under its assumptions, if that effect were real. The 90% power column gives the corresponding planning figure for a higher chance of detecting that effect. These are design illustrations, not guarantees about a future study's result.

Smaller effects require more participants to distinguish them from random variation with the same chosen power and significance level. The displayed scenarios therefore increase the assumed sample size as the effect to detect is reduced from the full observed effect to a smaller fraction. The estimates depend on the observed effect, which is uncertain, and on the stated calculation assumptions; a different true effect or design could require different sample sizes.

These figures are planning illustrations, not observed power. They do not measure the probability that the completed trial detected an effect, nor do they explain why the actual trial enrolled 176 participants. The record does not report the assumptions behind that original enrollment target.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.267; treatment proportion p₁ = 0.244; average p̄ = 0.256.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6171 = 1.2096.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6169 = 0.5192.
4. n = (1.2096 + 0.5192)² / (-0.0230)² = 5,651.2, rounded up to 5,652 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.267441860465116                          # control proportion
p1 <- 0.244444444444444                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(2911519)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 5,652 (80% power), 7,565 (90% power)
 75% of observed effect: n per arm = 10,122 (80% power), 13,549 (90% power)
 50% of observed effect: n per arm = 22,938 (80% power), 30,707 (90% power)
power.prop.test: 5651.2 
Simulated power at n = 5,652 per arm: 0.801 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

For relapse, the registry's sponsor analysis is a mixed models analysis reporting a risk ratio of 0.95, with a 95% confidence interval from 0.77 to 1.16 and p = 0.59. The separate recalculation from the posted participant counts is an unadjusted risk difference of -0.023, with a 95% confidence interval from -0.152 to 0.106 and p = 0.727. These estimates use different effect measures and analytical approaches, so the numerical values are not directly interchangeable.

The unadjusted calculation is useful as a transparent comparison of the posted counts, while the sponsor's result is the registry's reported model-based analysis. The registry does not provide enough model detail to reproduce that analysis or determine precisely how it accounts for the data. The reported estimates both have confidence intervals that include their respective null values, and both indicate uncertainty about the size and direction of the comparison. There is no discrepancy flag between the recalculation and reported analysis. The sponsor's own analysis takes precedence as the trial's reported analysis; the recalculation is supplementary and should not be presented as a replacement.

15. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when several outcomes, time points, subgroups, or analyses are tested. Even when no underlying group differences exist, examining many comparisons increases the chance that at least one result appears unusual by chance. The registry lists 8 outcome measures and 12 analyses, identifies relapse as the primary outcome, and provides secondary outcome listings. It does not report whether the analysis plan prespecified a hierarchy for secondary outcomes or applied a statistical adjustment for multiple testing. Accordingly, secondary findings should be interpreted cautiously, and an isolated p-value should not be treated as definitive evidence.

The record also does not report how missing outcome data were handled, how many participants lacked each outcome, or whether analyses followed an intention-to-treat approach. It does not describe analysis populations, exclusions after randomization, or sensitivity analyses examining the effect of missing data. These omissions matter because results can be affected if outcome availability differs between groups or is related to participants' outcomes.

Additional details that would help assess the findings—including the full statistical analysis plan, interim analyses, model specification, and procedures for handling protocol deviations—are not reported in the registry record. No conclusion should be drawn that these procedures were or were not used. Their absence from the registry information limits the ability to assess prespecification, robustness, and the role of analytical choices.

16. 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 reports zero serious adverse events in the brief group psychoeducation group, among 90 participants at risk, and zero in the treatment-as-usual-only group, among 86 participants at risk. It also records zero other adverse events in each group and zero deaths in either group. No serious adverse-event terms are listed.

These figures describe the events recorded in the registry. Zero recorded events should not be read as proof that no harms occurred: the record does not describe the adverse-event collection method, observation period, reporting thresholds, or completeness of surveillance. It also does not provide event-level details or a comparison of event types beyond the counts. The figures therefore offer a limited account of reported safety information and cannot establish the absence of risk or characterize all possible harms.

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

The posted primary data show 22 participants with relapse among 90 in the brief group psychoeducation arm and 23 among 86 in the treatment-as-usual-only arm. The sponsor's mixed models analysis reports a risk ratio of 0.95, with a 95% confidence interval from 0.77 to 1.16 and p = 0.59. The unadjusted recalculation reports a risk difference of -0.023, with a 95% confidence interval from -0.152 to 0.106 and p = 0.727. These results do not provide a precise estimate of the difference between groups.

The confidence intervals include the null values for their respective measures and allow for effects in either direction. This means the trial does not establish a clear difference in relapse under the reported analyses. It also does not establish equivalence or prove that no meaningful difference exists. A non-significant result can reflect an effect close to zero, limited precision, or both; the registry record does not resolve those possibilities.

The result applies to the participants, intervention, comparator, outcome definition, and follow-up recorded for this trial. The registry does not provide detailed participant characteristics, implementation information, or enough analysis detail to determine how broadly the estimates may apply. The findings should not be interpreted as medical advice or as a treatment recommendation. They describe the reported comparison and its statistical uncertainty, not a universal conclusion about psychoeducation or usual psychiatric care.

18. Why This Trial Matters Statistically

This trial illustrates why a point estimate and its uncertainty need to be considered together. The raw relapse counts are close, and the primary estimates point toward a small difference on their respective scales, but the confidence intervals are broad enough to include effects in either direction. Reporting only the point estimate or only whether a p-value crosses a threshold would omit important information about precision.

It also shows how analyses can express the same comparison in distinct ways. The sponsor reports a mixed-model risk ratio, while a simple recalculation from the posted counts gives an unadjusted risk difference. Relative and absolute measures answer related but different questions, and neither should be confused with the other. The sponsor's model is the reported trial analysis; the simpler recalculation helps make the observed counts interpretable without reproducing that model.

Finally, the record places the primary outcome alongside multiple secondary measures and analyses. That breadth can be useful for describing different aspects of an intervention, but it makes prespecification and multiplicity procedures important for judging secondary findings. Those details, along with missing-data procedures and the original sample-size justification, are not reported in the registry record. The trial is therefore a useful example of both the value of quantitative reporting and the limits imposed when key design and analysis details are unavailable.

19. 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 limitations arise from details not reported in the registry record. The randomization procedure, allocation concealment, and identity of the person or personnel masked are not specified. Participant characteristics, eligibility criteria, recruitment setting details, and adherence to the planned psychoeducation sessions are also not described in the posted information. These omissions make it harder to judge group comparability, intervention delivery, and how well the results may apply beyond the enrolled participants.

The relapse definition combines hospitalization with symptom criteria, but the registry does not report how events were assessed, which criterion triggered each event, or whether outcome assessment was independent of group assignment. The time-to-event pattern and timing of relapse are not reported; the primary outcome is posted as a participant count over 12 months.

The registry does not report the original sample-size justification, full analysis plan, missing-data handling, analysis populations, model details, or multiplicity procedures. These are important for evaluating the precision and robustness of the estimates. The posted secondary results cover only some of the outcomes listed in the registry, and the unadjusted secondary analyses should be treated cautiously. Finally, zero recorded adverse events cannot establish complete safety surveillance. These limitations qualify interpretation of the record without implying that unreported procedures were absent from the conduct of the study.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Brief Group Psychoeducation for Schizophrenia — NCT02911519.
• Registry record last updated 2020-05-06; status last verified 2020-04.
• Results first posted 2020-05-06.
• 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.

23. Record Summary

The registry describes a completed randomized, single-masked, parallel-group trial of brief group psychoeducation added to treatment as usual versus treatment as usual alone for adults with schizophrenia. Enrollment was 176. The primary endpoint was the number of participants with relapse over 12 months, defined using hospitalization or specified symptom criteria. Relapse was recorded for 22 of 90 participants assigned to psychoeducation and 23 of 86 assigned to usual care alone.

The sponsor's mixed models analysis reported a risk ratio of 0.95, with a 95% confidence interval from 0.77 to 1.16 and p = 0.59. An unadjusted recalculation gave a risk difference of -0.023, with a 95% confidence interval from -0.152 to 0.106 and p = 0.727. Both estimates are uncertain and do not establish a clear group difference. Secondary results are posted for hospitalization, insight, and expressed emotions; further listed outcomes and important design and analysis details are not reported in the registry record.