Efficacy and Safety Study of Seroquel SR in the Treatment of Major Depressive Disorder: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy and Safety Study of Seroquel SR in the Treatment of Major Depressive Disorder (NCT00388973), a randomized phase 3 study. The primary outcome is Change From Baseline in Montgomery-Asberg Depression Rating Scale (MADRS) Total Score to Week 9..

2. Clinical Question

The main comparison concerns average change in depressive symptoms rather than the proportion of patients meeting a response or remission threshold. The registry describes the MADRS total score as ranging from 0 to 60 units and defines change as the week 9 value minus the baseline value. It does not report a threshold for a clinically important difference, so the size of the observed group contrast cannot, from this record alone, be classified against such a threshold.

Other listed outcomes address health-related quality of life, anxiety symptoms, sleep quality, suicidal thoughts, somatic symptoms, medication satisfaction, and tolerability. These broaden the questions examined, but the primary comparison remains the week 9 MADRS change.

3. Trial Design

This was a phase III, multicentre, randomized, double-blind, parallel-group, placebo-controlled study sponsored by AstraZeneca. The registry record lists an enrollment of 338 and a completed status. The study started in 2006-09, with primary completion in 2007-12. The study description identifies the population as elderly patients with major depressive disorder and describes a 9-week treatment comparison.

The intervention is called quetiapine fumarate sustained release in the official study title and quetiapine XR in the arm results. The record notes that Seroquel SR and Seroquel XR refer to the same formulation, and that the SR designation was changed to XR after consultation with FDA. The comparator was placebo. The registry record does not report the allocation ratio, the randomization method, concealment details, or operational details of masking.

For the primary outcome, the reported population comprised randomized patients who took at least one dose of study medication and had at least one post-baseline assessment. For patients who did not complete the study, the record says the last observation was carried forward to week 9. The arm summaries report 164 patients for quetiapine XR and 171 for placebo; these are the counts associated with the posted primary outcome summaries, not a description of all randomized patients.

The registry lists secondary outcomes concerning quality of life, anxiety, sleep, suicidal thoughts, somatic symptoms, medication satisfaction, and adverse-event withdrawals. Numerical comparisons are posted for some, but not all, of these outcomes. The registry record does not report the original sample-size justification, a detailed statistical analysis plan, or the planned handling of multiplicity.

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: Screening for eligibility and wash-out of restricted medications. At least moderate depression symptoms assessed by the Hamilton Rating Scale for Depression

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All randomized patients who took at least one dose of study medication and had at least one post baseline assessment, with last observation carried forward to week 9 for patients who did not complete the study.

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 From Baseline in Montgomery-Asberg Depression Rating Scale (MADRS) Total Score to Week 9., measured over Baseline to Week 9.

The primary endpoint was change from baseline in MADRS total score to week 9. MADRS is a measure of depressive symptoms; the registry describes its total score as 0 to 60 units, with lower scores indicating less severe symptoms. Change was defined as the week 9 score minus the baseline score. Consequently, negative values indicate a decrease in score over the study period, and a more negative group mean indicates a larger average decrease.

The endpoint is a continuous measure, so the posted summary describes average change rather than classifying each participant as improved or not improved. Comparing mean changes between randomized groups provides an estimate of the average difference associated with assignment to the study treatments, subject to the population and missing-data approach used. The registry reports least-squares means and standard deviations for the arms, but does not report details of any model used to obtain those least-squares means.

A week 9 assessment provides a defined endpoint for this 9-week treatment study. The registry record does not report a threshold for interpreting a change as clinically important, nor does it provide a remission or response definition for the primary outcome. Thus, the mean contrast describes the size and direction of the observed group difference on the MADRS scale; it does not, by itself, describe the experience of every participant.

7. Results Posted in the Registry

• Quetiapine XR: mean -16.00 versus -9.00 on control; difference -7.00 (95% CI -8.71 to -5.29), standardized effect d = -0.88; z-test p = <0.001.

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.

Change From Baseline in Health-related Quality of Life, Enjoyment and Satisfaction (Q-LES-Q)

• 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:
  • Quetiapine XR: mean 17.00 versus 9.00 on control; difference 8.00 (95% CI 5.00 to 11.00), standardized effect d = 0.57; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Quetiapine XR than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Change From Baseline in Anxiety Symptoms Measured by Hamilton Anxiety 14 Item Scale (HAM-A)

• 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:
  • Quetiapine XR: mean -11.00 versus -5.00 on control; difference -6.00 (95% CI -7.51 to -4.49), standardized effect d = -0.85; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Quetiapine XR than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Change From Baseline in Sleep Quality as Measured by the Pittsburgh Sleep Quality Index

• 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:
  • Quetiapine XR: mean -6.00 versus -3.00 on control; difference -3.00 (95% CI -3.86 to -2.14), standardized effect d = -0.75; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Quetiapine XR than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The posted secondary comparisons point in directions broadly consistent with the primary result: the quality-of-life measure increased on average, while the anxiety and sleep measures showed decreases. Numerical comparisons are available for these outcomes, but the registry record lists additional secondary questions concerning medication satisfaction, suicidal thoughts, somatic symptoms, and adverse-event withdrawals without posting corresponding numerical comparisons in the secondary results. Their results are not reported in the registry record.

These outcomes add context because they cover aspects of health and symptoms beyond the primary MADRS score. They may help describe whether the pattern of changes extends across related measures, but they do not replace the primary endpoint or independently establish the primary finding. Differences among measures can arise because they assess different constructs, use different scales, or have different measurement properties.

The secondary comparisons have unadjusted p-values, and a multiplicity adjustment or testing hierarchy is not reported. When several outcomes are examined, some may appear to differ by chance even if there is no true difference for those outcomes. This makes unadjusted secondary results less conclusive than a prespecified primary result analyzed under a reported plan. The registry record does not report whether these secondary outcomes were intended as confirmatory tests or how their results were to be interpreted as a group.

Accordingly, the overall direction of the posted secondary estimates can be viewed as descriptive context, rather than as a collection of definitive independent conclusions. The absence of posted results for several listed outcomes and the lack of a reported multiplicity strategy further limit how comprehensively the secondary pattern can be assessed.

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

• Change From Baseline in Health-related Quality of Life, Enjoyment and Satisfaction (Q-LES-Q)
• Change From Baseline for Satisfaction With Medication From Quality of Life, Enjoyment, Satisfaction Questionaire (Q-LES-Q)
• Change From Baseline in Anxiety Symptoms Measured by Hamilton Anxiety 14 Item Scale (HAM-A)
• Change From Baseline in Sleep Quality as Measured by the Pittsburgh Sleep Quality Index
• Change From Baseline in Suicidal Thoughts as Measured by Montgomery-Asberg Depression Rating Scale (MADRS) Item 10
• Change From Baseline in Somatic Symptoms Cluster From the Hamilton Anxiety Scale (HAM-A)
• Tolerability as Measured by Adverse Event Withdrawals During Treatment

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous, and its posted arm summaries are least-squares means with standard deviations. A mean is a measure of the group’s average score change. A standard deviation describes how spread out individual observations are around that average; it is not the uncertainty in the mean itself. The arm means describe average within-arm change, while the mean difference compares those changes between the treatment groups.

What does the mean difference represent?

The posted mean difference for quetiapine XR is -7.0 units. The comparison is oriented as the quetiapine XR mean relative to the placebo mean, and the negative value indicates a more negative average change in the quetiapine XR arm. This is an unadjusted comparison based on the posted arm summaries, not a separately reported adjusted treatment effect. The record does not provide a detailed model specification for the least-squares means, so the precise adjustment used to produce them is not reported in the registry record.

The comparison also includes a standardized effect estimate of -0.875. A standardized mean difference expresses the group contrast in standard-deviation units rather than MADRS units. It can help describe the contrast on a scale that is less tied to a particular instrument, but it is not itself a clinical threshold. The standardized estimate depends on the variability used for standardization; it should not replace the scale-unit estimate when interpreting the MADRS result.

How should the p-value be read?

The reported p-value is unadjusted and is < 0.001. In general, a p-value is calculated under a null hypothesis and a statistical model. It describes the compatibility of the observed data with that null model; it is not the probability that treatment has no effect, and it does not tell how likely a result is to be replicated. A small p-value can accompany an estimate whose importance to patients is uncertain, while the magnitude and precision of the estimated contrast require separate consideration.

The record does not identify a multiplicity adjustment for testing several outcomes. An unadjusted p-value addresses the particular comparison without accounting for the wider set of analyses. If many outcomes or comparisons are examined, the chance of obtaining at least one small p-value by chance can increase. That general concern is one reason secondary findings without a reported multiplicity strategy warrant more cautious interpretation.

What does the confidence interval add?

A confidence interval gives a range of values compatible with the estimate under the method used. For the primary mean difference, the reported interval runs from -8.714 to -5.286. This range conveys uncertainty about the group-average contrast more directly than a p-value alone. The confidence level and construction details are not reported in the registry record, so they should not be inferred from the interval’s appearance.

Standard errors and confidence intervals depend on the amount of information and variability in the data. Greater variability or fewer observations generally makes an estimate less precise; less variability or more information generally makes it more precise. These are general statistical principles, not additional findings about this trial. The posted comparison notes that the standard deviation used for the recalculation is approximate. The recalculated comparison is therefore a simple, unadjusted assessment from the posted summary statistics rather than a substitute for a sponsor analysis. No discrepancy is flagged in the registry record.

How does the missing-data approach affect the endpoint?

The primary population included randomized patients who took at least one dose and had at least one post-baseline assessment. For those who did not complete the study, the registry says the last observation was carried forward to week 9. In general, last observation carried forward fills a missing endpoint with an earlier recorded value. This creates a complete endpoint value for the analysis but assumes that the earlier observation is an adequate stand-in for the unobserved week 9 result. If outcomes would have changed after the last assessment, that assumption may not hold.

The registry record does not report how many endpoint values were carried forward, why participants did not complete the study, or whether alternative missing-data analyses were conducted. It also does not report the original statistical analysis plan, details of the model for the primary outcome, or a formal sponsor analysis in the posted results. These gaps make it difficult to assess how sensitive the estimates are to analysis choices. The results should therefore be read as the posted summaries under the stated population and missing-data approach, not as evidence that all plausible approaches would produce the same estimate.

11. Confidence Intervals and Precision

The primary mean difference is -7.0 MADRS units, and its reported confidence interval extends from -8.714 to -5.286. The interval stays on the negative side of zero and is consistent with a larger average decrease in the quetiapine XR arm than in the placebo arm. Its endpoints give a range for the estimated group-average contrast under the interval method; they are not a range of individual participant outcomes.

A confidence interval is useful because it conveys both direction and precision. A narrower interval indicates less uncertainty about the estimated contrast than a wider interval, under the same method and assumptions. The registry record does not state the confidence level or construction method, so those details are not reported in the registry record. The interval should not be treated as a guarantee that the true contrast lies within its endpoints, or as a measure of clinical importance.

The unadjusted p-value is < 0.001, but it answers a different question from the interval. It describes the data’s compatibility with a null comparison under a model; it does not show whether the estimate is precise enough for a particular decision or large enough to matter clinically. The registry record does not report a clinical-importance threshold. The interval’s position and width should therefore be considered alongside the mean difference and the scale’s interpretation, rather than using the p-value alone.

The interval is associated with a simple unadjusted recalculation from the posted summary statistics, and the standard deviation used in that calculation is approximate. It should not be mistaken for a separately reported adjusted model estimate. The registry record does not flag a discrepancy between the posted results and the recalculation.

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 figures are participants per arm, not total events. The primary-outcome illustration uses the observed mean difference as a starting point and gives planning scenarios for detecting 100%, 75%, and 50% of that observed effect. For 100% of the observed effect, the figures are 21 participants per arm for 80% power and 28 participants per arm for 90% power. For 75% of the observed effect, they are 37 participants per arm for 80% power and 49 participants per arm for 90% power. For 50% of the observed effect, they are 83 participants per arm for 80% power and 110 participants per arm for 90% power.

The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is the stated fraction of the observed effect. The registry record does not report the trial’s own original sample-size assumptions or justification; these figures are planning illustrations based on the observed effect, not a reconstruction of the trial design.

In plain language, 80% power means that a study designed under those assumptions would have an 80% chance of detecting the specified effect using the stated test, if that effect were the true one. The 90% column represents a higher chance of detecting that effect under the same planning assumptions, and therefore requires a larger planned group size in the listed scenarios. Smaller effects are harder to distinguish from random variation and need more participants per arm. These figures are not observed power: they do not measure the probability that the completed trial’s result is correct.

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, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -7.000; pooled standard deviation σ = 8.000.
2. n = 2 × (1.96 + 0.842)² × 8.000² / -7.000² = 20.5, rounded up to 21 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
delta <- -7                      # observed difference in means
sigma <- 8                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^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 (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(388973)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 21 (80% power), 28 (90% power)
 75% of observed effect: n per arm = 37 (80% power), 49 (90% power)
 50% of observed effect: n per arm = 83 (80% power), 110 (90% power)
power.t.test: 21.5 
Simulated power at n = 21 per arm: 0.791 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-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. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary outcome and several secondary outcomes, but does not report a statistical analysis plan describing how the outcomes were prioritized or how multiplicity was handled. It is not reported in the registry record whether testing was organized in a hierarchy, whether any adjustment was planned, or whether the secondary findings were intended to be confirmatory. The posted p-values are unadjusted. When several outcomes are considered, unadjusted tests do not control the overall chance of a false-positive finding across the full set of tests.

The primary-outcome population was randomized patients who took at least one dose of study medication and had at least one post-baseline assessment. This is the population specified for the primary endpoint; it is not described in the record as an analysis of every randomized patient regardless of treatment exposure or assessment availability. The registry record does not report the number of randomized patients excluded from this endpoint population or the reasons for any exclusions.

For patients who did not complete the study, the primary endpoint used last observation carried forward to week 9. The record does not report the amount of missing data, when missingness occurred, or why assessments were unavailable. It also does not report sensitivity analyses using other missing-data assumptions. Since carrying an earlier observation forward may not reproduce the unobserved week 9 score, the lack of those details limits assessment of robustness.

The original trial sample-size justification, interim-analysis plan, detailed model specification, and sponsor analysis are not reported in the registry record. The registry record also does not report the confidence level or method used for the posted interval. These omissions do not alter the numerical summaries, but they restrict assessment of prespecification, model assumptions, and the influence of analysis decisions.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: depression (1.2%), depressive symptom (0.6%), polymyalgia rheumatica (0.6%), renal failure acute (0.6%), suicide attempt (0.6%).

The registry reports serious adverse events in the quetiapine XR and placebo groups, with 4 affected among 166 at risk for quetiapine XR and 2 affected among 172 at risk for placebo. These are counts of participants with serious adverse events and the corresponding groups at risk. The record does not provide enough detail in these summaries to interpret event timing, duration, or individual clinical circumstances. No comparative risk calculation is added.

The listed serious-event terms include Depression at 1.2%, Depressive Symptom at 0.6%, Polymyalgia Rheumatica at 0.6%, Renal Failure Acute at 0.6%, and Suicide Attempt at 0.6%. The record presents these as top serious-event terms; it does not identify a treatment group for each term in the posted list. They should not be read as estimates of comparative risk between groups.

Deaths are not reported in the registry record. These serious-event summaries describe reported counts, not a complete assessment of all possible harms or a basis for determining the cause of an event. The registry record also lists tolerability as measured by adverse-event withdrawals among the secondary outcomes, but does not post a numerical comparison for that outcome.

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

The posted primary result describes an average difference in MADRS change between quetiapine XR and placebo over the study’s baseline-to-week-9 period, for the stated primary-outcome population and missing-data approach. The mean contrast is negative, and the reported interval remains below zero. The unadjusted p-value is < 0.001. Together, these statistics describe the direction, estimated size, and statistical uncertainty of the posted group comparison.

They do not show that every participant improved, or that an individual’s change can be predicted from the group average. They also do not establish that the observed contrast meets a threshold of clinical importance, because the registry record does not report such a threshold. The average difference is not equivalent to a response rate, remission rate, or probability of benefit for a particular person.

The result applies to the trial population and the study period described in the registry record. It does not establish outcomes beyond week 9, and it should not automatically be extended to populations not described in the record. The primary analysis used last observation carried forward for patients who did not complete the study; missing-data details and sensitivity analyses are not reported. The result therefore depends in part on that stated approach.

The posted secondary findings provide descriptive context, but they are unadjusted and the record does not report a multiplicity strategy. Several listed secondary outcomes have no numerical results posted. Safety counts and event terms likewise require cautious reading: they are descriptive summaries and do not establish causation or comprehensively characterize risk. Overall, the record supports a statistical description of the posted comparison, not a complete account of clinical relevance, longer-term outcomes, or individual experience.

17. Why This Trial Matters Statistically

This study is statistically informative because it posts arm-level summaries and a direct mean comparison for a continuous primary outcome. The negative score changes are interpretable in relation to the scale direction, and the interval supplies information about the uncertainty around the estimated group contrast. Considering the means, the mean difference, the interval, and the unadjusted p-value together is more informative than treating any one statistic as a complete account.

The record also illustrates why the analysis population and missing-data method matter. The primary endpoint was based on patients with treatment exposure and a post-baseline assessment, and last observation carried forward was used for those who did not complete the study. These details are necessary for understanding what population the estimate describes and how unavailable week 9 values were handled. The extent of missing data is not reported, limiting evaluation of the method’s influence.

The secondary results and safety information show the value and limits of registry reporting. Several secondary comparisons are posted, but the record does not describe multiplicity handling and does not post numerical results for every listed secondary outcome. Serious-event counts and terms offer descriptive information, but cannot by themselves establish causality or comparative risk. The case underscores the statistical importance of distinguishing a posted estimate from its precision, clinical interpretation, and completeness of reporting.

18. 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 describes an elderly population with major depressive disorder but does not report a more detailed age range or other eligibility characteristics. That limits understanding of how narrowly the findings apply. The study’s primary endpoint is measured through week 9, and longer-term outcomes are not reported in the record. The analysis therefore does not describe persistence of the observed group difference beyond the stated period.

The primary analysis used last observation carried forward for patients who did not complete the study. The number of missing week 9 observations, reasons for non-completion, and sensitivity analyses are not reported in the registry record. Since this method relies on an earlier value standing in for a later one, the potential effect of the missing-data assumption cannot be evaluated from these summaries.

Other statistical details are also absent: the original sample-size justification, the detailed analysis model, the confidence interval method and level, and a multiplicity plan. The registry reports least-squares means but does not explain the model behind them. Secondary outcomes are listed more broadly than the numerical results posted, and safety summaries do not provide event-level timing or group attribution for the listed terms. These are reporting limitations; they do not establish that the underlying trial lacked such analyses or data, only that they are not reported in the registry record.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Efficacy and Safety Study of Seroquel SR in the Treatment of Major Depressive Disorder — NCT00388973.
• Registry record last updated 2010-04-01; status last verified 2010-03.
• Results first posted 2010-04-01.
• 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.

22. Record Summary

NCT00388973 is a completed, phase III, multicentre, randomized, double-blind, parallel-group, placebo-controlled study sponsored by AstraZeneca. It evaluated quetiapine fumarate sustained release, listed in the results as quetiapine XR, in elderly patients with major depressive disorder. The registry lists enrollment of 338 and a 9-week treatment period.

The primary endpoint was change in MADRS total score from baseline to week 9. The posted means were -16.0 for quetiapine XR and -9.0 for placebo, with a mean difference of -7.0 and a confidence interval from -8.714 to -5.286. The unadjusted p-value was < 0.001. The primary population required treatment exposure and at least one post-baseline assessment, with last observation carried forward for patients who did not complete the study.

Some secondary comparisons and serious adverse-event summaries are posted. The registry record does not report a multiplicity strategy, the original sample-size justification, detailed model methods, or numerical results for every listed secondary outcome.