A Double Blind Clinical Trial of DCS for Food Anxiety: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Double Blind Clinical Trial of DCS for Food Anxiety (NCT01996644), a randomized na study. The primary outcome is Anxiety as Measured by the Subjective Units of Distress (Ranging From 1 to 100)..

2. Clinical Question

The study is described as a pilot investigating whether DCS augments exposure therapy for food anxiety. Its stated expectations were that exposure therapy would reduce anxiety, that anxiety reduction would be greater with DCS than with placebo, and that BMI would increase more in the DCS condition. These are study expectations, not results established by the primary anxiety outcome.

The primary endpoint is anxiety measured with the Subjective Units of Distress scale, ranging from 1 to 100. The scale description defines 1 as no anxiety and 100 as the most anxiety ever experienced. The endpoint description says measurements at four sessions were combined in a repeated-measures ANOVA to give total anxiety decrease across condition. The posted results report arm means and a mean difference, but the registry record does not report the session-by-session scores or a separate BMI result.

3. Trial Design

The registry identifies this as a randomized, parallel-group trial with triple masking. Its title describes it as double blind, while the masking field records triple masking; the record does not explain the difference between those descriptions. The study is marked completed. Enrollment is 47, and the phase is recorded as NA.

The trial is described as a pilot study of cycloserine, abbreviated DCS, as a learning enhancement medication used alongside exposure therapy for food anxiety. The intervention labels are not consistent across the record. The intervention list names Placebo vs Setraline and Setraline, while the arm description for Setraline says 250 mg DCS (setraline) versus placebo plus exposure. The other arm is described as placebo plus exposure. The registry record does not clarify whether Setraline is an intended drug name or a label attached to DCS.

The reported outcome concerns anxiety measured twice a week for two weeks, with four sessions combined as described in the endpoint text. The record lists 20 participants in the Setraline arm and 16 in the placebo arm for this outcome. The study start is recorded as 2013-02 and primary completion as 2014-02. These dates describe the registry record; they do not add detail about recruitment, follow-up beyond the stated outcome timeframe, or analysis timing.

The registry record does not report the original sample-size justification, eligibility criteria, allocation ratio, or detailed masking procedures. It also does not describe how the treatment and exposure sessions were delivered. The stated study expectations include anxiety and BMI, but no secondary outcomes are posted in the results summarized for this trial. The design supports describing the recorded comparison, while the limited information does not permit a fuller reconstruction of the protocol.

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: 47 participants were enrolled in the study, but only 36 were randomized and given any medication or placebo (i.e., participants completed the assessment portion of the study but did not move to the active experimental portion of the study).

Overall 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 Anxiety as Measured by the Subjective Units of Distress (Ranging From 1 to 100)., measured over Twice a week for two weeks.

The primary endpoint is anxiety measured with the Subjective Units of Distress scale, which ranges from 1 to 100. The record defines the scale endpoints as 1 for no anxiety and 100 for the most anxiety ever experienced. Anxiety was measured at four sessions, twice a week for two weeks, and the description says the repeated measurements were combined in a repeated-measures ANOVA to give total anxiety decrease across condition.

An anxiety rating gives a numerical measure of the experience targeted by the exposure therapy described in the study. Using the same scale in both arms allows the recorded anxiety scores to be compared. The repeated-measures description indicates that the outcome concerns observations across sessions rather than a single measurement at one session. In general, repeated measurements can describe a pattern over time while accounting for the fact that measurements from the same participant are related. The registry record does not provide the session-level values or further details of the model used.

The posted results identify the outcome as a mean on a continuous measure and give a mean and standard deviation for each arm. The outcome title calls it anxiety as measured by the scale, while the description refers to total anxiety decrease across condition. The record does not specify the calculation used to turn session scores into that total or whether the arm means are baseline-adjusted. BMI is mentioned as a study expectation, but a BMI result is not reported in the registry record.

7. Results Posted in the Registry

• Setraline: mean 52.40 versus 58.98 on control; difference -6.59 (95% CI -10.44 to -2.73), standardized effect d = -1.14; z-test p = <0.001.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a continuous anxiety measure, summarized as a mean and standard deviation in each arm. The comparison is reported as a mean difference. These statistics describe the location and spread of scores in the groups and the difference between their reported means. The registry record also describes the four anxiety sessions as combined in a repeated-measures ANOVA, but does not provide enough detail to reproduce or assess that model fully.

What does a mean difference represent?

A mean difference expresses the contrast between two group averages in the original outcome units. Here, the posted contrast is -6.588 units, with the comparison direction defined by the Setraline and placebo labels. A negative value indicates that the first arm's reported mean is lower than the comparator's mean. The scale defines lower values as less anxiety. This is a group-level summary: it does not show how every participant's score changed, and it does not describe the distribution of individual responses.

The standard deviations are 5.493 for Setraline and 6.141 for placebo. In general, a standard deviation describes how spread out measurements are around a group mean. It is not the same as the uncertainty in the mean or the uncertainty in the difference between means. Those quantities also depend on the number of observations and the analysis used.

Why use repeated measurements?

The outcome description says anxiety was assessed at four sessions, twice a week for two weeks, and combined in a repeated-measures ANOVA. In general, repeated-measures methods are used when the same participants contribute measurements at multiple times. Measurements from one person are usually related, and a suitable analysis accounts for that relationship rather than treating every observation as independent. Such methods can examine patterns across time or combine repeated measurements, depending on the model.

The record does not report the exact repeated-measures model, the covariance structure, any assumptions checks, or the specific way session scores were combined. It also does not report separate estimates for each session. The posted arm means and mean difference should therefore be read as the registry's summary results, not as a reconstruction of the repeated-measures analysis.

What does the confidence interval add?

A confidence interval describes uncertainty around an estimated effect. In general, a confidence interval gives a range of values compatible with the data under the analysis assumptions and method used. The interval for this comparison runs from -10.44 to -2.734. Its placement below zero indicates that the reported range does not include no difference, under that method. It does not mean that every value in the interval is equally likely, and it does not account for sources of uncertainty that the analysis did not include.

How should the p-value be read?

The reported p-value is p < 0.001 and is identified as unadjusted. In general, a p-value describes how compatible the observed data are with a specified null model, assuming the model and test assumptions hold. It is not the probability that the null hypothesis is true, nor does it measure the size or importance of an effect. An unadjusted result does not account for multiplicity unless an adjustment is separately reported. The registry record does not give details of the test producing this value or any multiplicity plan.

The posted comparison combines a point estimate, interval, and p-value, which answer different questions: the estimated direction and magnitude, the uncertainty around that estimate, and compatibility with a null model under a test. None by itself establishes causality. Randomization is a design feature, but evaluation also depends on conduct, outcome availability, analysis choices, and the assumptions underlying the analysis; several of those details are not reported in the registry record.

Why can over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a statistical model expects. When a model assumes less variability than is present, uncertainty estimates can be too small and tests can appear more decisive than warranted. This is a general statistical consideration, not a reported feature of this trial. The endpoint is described as continuous and analyzed with repeated-measures ANOVA; the registry record does not report an over-dispersion assessment or indicate that over-dispersion was identified.

The arm summaries list standard deviations, but those alone do not establish whether model assumptions were satisfied. Assessment would require information about the analysis and data that is not reported in the registry record. The published comparison should therefore be interpreted with its stated summary and with attention to the absent methodological details, rather than assuming either that a problem occurred or that all assumptions were verified.

10. Confidence Intervals and Precision

The mean difference is -6.588 units, and the confidence interval extends from -10.44 to -2.734. This interval communicates the uncertainty around the estimated group contrast under the analysis used. The full interval lies on the negative side of zero, so the estimate is compatible with a lower mean in the Setraline arm than in placebo under that analysis. The interval does not show the range of scores among individual participants.

Precision concerns how narrowly an effect has been estimated. In general, a narrower interval indicates greater statistical precision, while a wider interval indicates more uncertainty about the effect's magnitude. The interval still permits a range of possible differences, rather than identifying one exact value as the true contrast. Its interpretation also depends on the assumptions and analysis that generated it, whose details are not fully reported in the registry record.

The registry lists standard deviations of 5.493 and 6.141 for the two arms. These describe variability in the observed outcome, whereas the confidence interval describes uncertainty in the estimated difference. The posted outcome counts are 20 and 16, and enrollment is 47. The record does not explain the relationship between enrollment and the counts used for this outcome, or how missing measurements were handled. That limits what can be concluded about the precision of an estimate for all enrolled participants.

The interval does not address uncertainty from outcome selection, multiple testing, model choice, or potential departures from assumptions. The p-value is unadjusted, and no multiplicity plan is reported. The precision conveyed by the interval should therefore be understood as conditional on the analysis behind it, not as a guarantee that all relevant uncertainties have been captured.

11. 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 sample-size figures are planning illustrations based on fractions of the observed effect, not the original trial's design justification. They are participants per arm, not total events. The registry record lists a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It says the effect to detect is the stated fraction of the observed effect. The trial's own original design assumptions are not reported in the registry record.

The 80% power column describes the number of participants per arm in the planning calculation for an 80% chance of detecting the specified effect under those assumptions. The 90% power column describes the corresponding planning number for a 90% chance. These are design targets, not statements about what happened in the completed trial. The values are 13 and 17 participants per arm for planning for 100% of the observed effect; 22 and 29 for planning for 75% of the observed effect; and 49 and 65 for planning for 50% of the observed effect, respectively.

Smaller effects are harder to distinguish from random variation, so planning to detect a smaller effect requires more participants under the same assumptions. The curve represents this relationship between the effect size used for planning and the required sample size. These values are not observed power: they are forward-looking planning illustrations computed from the observed effect, not a measure of the trial's achieved evidential strength.

12. 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 = -6.588; pooled standard deviation σ = 5.788.
2. n = 2 × (1.96 + 0.842)² × 5.788² / -6.588² = 12.1, rounded up to 13 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 <- -6.58799999999999                      # observed difference in means
sigma <- 5.78783243486866                     # 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(1996644)
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 = 13 (80% power), 17 (90% power)
 75% of observed effect: n per arm = 22 (80% power), 29 (90% power)
 50% of observed effect: n per arm = 49 (80% power), 65 (90% power)
power.t.test: 13.1 
Simulated power at n = 13 per arm: 0.797 (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.

13. Multiplicity, Missing Data and Analysis Populations

The primary anxiety comparison is reported with an unadjusted p-value. The registry record does not report a plan for controlling multiplicity, such as how testing across outcomes, time points, or other analyses was to be handled. The study summary states expectations about anxiety and BMI, and the record lists three outcome measures, but no secondary outcomes are posted in the results summarized for this trial. It also lists one analysis. These entries do not establish what hypotheses were prespecified or whether any additional analyses were conducted.

Multiplicity matters when several statistical tests are considered. In general, the more tests performed, the greater the chance that at least one result may appear noteworthy by chance if each test is interpreted separately. An adjustment or a prespecified hierarchy can address some multiplicity concerns, but the registry record does not report whether either was used. The unadjusted p-value should therefore be interpreted as a result for the reported comparison, not as evidence that testing across all possible outcomes has been accounted for.

The registry record does not report missing-data methods, the number of participants with measurements at each session, or reasons for missing outcome data. The enrollment is 47, while the outcome counts are 20 and 16; the record does not explain the difference. It also does not state whether the analysis included all randomized participants, only participants with available measurements, or another analysis population. The population used in the analysis is therefore not reported in the registry record.

For repeated measurements, missing observations can affect which participants contribute information at each session and how the model handles incomplete records. In general, the consequences depend on why measurements are missing and on the method used. Neither the pattern of missingness nor the handling method is reported, so the direction or size of any possible influence cannot be determined from the registry record.

14. 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 0% reporting threshold.

The serious adverse event figures list 20 participants at risk in the Setraline arm and 16 in placebo. The number affected by serious adverse events is recorded as 0 in each arm. The other adverse event figures also list 20 and 16 at risk, with 0 affected in each group. No serious adverse event terms are listed.

These entries describe the safety counts recorded for the groups and outcomes listed; they are not a complete account of every possible safety concern. The deaths field is not populated with a value, so deaths are not reported in the registry record. The record does not provide additional detail about event definitions, collection procedures, follow-up duration for safety, or whether events were assessed for relatedness to an intervention.

A count of zero affected in these entries means that the registry records no participants affected in the listed categories and groups. It does not establish that an event could not occur, or that all possible events were fully observed. The listed at-risk counts are the relevant denominators for reading these figures, and should not be replaced with the trial enrollment count.

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

The posted primary comparison shows a lower mean anxiety score in the arm labeled Setraline than in the placebo arm. The reported mean difference is -6.588 units, with a confidence interval from -10.44 to -2.734 and an unadjusted p-value of p < 0.001. Since the scale defines lower scores as less anxiety, the direction of the reported group contrast is toward lower anxiety scores in the Setraline arm.

This result does not by itself show that the intervention caused the observed difference. The trial is randomized, but the registry record does not report important details about the analysis population, missing data, session-level measurements, or the model specification. The trial title calls the study double blind while the masking field says triple, and the drug naming is inconsistent. These record details should remain visible when interpreting the comparison.

The reported mean difference is a group average contrast, not a description of each participant's experience. The outcome description says repeated measurements were combined, but the results do not show the individual or session-specific patterns. They therefore cannot establish when a difference arose or whether it was maintained across sessions. The confidence interval expresses statistical uncertainty under the reported analysis, not certainty about the result or coverage of all potential sources of uncertainty.

The registry summary states expectations about BMI, but no BMI result is reported in the registry record. The anxiety result also does not establish broader effectiveness, safety, or applicability to people beyond the trial population. The registry safety entries record zero affected by serious adverse events in both groups, but deaths and additional safety details are not reported. The findings should be read as a record of one pilot trial's posted outcome, not as medical advice or a definitive conclusion about treatment.

16. Why This Trial Matters Statistically

This trial is statistically notable for combining a continuous anxiety measure with repeated observations across four sessions. Repeated measurements can provide information about outcomes over time, but they require attention to within-participant correlation and to how incomplete session data are handled. The registry description identifies a repeated-measures ANOVA, yet does not report its model specification or session-level results. That gap illustrates why a method label alone is not enough to evaluate a longitudinal analysis.

The posted mean difference, confidence interval, and unadjusted p-value illustrate complementary summaries. The estimate conveys the direction and size of the reported contrast in scale units; the interval conveys uncertainty around it; and the p-value addresses compatibility with a null model under a test. Keeping these interpretations distinct avoids treating statistical significance as a measure of effect size or certainty.

The record also shows why registry labels require careful reading. It identifies DCS as the study medication in the summary but uses Setraline in intervention and arm labels, including a phrase that combines both names. The title and masking field also differ in their descriptions. These inconsistencies do not invalidate the numerical comparison, but they constrain how confidently the intervention and procedures can be characterized from this record.

Finally, the planning illustration relates required participants per arm to fractions of the observed effect. It helps explain why smaller target effects require larger planning samples under stated assumptions. It is distinct from the completed trial's evidence and cannot substitute for a protocol-based design rationale or the missing details about the original sample-size assumptions.

17. 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 does not report detailed eligibility criteria, the analysis population, missing-data methods, or participant counts at each anxiety session. Enrollment is 47, while the reported outcome groups contain 20 and 16 participants; the reason for that difference is not stated. As a result, it is not possible to determine from the record how the primary comparison relates to all enrolled participants or whether incomplete outcome data affected the analysis.

The endpoint description refers to a repeated-measures ANOVA but does not give the model specification, session-level scores, assumptions checks, or exact method used to combine measurements. No BMI result is posted, even though BMI increase appears among the study's stated expectations. The registry lists three outcome measures and one analysis, but does not clarify the prespecified outcome hierarchy or multiplicity handling.

The intervention naming is inconsistent: the study summary identifies cycloserine (DCS), while intervention and arm labels use Setraline and the arm description includes 250 mg DCS (setraline). The record does not resolve which name is intended. Likewise, the title says double blind, while the masking field says triple; the masking procedures are not described.

The study is described as a pilot. The original sample-size justification and design assumptions are not reported in the registry record. The planning figures based on the observed effect are illustrations rather than the trial's original design rationale. Safety information is also limited: the listed affected counts are zero, but deaths are not reported in the registry record, and event definitions and follow-up details are absent. These omissions limit the scope of conclusions that can be drawn from the posted results.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: A Double Blind Clinical Trial of DCS for Food Anxiety — NCT01996644.
• Registry record last updated 2018-03-27; status last verified 2018-03.
• Results first posted 2018-03-27.
• 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.

21. Record Summary

NCT01996644 is a completed randomized, parallel-group pilot study of exposure therapy with DCS or placebo for food anxiety in patients with anorexia and bulimia nervosa. Enrollment is 47, and the study start and primary completion are recorded as 2013-02 and 2014-02. The title describes double blinding, while the masking field records triple masking. The phase is listed as NA.

The primary outcome is anxiety on the Subjective Units of Distress scale, measured at four sessions over two weeks. The posted means are 52.4 for Setraline and 58.98 for placebo. The reported mean difference is -6.588, with a confidence interval from -10.44 to -2.734 and p < 0.001. The intervention's name is inconsistent in the registry record, and the record does not explain the difference between enrollment and the outcome counts of 20 and 16.

The registry records zero participants affected by serious adverse events in each group; deaths are not reported. A BMI result, detailed analysis methods, missing-data handling, and the original sample-size justification are not reported in the registry record.