Safety and Effectiveness Study of Maca Root to Treat Antidepressant-Induced Sexual Dysfunction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety and Effectiveness Study of Maca Root to Treat Antidepressant-Induced Sexual Dysfunction (NCT00181961), a randomized phase 3 study. The primary outcome is Change in Massachusetts General Hospital Sexual Dysfunction Inventory Scores.

2. Clinical Question

The study asked whether sexual dysfunction among patients with major depressive disorder taking antidepressants changed after treatment with Maca Root, and whether the observed change differed between two doses. It was described as a dose-finding pilot study focused on identifying a minimum effective dose. The registry record describes the population as patients with DSM-IV defined Major Depressive Disorder and antidepressant-induced sexual dysfunction.

The registry record gives a mean change of 0.249 in the 1500mg group and 0.017 in the 3000mg group. It also reports a Wilcoxon (Mann-Whitney) analysis with p = .016. The outcome description gives score thresholds for improvement, no change, and dysfunction, but does not state how the direction of a change score is coded. The score averages and the test result should therefore be read with that limitation in mind.

3. Trial Design

This was a randomized, quadruple-masked, parallel-group Phase 3 study sponsored by Massachusetts General Hospital. The registry record lists 20 participants as the enrollment and marks the study completed. Its recorded start was 2007-12 and its primary completion was 2010-06. The stated purpose was dose-finding in people with antidepressant-induced sexual dysfunction.

Participants were assigned to one of two Maca Root dose groups: 1500mg or 3000mg. The registry record describes the group assignments as randomized and the masking as quadruple, but does not specify which people were masked or how randomization and masking were implemented. Details of sequence generation, allocation concealment, adherence, treatment duration beyond the endpoint timeframe, and any co-interventions are not reported in the registry record.

The primary endpoint was change in Massachusetts General Hospital Sexual Dysfunction Inventory scores from baseline to endpoint at 8 weeks. The posted arm summaries include 7 participants in the 1500mg group and 9 in the 3000mg group. The registry record lists 20 enrolled overall, so the posted endpoint group counts do not account for every enrolled participant; reasons for the difference and the analysis population are not reported in the registry record.

The comparison is between two doses rather than between Maca Root and an untreated or placebo group. Consequently, the reported comparison addresses the relative results for these two dose groups within this study. Without a separate control group, these results alone do not establish how either group would have changed without Maca Root. The registry record does not report a sample-size justification or explain whether the study was designed to provide a definitive efficacy comparison.

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

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 in Massachusetts General Hospital Sexual Dysfunction Inventory Scores, measured over baseline to endpoint (8 weeks).

The primary endpoint was change in Massachusetts General Hospital Sexual Dysfunction Inventory scores from baseline to endpoint at 8 weeks. This is a continuous measure: each participant has a score, and the registry record reports the mean and standard deviation for each dose group. A change score is intended to describe how a measurement differs between the starting assessment and a later assessment, rather than simply describing the endpoint score by itself.

The inventory is used to assess sexual dysfunction. The registry description states that its minimum score is 5 for men and 4 for women, and its maximum is 30 for men and 24 for women. It also states that a score of 5 for men or 4 for women indicates improvement in sexual function; a score of 10 for men or 8 for women indicates no change; and a score higher than 10 for men or 8 for women indicates a level of sexual dysfunction. One item applies only to men.

These details explain the measure’s intended clinical interpretation, but the registry record does not clarify how those thresholds relate to the reported change values, or how positive and negative changes are coded. It also does not report separate results by sex. The endpoint provides a way to summarize change in the measured domain, but its clinical meaning depends on the score coding and the context of the participants’ baseline scores.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous, so its values can be summarized by a mean and a measure of spread. The registry record reports the mean change and standard deviation for each dose group. The mean is the arithmetic average of the observed values in a group. The standard deviation describes how spread out individual values are around that group’s mean; it is not the uncertainty interval for the mean and is not a measure of the treatment effect.

The registry record’s inferential comparison uses the Wilcoxon (Mann-Whitney) method. This is a rank-based approach for comparing observations from two independent groups. Rather than directly comparing group means, it orders the values and uses their ranks to assess whether observations in one group tend to be higher or lower than those in the other. It can be useful when a normal-distribution model for the outcome is not appropriate, but its interpretation depends on the distributions being compared. Without additional assumptions, a result from this test is not simply a test of equal means or a direct estimate of a shift in the outcome.

The reported p-value is .016. A p-value measures how incompatible the observed test result is with a specified null model, assuming that model and the test assumptions hold. It is not the probability that the null hypothesis is true, and it does not quantify the size of a group difference. A small p-value can occur alongside substantial uncertainty about the effect’s magnitude, particularly when the estimate and its confidence interval are not reported. The registry record does not state whether the reported p-value is one-sided or two-sided.

What would an effect estimate add?

An effect estimate would express the contrast between the dose groups on a clearly defined scale. A confidence interval around that estimate would convey its precision by showing a range of values compatible with the data under the analysis. The registry record does not report an effect estimate or confidence interval for the two-group comparison. It also does not report enough detail to reconstruct the rank-based comparison from group means and standard deviations alone. Those summaries do not preserve the ordering of individual observations that the Wilcoxon (Mann-Whitney) test uses.

Why does over-dispersion matter?

General: over-dispersion means that observed variation is greater than a statistical model expects. If a model assumes less variation than the data contain, standard errors can be too small and uncertainty can be understated. This endpoint is continuous, and the registry record does not report a model-based analysis or describe over-dispersion as an issue. The general principle is relevant when selecting and checking models, but it should not be read as a claim that over-dispersion occurred in this study.

What can the group summaries tell readers?

The means and standard deviations describe the posted outcome summaries within each dose group. They do not reveal the shape of each group’s data, whether there were outliers, or whether participants’ scores clustered around the mean. The endpoint counts are 7 and 9, while the record lists 20 enrolled. How the endpoint analysis handled participants without an outcome value is not reported in the registry record. This matters because excluding participants with missing measurements can affect both the summaries and the comparison, depending on why data are missing and how missingness relates to outcome.

What does randomization contribute?

General: random assignment aims to make treatment groups comparable, on average, with respect to factors measured and unmeasured before assignment. In a small trial, chance differences between groups can still occur. The record identifies the study as randomized, but details of sequence generation, concealment, baseline balance, and the analysis population are not reported in the registry record. Masking can reduce some forms of bias in treatment delivery and outcome assessment, but the record does not specify who was masked or how masking was maintained.

What do planning assumptions mean?

General: sample-size planning can estimate how many participants might be needed to detect a target effect under specified assumptions, such as a significance level, allocation, and statistical model. Any sample-size values derived from an observed effect are planning illustrations, not observed power and not proof that the study had adequate power. The registry record does not report the trial’s own sample-size justification or a planned target effect. The assumptions attached to planning illustrations are not evidence that those assumptions were the original protocol’s design assumptions.

The registry record lists one primary outcome measure and one reported analysis, and no secondary outcomes. It does not describe an analysis plan, a hierarchy of hypotheses, adjustment for multiple testing, interim analyses, or rules for handling missing data. Such details help readers judge whether the reported analysis followed a prespecified plan and whether the reported p-value should be interpreted alongside other analyses. Their absence from the registry record does not establish that these procedures were or were not used.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Maca Root 1500mg", "Maca Root 3000mg")
n   <- c(7, 9)
m   <- c(0.249, 0.017)
sp  <- c(2.39, 1.15)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Maca Root 1500mg  7  0.249  2.390  -1.961  2.459
CARM  Maca Root 3000mg  9  0.017  1.150  -0.867  0.901

11. Analyses Reported by the Sponsor

The inferential result reported in the registry record is the Wilcoxon (Mann-Whitney) comparison between the 1500mg and 3000mg groups, with p = .016. No comparison estimate or confidence interval is reported alongside it. The record also does not provide the individual-level data needed to reconstruct the rank-based test from the posted means and standard deviations alone.

No separate recalculated comparison estimate or confidence interval is available in the registry record. The record does not flag a discrepancy between the reported analysis and a recalculation. Accordingly, there is no numerical recalculation to use as a competing result or to reconcile with the sponsor-reported test. The reported analysis remains the only posted inferential comparison for this endpoint.

The group means and standard deviations are descriptive summaries, not a substitute for the sponsor’s rank-based analysis. In particular, a comparison calculated from summary means would not reproduce a Wilcoxon (Mann-Whitney) test, which depends on the ordering of participant-level outcomes. The registry record does not report the test statistic, a treatment-effect estimate, or a confidence interval, so the p-value cannot be paired with a precise estimate of the size of the difference.

12. Multiplicity, Missing Data and Analysis Populations

The registry record lists one outcome measure and one analysis. It does not list secondary outcomes. On the information recorded, there is a single posted endpoint and a single posted inferential comparison to describe. However, the registry record does not report whether additional outcomes, analyses, dose contrasts, or subgroups were considered outside the posted results. It also does not report a prespecified analysis plan or a multiplicity strategy.

Multiplicity arises when researchers conduct several statistical tests or select among several analyses. Repeated testing can increase the chance that at least one result appears statistically notable even when no corresponding effect exists. Methods such as adjustment or a prespecified hierarchy can address this issue, but whether any such approach was used is not reported in the registry record. With only one listed analysis, the record does not establish that no other analyses were performed.

Missing-data handling is also not reported in the registry record. The listed enrollment is 20, whereas the primary endpoint summaries include 7 participants in the 1500mg group and 9 in the 3000mg group. The record does not explain why the posted endpoint counts do not cover all enrolled participants, whether some participants lacked endpoint measurements, or how any missing values were handled. It does not identify the analysis population as intention-to-treat, per-protocol, or another defined group.

These omissions matter because the interpretation of a randomized comparison depends not only on assignment but also on which participants contribute to the analysis and how incomplete measurements are addressed. If participants with missing outcomes differ systematically from those with observed outcomes, the analyzed groups may not retain the balance intended by randomization. This is a general concern, not evidence that such bias occurred in this study. The registry record does not report sensitivity analyses or other checks addressing missing outcomes.

13. 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 non-serious adverse event terms

The serious adverse event figures list 0 affected participants among 7 at risk in the 1500mg group and 0 among 9 at risk in the 3000mg group. These figures describe the counts recorded for the posted groups. They do not show that serious adverse events are impossible or that no such events occurred outside the participants and period represented by the record.

The registry record also lists other adverse events affecting 5 of 7 participants in the 1500mg group and 7 of 9 in the 3000mg group. These are counts, not estimates of comparative risk adjusted for differences between groups. The record does not provide details of event types in the serious-event list, and no serious-event terms are listed. Death counts are null, which means they are not reported in the registry record; they should not be interpreted as zero deaths.

Safety counts from groups of this size are limited in their ability to characterize uncommon events or compare safety reliably. The registry record does not report event timing, severity beyond the serious/non-serious distinction, relatedness to treatment, or whether participants could have more than one event. These figures are descriptive and should be read in the context of the small posted group counts and the incomplete detail recorded.

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

The posted results describe change in a sexual-dysfunction inventory among participants assigned to two Maca Root doses. The group means were 0.249 for 1500mg and 0.017 for 3000mg; the reported Wilcoxon (Mann-Whitney) comparison gave p = .016. These values are the registry record’s reported summaries and inferential result. The score description offers sex-specific thresholds for interpreting inventory scores, but the record does not explain how those thresholds map onto the change values or state the sign convention for change.

The p-value indicates a statistically notable result under the reported rank-based test and its assumptions. It does not tell readers how large the difference was, how precise an estimated difference might be, or whether any difference meets a clinical threshold. No confidence interval or effect estimate is reported for the comparison. The p-value also does not establish that one dose is effective, or that either dose is better than no Maca Root, because both groups received Maca Root.

The study was described as a dose-finding pilot, but the registry record does not report a dose-selection rule or the criterion for a minimum effective dose. The results therefore do not, on their own, identify a minimum effective dose. They also do not establish how results would apply to people outside the recorded study population, or how results would compare with a placebo or another treatment.

The posted endpoint counts are smaller than the listed enrollment, and the record does not explain the analysis population or missing-data handling. The absence of those details limits the assessment of potential bias. The results should be understood as a small-study comparison with incomplete reporting of effect size, precision, and analysis details, rather than a complete account of all evidence relevant to treatment effects or safety.

15. Why This Trial Matters Statistically

This trial raises several useful statistical questions for clinical researchers. Its purpose was dose-finding, and its two randomized groups received different doses of the same intervention. That design can inform a comparison between those doses, but it does not provide a no-treatment or placebo comparison. Matching the statistical interpretation to the actual comparison is essential: a result between active doses is not an estimate of the effect of either dose versus no intervention.

The registry record reports both group means and a rank-based test. These summaries illustrate why descriptive and inferential results should not be treated as interchangeable. Means describe averages, while a rank-based method compares the ordering of observations. Without a clear effect estimate and confidence interval, readers cannot judge the magnitude and precision of the contrast from the p-value alone.

The outcome description also highlights how measurement coding affects interpretation. Although the inventory’s score thresholds are described, the record does not explain how they relate to the change values or state the direction convention for change. Clear reporting of baseline scores, endpoint scores, change coding, and clinically meaningful thresholds would help readers connect statistical results with the construct being measured.

Finally, the enrollment and endpoint group counts differ, while the handling of missing outcomes is not reported. This is a reminder that reporting the analysis population and missing-data approach is part of interpreting a randomized trial, not a technical detail that can be separated from the results. Transparent reporting of the planned analysis, effect estimates, uncertainty intervals, and participant flow would make the evidence easier to evaluate without relying on a p-value as a stand-in for the full result.

16. 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 posted endpoint groups are small, with 7 participants in the 1500mg group and 9 in the 3000mg group. The registry record lists 20 enrolled overall, but does not explain the difference between enrollment and the endpoint group counts. It does not report participant flow, reasons for missing endpoint data, or which analysis population was used. These gaps make it difficult to assess how representative the posted summaries are of the enrolled participants.

The registry record does not provide an effect estimate or confidence interval for the primary comparison. Although the group means and standard deviations are reported, they do not allow reconstruction of the rank-based Wilcoxon (Mann-Whitney) test. The report also omits the test statistic and does not state whether the p-value is one-sided or two-sided. Consequently, the magnitude and precision of the between-group comparison cannot be evaluated from the inferential result alone.

The score description includes different ranges and thresholds for men and women, and notes that one item applies only to men. The registry record does not report the sex composition of the analyzed groups, sex-specific results, or how the score was handled across these forms. It also does not state the direction convention for the change score. These omissions limit interpretation of the means in relation to the stated score thresholds.

Further design and analysis details are not reported in the registry record, including the randomization procedure, masking implementation, baseline outcome values, missing-data methods, sample-size justification, and multiplicity approach. The record describes the study as a dose-finding pilot but does not provide criteria for selecting a dose. These are reporting limitations; they do not demonstrate that any particular procedure was absent or that the reported comparison is invalid.

Finally, the active-dose comparison cannot determine how either dose compares with placebo or no Maca Root. The posted safety counts also provide limited detail about event timing, type, severity, and relationship to treatment. Together, these limitations support a cautious reading of the results as a small comparison with limited information about precision, analysis populations, and broader interpretation.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Safety and Effectiveness Study of Maca Root to Treat Antidepressant-Induced Sexual Dysfunction — NCT00181961.
• Registry record last updated 2019-08-21; status last verified 2019-08.
• Results first posted 2019-08-21.
• 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.

20. Record Summary

The registry record describes a completed, randomized, quadruple-masked, parallel-group Phase 3 study sponsored by Massachusetts General Hospital. It lists 20 enrolled participants and a study start of 2007-12, with primary completion in 2010-06. The study was described as a dose-finding pilot for antidepressant-induced sexual dysfunction in patients with DSM-IV defined Major Depressive Disorder.

Participants received Maca Root at 1500mg or 3000mg. The primary outcome was change in Massachusetts General Hospital Sexual Dysfunction Inventory scores from baseline to endpoint at 8 weeks. The posted group summaries include 7 participants in the 1500mg group and 9 in the 3000mg group. Their reported mean changes were 0.249 and 0.017, respectively, and the reported Wilcoxon (Mann-Whitney) comparison had p = .016.

The registry record does not report a comparison effect estimate or confidence interval, the analysis population, or how missing outcomes were handled. It lists no secondary outcomes. Its serious adverse event counts were 0 in each group; deaths are not reported in the registry record.