This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Feasibility Electrical Stimulation Study for Visual Hallucinations (NCT04870710), a non-randomized na study. The primary outcome is Steady State Visual Evoked Potential (ssVEP).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04870710 |
| Phase | NA |
| Condition | Schizophrenia, Schizoaffective Disorder, Bipolar Disorder |
| Allocation | Non-Randomized |
| Design model | Sequential |
| Masking | None (open label) |
| Enrollment | 6 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Beth Israel Deaconess Medical Center |
| Results posted | Yes |
2. Clinical Question
Population
The registry lists people with schizophrenia, schizoaffective disorder, or bipolar disorder. The enrollment was 6. Further eligibility details, including how visual hallucinations were defined for enrollment, are not reported in the registry record.
Intervention
The study concerns transcranial electrical stimulation. One arm is described as cathodal transcranial direct current stimulation (tDCS) to the bilateral extrastriate visual cortex. The other is described as anodal transcranial alternating current stimulation (tACS), delta phase aligned. Each arm description specifies two, twenty minute sessions for 5 days, with 10 total sessions.
Comparator
The registry labels allocation as non-randomized and the model as sequential. The arms therefore should not be read as a randomized, like-for-like control comparison. The precise sequence and how participants entered each arm are not reported in the registry record.
Primary question
The primary measure is the steady state visual evoked potential (ssVEP), in microvolts. It is described as measuring change in the P100 evoked response, an electrical marker of early visual processing, at baseline, 5 day, and 1 month visits. The stated timeframe compares day 5 with day 0. The clinical rationale is to examine whether stimulation directed at visual cortex is accompanied by changes in visual brain activity and visual symptoms. Numerical results for this measure are not reported in the registry record.
3. Trial Design
This completed feasibility study is registered as NCT04870710 and sponsored by Beth Israel Deaconess Medical Center. The recorded start date is 2020-10-01, the primary completion date is 2022-01-01, and the status is completed. The phase is listed as NA. Enrollment is 6, and the listed conditions are schizophrenia, schizoaffective disorder, and bipolar disorder.
The design is described as non-randomized, non-masked, and sequential. Those labels matter when interpreting any contrast between the stimulation groups: assignment was not randomized, and the registry explicitly cautions that the arms are not a like-for-like control comparison. The exact order of treatment, allocation procedure, and any within-participant sequence details are not reported in the registry record. No masking is recorded.
The intervention is transcranial electrical stimulation. The cathodal tDCS arm is described as targeting bilateral extrastriate visual cortex, with two, twenty minute sessions for 5 days and 10 total sessions. The anodal tACS arm is described as delta phase aligned, with the same session schedule. The adverse-event group label calls the tACS intervention 2hz, while the intervention description uses delta phase aligned; the registry record does not explain the difference in wording.
The primary measure is ssVEP amplitude, with secondary measures listed for affective picture processing, velocity discrimination, visual spatial working memory, and global assessment of function. The record lists 16 outcome measures and 1 analysis, but does not provide enough detail to establish the full analysis plan or the study's allocation sequence. The feasibility framing and small enrollment mean that estimates, if reported, would need cautious interpretation rather than being treated as definitive comparative evidence.
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: Participants were first consented and met with a trained medical professor review any medical changes or relevant changes to diagnosis to ensure safe measures for tES treatment. Individuals who were recruited were then requested to completed a clinical assignment as well as baseline measurements for EEG and behavioral tasks before receiving any tES treatment.
Overall Study
| Stage | Transcranial Electrical Stimulation (tES) |
|---|---|
| STARTED | 6 |
| Transcranial Direct Current Stimulation (tDCS) Baseline Assessment | 6 |
| Transcranial Direct Current Stimulation (tDCS) Five Day Follow-up Assessment | 6 |
| Transcranial Direct Current Stimulation (tDCS) 1 Month Follow-up Assessment | 5 |
| Transcranial Alternating Current Stimulation (tACS) Baseline Assessment | 4 |
| Transcranial Alternating Current Stimulation (tACS) 5 Day Follow up Assessment | 4 |
| Transcranial Alternating Current Stimulation (tACS) 1 Month Follow up Assessment | 3 |
| COMPLETED | 3 |
| NOT COMPLETED | 3 |
Reasons for not completing this period:
| Reason | Transcranial Electrical Stimulation (tES) |
|---|---|
| Lost to Follow-up | 3 |
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
Population: The total number of participates recruited was 6 individuals. However, we utilized a cross-over design with 6 individuals completing the cathodal tDCS condition (baseline and day 5) and 4 individuals completing the tACS condition (baseline and day 5) .
| Characteristic | Unit | Transcranial Electrical Stimualtion |
|---|---|---|
| Participants analysed | 6 | |
| Age, Continuous | years | 29.67 (SD 2.58) |
| Sex/Gender, Customized: Male | Participants | 2 |
| Sex/Gender, Customized: Female | Participants | 3 |
| Sex/Gender, Customized: Transgender | Participants | 1 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 2 |
| Race (NIH/OMB): White | Participants | 3 |
| Race (NIH/OMB): More than one race | Participants | 1 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
6. Primary Endpoint
The registry lists the primary outcome as Steady State Visual Evoked Potential (ssVEP), measured over Measured at day 5 compared to day 0.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | microvolts |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the steady state visual evoked potential (ssVEP), measured in microvolts. The registry describes it as a measure of the average evoked response potential amplitude change for P100 at baseline, 5 day, and 1 month visits. Its stated timeframe is day 5 compared with day 0. The role of the 1 month visit in the primary comparison is not specified further in the registry record.
The ssVEP is used in the study as an electrical biomarker of early visual response. Participants viewed a black and white square oscillating at 18.75 Hz for 2000 ms. The stimulus was presented in the central, bilateral, left, or right visual field; the description specifies 50 trials and 200 total trials pseudorandomly interleaved, with inter-trial intervals of 2.5 seconds. These details describe the task used to evoke and measure visual responses, rather than a direct count of visual hallucinations.
The registry specifies the median as the summary parameter and the inter-quartile range as the dispersion measure. In general, the median gives the middle of an ordered set of observations, while the inter-quartile range describes the spread of the central portion of those observations. This approach can be useful when measurements are skewed or affected by extreme values. The record does not report the observed endpoint values, their variability, or an estimated change between visits, so the size and precision of any change cannot be assessed from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes a feasibility study of visual-cortex stimulation and specifies an electrical biomarker as its primary measure. It does not report numerical results for the primary ssVEP endpoint. As a result, the direction, magnitude, and precision of the primary outcome cannot be determined from the registry record. There is no basis in the posted information for describing the measured response as having increased or decreased, or for judging whether any change was compatible with no change.
The outcome description spans baseline, 5 day, and 1 month visits, while the stated primary timeframe is day 5 compared with day 0. That gives some information about the intended measurement timing, but not about the observed values or the analysis used to compare visits. Numerical estimates, confidence intervals, and p-values for the endpoint are not reported in the registry record. Without an estimate and its uncertainty, readers cannot judge how precisely a potential change was measured or how compatible the results would be with a range of effects.
The design also limits the interpretation of comparisons between intervention groups. Allocation was non-randomized, masking was absent, and the registry cautions that the arms are not a like-for-like control comparison. In general, non-randomized group differences can reflect participant characteristics, treatment order, or other differences alongside an intervention effect. The record does not describe the allocation process or provide enough detail to determine how those possibilities were addressed. The sequential label alone does not establish what sequence participants followed.
Enrollment was 6. In a study of this size, estimates can be highly sensitive to individual observations, and apparent group patterns may be imprecise. That general caution does not establish that the actual data were unusually variable; the endpoint results and their spread are not reported in the registry record. The sample size should therefore be read as the number enrolled, not as evidence that the study had sufficient precision to resolve a treatment effect.
The registry lists additional measures involving affective pictures, velocity discrimination, visual spatial working memory, and global assessment of function. It does not provide numerical results for these measures in the information recorded. Nor does the brief summary's rationale—investigating brain activity, visual processing, and hallucinations—substitute for measured outcomes. The posted information supports describing what the study set out to examine, but does not support claims about the outcome of stimulation, changes in hallucinations, or clinical benefit.
Any planning illustrations based on the observed effect are not observed power and should not be read as proof that the study was adequately sized. Such illustrations depend on assumptions about the effect to detect and the analysis. The registry's own sample-size justification and statistical plan are not reported in the registry record. Because numerical primary results are also absent, readers cannot independently relate any planning illustration to a posted endpoint estimate.
9. Statistical Methods Explained
The study's registry labels describe the broad design, but the record does not provide a complete statistical analysis plan. The terms below explain general statistical concepts relevant to interpreting the measures and design; they do not establish which procedures were actually used beyond what the registry states.
What does the median and inter-quartile range convey?
The primary endpoint is summarized using a median and inter-quartile range. In general, the median is the central observation after measurements are ordered. The inter-quartile range describes the spread between the lower and upper portions of the ordered observations. Together, these summaries can communicate both a typical value and variability without assuming that measurements follow a symmetric distribution. They do not, by themselves, quantify uncertainty in a treatment contrast. Confidence intervals or other uncertainty estimates would be needed to show how precisely an estimated change or group difference is determined. Such estimates are not reported in the registry record.
Over-dispersion is a general concern when observed variability is greater than a statistical model assumes. If a model underestimates variability, its uncertainty estimates may be too narrow and tests may appear more decisive than warranted. This is a general reason to examine the distribution and variability of data and to match analysis assumptions to the measurement. The registry record does not report a model for the primary endpoint, diagnostic checks, or a method for handling over-dispersion.
What does the non-randomized design imply?
Random allocation is generally used to make treatment groups comparable, on average, with respect to measured and unmeasured characteristics. Here, allocation is recorded as non-randomized. This means group comparisons cannot automatically be interpreted as if treatment assignment had been randomized. Differences between groups could reflect who entered each group or when they received an intervention, in addition to any effect associated with stimulation. The registry explicitly cautions that the arms are not a like-for-like control comparison.
The model is labeled sequential, but a label alone does not specify the order, transition rules, or whether observations from the same participant contribute to multiple treatment conditions. Those details are not reported in the registry record. Without them, readers cannot determine whether a paired analysis, a between-group analysis, or another approach would be appropriate. The actual model used for analysis is not reported in the registry record.
Masking is listed as none. In general, awareness of the intervention can influence subjective ratings, participant behavior, or decisions in outcome assessment. The primary endpoint is an electrical response rather than a self-report, but that alone does not establish that acquisition or analysis was insulated from knowledge of treatment. The registry record does not describe assessor masking or procedures to limit measurement bias.
How should a confidence interval or p-value be read?
In general, a confidence interval expresses uncertainty around an estimated quantity under a specified statistical procedure. Its width reflects the precision of the estimate: wider intervals indicate greater uncertainty, while narrower intervals indicate greater precision under the model. A p-value, when used, describes how unusual data at least as incompatible with a specified null model would be under that model's assumptions. Neither quantity alone establishes clinical importance or removes design limitations. The registry record does not report a confidence interval or p-value for the primary endpoint, nor does it report the statistical test or model used.
Effect estimates and uncertainty are especially important in a small feasibility study. A single observation can have substantial influence on a summary when enrollment is limited. In general, this makes estimates less stable and limits what can be inferred about the size of an effect. It does not mean that a result is necessarily biased or that a particular estimate is wrong; it means that precision and the analysis population need to be visible for a reader to judge the evidence. Numerical results and analysis-population details are not reported in the registry record.
What do planning illustrations mean?
General sample-size planning asks how many participants would be needed to detect a target effect under stated assumptions about variability, significance level, allocation, and statistical method. The registry notes that its planning illustrations use a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation, with the target effect expressed as a stated fraction of the observed effect. These are planning assumptions, not a record of the trial's design justification. The registry's own sample-size justification is not reported in the registry record.
Such illustrations are hypothetical planning quantities, not observed power. Observed power is not a substitute for reporting the estimated effect and its uncertainty. The record does not give the numerical observed effect or the calculated participant counts in the information available for this analysis, so no planning value can be interpreted. In general, an illustration based on a small study's observed effect can be particularly unstable because that estimated effect may be imprecise.
What is not specified?
The registry lists 16 outcome measures and 1 analysis, but does not specify the complete model, covariates, handling of repeated measurements, missing-data method, analysis population, or multiplicity procedure. These details affect how estimates and uncertainty should be understood. They should not be inferred from the endpoint description or the design labels. The record also does not report interim analyses, stopping rules, or a prespecified sample-size calculation. Their absence from the registry information should be read as missing documentation, not as proof that any particular procedure was or was not used.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 16 outcome measures, including repeated listings for the International Affective Picture System task, velocity discrimination, visual spatial working memory, and global assessment of function. It reports 1 analysis. These counts do not reveal how many hypotheses were tested, which outcomes were designated primary or secondary in the analysis plan, or whether each listed measure represents a distinct comparison. The detailed multiplicity strategy is not reported in the registry record.
In general, evaluating many outcomes or contrasts can increase the chance of finding a nominally unusual result even when no underlying effect exists. Statistical procedures can address this through adjustments, hierarchical testing, or a clear distinction between confirmatory and exploratory analyses. The registry record does not report whether any such approach was planned or used. Consequently, no claim about adjustment or unadjusted testing is warranted.
Missing-data handling and analysis populations also affect interpretation. The record does not report how missing visits or incomplete measurements were handled, whether all enrolled participants were included in each analysis, or whether analyses followed a prespecified population definition. These items are not reported in the registry record. Enrollment of 6 alone does not indicate how many participants contributed usable data at each visit or to each outcome. The registry's primary endpoint description includes baseline, 5 day, and 1 month visits, but does not give completion counts by visit. Without those details, readers cannot assess whether missingness may have influenced the estimated changes.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Cathodal Transcranial Direct Current Stimulation (tDCS) | 0 | 6 | 0.0% |
| 2hz Transcranial Alternating Current Stimulation (tACS) | 0 | 4 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Cathodal Transcranial Direct Current Stimulation (tDCS) | 0 of 6 |
| 2hz Transcranial Alternating Current Stimulation (tACS) | 0 of 4 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Cathodal Transcranial Direct Current Stimulation (tDCS) | 0 of 6 |
| 2hz Transcranial Alternating Current Stimulation (tACS) | 0 of 4 |
The registry reports adverse-event counts separately for cathodal tDCS and tACS. In the tDCS group, 6 were at risk for serious adverse events and 0 were affected; 6 were at risk for other adverse events and 0 were affected. Deaths were 0. In the tACS group, 4 were at risk for serious adverse events and 0 were affected; 4 were at risk for other adverse events and 0 were affected. Deaths were 0. The serious-event term list is empty.
These are the counts recorded for the listed groups. They do not establish that no events could occur in a broader population or under other circumstances. In general, zero observed events in a small group still leaves uncertainty about the frequency of uncommon events. The registry record does not describe the adverse-event collection window, the monitoring procedures, or the completeness of follow-up for safety assessment. The group labels also use 2hz for tACS, while the intervention description calls it delta phase aligned; the record does not explain this wording.
The risk counts should be read as the denominators attached to each adverse-event group, not as evidence that the groups were comparable or randomized. The registry does not report any serious adverse-event terms. These figures describe recorded events; they do not establish a general safety conclusion.
12. What the Result Does, and Does Not, Mean
The study addresses a focused measurement question: whether stimulation targeting visual cortex is associated with a change in an electrical measure of early visual response. Its primary measure, ssVEP amplitude, is an objective physiological marker described in microvolts. That is relevant to the proposed mechanism, but it is not itself a direct measure of hallucination frequency, distress, or day-to-day functioning.
The registry summary gives a rationale linking visual cortex activity to visual symptoms and describes the study as a feasibility investigation. It also lists secondary measures that include visual processing tasks and global assessment of function. The registry record does not report numerical results for those outcomes or for the primary measure. Therefore, the posted information cannot establish whether brain activity changed, whether visual processing changed, or whether hallucinations changed. It also cannot establish that stimulation caused any such change.
The design further limits causal interpretation. Allocation was non-randomized, masking was none, and the record cautions against treating the arms as a like-for-like control comparison. A difference between groups, if one were reported, would not by itself distinguish an intervention effect from group differences or other factors associated with the sequence. Details needed to evaluate those possibilities are not reported in the registry record.
Feasibility work can help establish whether procedures and measures are workable and can inform later research. The registry record does not report specific feasibility outcomes, such as recruitment or completion, so those aspects cannot be evaluated from the posted information. Enrollment was 6, and no numerical primary endpoint result or uncertainty estimate is reported. The findings therefore cannot be judged for magnitude, precision, or reproducibility from this record.
The appropriate conclusion is limited to the study's scope and documentation: a completed, small, non-randomized study was registered to examine electrical stimulation and visual measures in people with psychotic disorders. The registry record describes its procedures and outcomes but does not report the results needed to assess an observed effect. It should not be interpreted as evidence that a treatment works or does not work.
13. Why This Trial Matters Statistically
This study is statistically informative as an example of the distinction between a biological marker and a clinical outcome. The primary measure is an electrical response associated with early visual processing, while the clinical rationale concerns visual hallucinations and related symptoms. A change in a biomarker would not automatically show a change in symptoms; both outcomes would need to be measured and reported to evaluate that link. The registry lists a range of additional visual and functional measures, but numerical results are not reported in the registry record.
Its design also illustrates why allocation and comparison structure matter. A sequential, non-randomized study without masking can be useful for feasibility questions, but it does not offer the same protection against confounding as randomized allocation. The registry itself cautions that the arms are not a like-for-like control comparison. Any interpretation of between-arm patterns would need to account for the design and the sequence details, which are not reported in the registry record.
Enrollment was 6, emphasizing the importance of precision rather than a simple focus on whether a result crosses a threshold. Estimates from a small study may be unstable, and confidence intervals would help communicate that uncertainty. Such endpoint estimates and intervals are not reported in the registry record. Planning illustrations, when used, are projections under assumptions and are not observed power or a substitute for outcome estimates.
Finally, registration makes clear which outcomes and procedures were described, but the absence of numerical results and analysis details limits statistical appraisal. The record does not report the multiplicity approach, missing-data methods, or complete analysis populations. Those omissions matter because readers need to know how many comparisons were considered and which observations contributed to each estimate. The central statistical lesson is that design labels and outcome definitions can frame a question, but only transparent outcome estimates and uncertainty can answer it.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The most immediate limitation is that numerical outcome results are not reported in the registry record. No primary endpoint estimate, variability estimate, confidence interval, or p-value is listed. Consequently, neither the direction nor the precision of the ssVEP change can be evaluated. Results for the listed secondary measures are also not reported in the registry information.
Enrollment was 6. This limits the amount of information available for estimating variability and makes generalization especially uncertain. The record does not say how many participants completed each visit or contributed to each analysis. The primary measure description includes baseline, 5 day, and 1 month visits, but follow-up completion by visit is not reported in the registry record.
The non-randomized allocation, absence of masking, and registry warning that arms are not a like-for-like control comparison constrain causal interpretation. The exact sequence, allocation procedure, and analysis of treatment order are not reported in the registry record. Intervention descriptions also differ in their naming of the tACS condition: the intervention is described as delta phase aligned, whereas the adverse-event group is labeled 2hz. The record does not clarify that discrepancy.
Other important statistical details are not reported in the registry record, including the full analysis plan, missing-data approach, analysis populations, multiplicity handling, and sample-size justification. The registry lists 16 outcome measures and 1 analysis, but those counts do not explain which comparisons were confirmatory or how the measures were analyzed. These limitations prevent a complete assessment of bias, precision, and the strength of any potential finding.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Feasibility Electrical Stimulation Study for Visual Hallucinations — NCT04870710.
- Registry record last updated 2025-06-12; status last verified 2025-06.
- Results first posted 2023-04-21.
- 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.
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18. Record Summary
NCT04870710 is a completed feasibility study sponsored by Beth Israel Deaconess Medical Center. The registry lists a start date of 2020-10-01, primary completion date of 2022-01-01, enrollment of 6, and conditions of schizophrenia, schizoaffective disorder, and bipolar disorder. Phase is listed as NA.
The study is described as non-randomized, non-masked, and sequential. It examines transcranial electrical stimulation, with cathodal tDCS targeting bilateral extrastriate visual cortex and an anodal tACS condition. The primary measure is ssVEP amplitude in microvolts, described as a measure of early visual response across baseline, 5 day, and 1 month visits. The stated timeframe compares day 5 with day 0.
The registry lists additional visual-processing and functional measures, 16 outcome measures, and 1 analysis. It records zero serious adverse events, zero other adverse events, and zero deaths in each listed stimulation group. Numerical primary and secondary outcome results, detailed analysis methods, and the sample-size justification are not reported in the registry record.