Transcranial Alternating Current Stimulation for Depression: Key Correction to a 2020 Clinical Trial Protocol
Major depressive disorder (MDD) impacts over 280 million people globally, making it one of the most prevalent and disabling mental health conditions. While therapy and medication help many, researchers are exploring non-invasive brain stimulation—like transcranial alternating current stimulation (tACS)—as a potential alternative or add-on treatment. A 2020 study in the Chinese Medical Journal aimed to test tACS for MDD, but the authors recently issued a correction to clarify critical details about their trial design.
The Original Study: A Gold-Standard Trial for tACS
Led by researchers including Wang HX, Wang K, Zhang WR, and colleagues from institutions in China, the study is a randomized controlled trial (RCT)—the most reliable method for testing medical interventions. RCTs work by randomly assigning participants to two groups:
- Active group: Receives real tACS (low-level electrical currents applied to the scalp to modulate brain activity).
- Sham group: Receives a “fake” version of tACS (to rule out placebo effects, where people feel better simply because they believe a treatment works).
The goal? To see if tACS leads to higher remission rates (fewer MDD symptoms) than a placebo.
The Correction: Sample Size Updated to 100 Participants
When the study was first published, it stated a total sample size of 92 participants (46 per group). The authors have since corrected this: the trial will enroll 100 participants—50 in the active tACS group and 50 in the sham group. This change reflects a more accurate calculation of how many people are needed to produce trustworthy results.
Why Sample Size Matters (And How the Authors Got It Right)
Sample size is critical for research integrity. A study that’s too small might miss real effects of a treatment (a “false negative”), while a study that’s too large wastes resources. Here’s how the authors calculated the corrected number:
- Pilot data: They used results from a smaller preliminary study, which suggested a 50% remission rate in the active group (half of participants would no longer meet MDD criteria after 8 weeks) vs. 20% in the sham group.
- Statistical power: To ensure an 80% chance of detecting a true difference between groups (called “power”) and a 5% risk of false positives (called an “alpha level”), each group needed at least 39 people.
- Attrition rate: They accounted for 20% of participants dropping out (common in long-term trials), so they increased the number to 50 per group.
The result? A total of 100 participants—enough to test tACS reliably without overrecruiting.
Transparency and Scientific Integrity
The correction was published as a corrigendum (a formal notice of error) in the Chinese Medical Journal, a peer-reviewed journal where experts vet studies before publication. This kind of transparency is key to building trust: it shows the authors are committed to accuracy, even after their work is published.
What This Means for tACS Research
For anyone following tACS as a depression treatment, this correction helps set clear expectations. The trial’s core question—Does tACS help people with MDD?—remains the same, but the larger sample size means results will be more robust. If the study finds tACS effective, it could pave the way for more accessible, non-drug treatments for depression.
Original study: Wang HX, Wang K, Zhang WR, Zhao WF, Yang XT, Wang L, et al. Protocol on transcranial alternating current stimulation for the treatment of major depressive disorder: a randomized controlled trial. Chin Med J 2020;133(1):61–67. doi:10.1097/CM9.0000000000000589
Corrigendum DOI: doi.org/10.1097/CM9.0000000000000763
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