The first clinical study of Bio-Tuningoutside the company that built it.
In 2022, a doctoral candidate at The Chicago School of Professional Psychology ran an independent 21-day intervention study to test whether Bio-Tuning's practitioner-delivered audio protocol actually reduced clinical symptoms in real patients during one of the most stressful periods in recent history.
The findings exceeded the protocol's own published timeline — sleep quality improved with a large effect size by the conventional Cohen scale, and most of that benefit had landed by the halfway mark.
Santillan, J. C. (2022).
Effects of Bio-Tuning Intervention on Stress, Depression, and Anxiety During the COVID-19 Pandemic.
Doctoral dissertation, The Chicago School of Professional Psychology (Anaheim, California). Published in the American Journal of Biomedical Science & Research.
The numbers, in context
Four of the five tested hypotheses showed statistically significant improvements with effect sizes ranging from small-to-medium(anxiety, psychological QOL) to large (sleep quality). The fifth — pandemic-specific stress — did not significantly change at the within-subject level, likely because vaccination rollouts and variant waves shifted the underlying baseline mid-study.
An effect size of d = 0.89 in 21 days is unusual.
Cohen's d is the standard way researchers measure how much a treatment moved the needle. A d of 0.2 is a small effect (most psychological interventions); 0.5 is medium; 0.8 is large. The Santillan study found d = 0.89 for sleep quality and d = 0.66 for depression — both well into clinically meaningful territory, both achieved in three weeks of nightly self-administered audio.
For comparison, an 8-week clinical trial of mindfulness-based stress reduction typically reports effect sizes in the d = 0.30–0.50 range for similar outcomes. The Santillan effect sizes exceeded that band in less than half the time.
The depression result is particularly worth dwelling on: BDI-II scores dropped from a pre-treatment mean of 12.03 (mild range) to 6.82 (minimal range) — a 43% reduction in symptom score, with statistical significance at p < 0.001. In a psychotherapy context this would be considered a substantial clinical response.
And there's one more finding worth flagging: the study was explicitly the first of its kind conducted outside any internal ties to the Center for Neuroacoustic Research. The author is unaffiliated with the Bio-Tuning organization. The practitioner who delivered the sessions was a licensed clinical psychologist (Dr. Linda Yniguez, PSY11914) running a private practice in Whittier, California.
How the study was run
Population
- • 34 adults from a private clinical practice
- • 65% female, 35% male
- • Age range 18–72 (broad demographic spread)
- • 85% Hispanic; majority from Los Angeles County
- • Convenience sample — not randomly selected
Intervention
- • One 2-hour in-office Bio-Tuning session with a CNR-certified practitioner
- • HRV measurement → personal fundamental frequency derived
- • 30-minute personalized audio file delivered to take home
- • Nightly listening (eyes closed, headphones, in bed) for 21 days
- • Adherence tracked daily
Validated measurement instruments
21 items, 0–63 scale
21 items, 0–63 scale
26 items, four QOL domains
10 items (Kato 2014, modified)
Analysis: Paired-samples t-tests for pre/post comparisons; one-way repeated-measures ANOVA for sleep quality across three timepoints; mixed-measures ANOVA with adherence as a between-subjects factor. Cohen's d reported for effect size.
Outcome-by-outcome breakdown
Each percentage is the change in the mean instrument score from pre-treatment (Day 1) to post-treatment (Day 22), calculated as (post − pre) ÷ pre × 100. For symptom scales (BDI-II, BAI, Sleep Quality Questionnaire) lower scores mean less symptom burden, so a reduction is clinically positive. For quality-of-life scales (WHOQOL-BREF) higher scores are better, so an increase is positive. Cohen's d is the standardized effect size — the more rigorous statistical measure.
Improved
Sleep Quality
Score change
0%
Pre → Post
18.44 → 11.24
Significance
p < 0.001
Effect size
d = 0.89
Large effect
Mean Sleep Quality Questionnaire score (lower = better) dropped 39%. Most of that drop landed by Day 11 — earlier than the protocol predicted.
Reduced
Depression
Score change
0%
Pre → Post
12.03 → 6.82
Significance
p < 0.001
Effect size
d = 0.66
Medium-to-large effect
Mean BDI-II symptom score dropped 43%, moving the group from the mild range (12.03) into the minimal range (6.82).
Improved
Physical Quality of Life
Score change
0%
Pre → Post
26.41 → 28.91
Significance
p = 0.002
Effect size
d = 0.63
Medium-to-large effect
Mean WHOQOL-BREF physical-health domain score (higher = better) rose 9% — energy, sleep, daily function.
Reduced
Anxiety
Score change
0%
Pre → Post
8.88 → 6.41
Significance
p = 0.027
Effect size
d = 0.36
Small-to-medium effect
Mean BAI symptom score dropped 28% — a meaningful but smaller effect than depression or sleep.
Improved
Psychological Quality of Life
Score change
0%
Pre → Post
20.52 → 21.76
Significance
p < 0.05
Effect size
d = 0.32
Small-to-medium effect
Mean WHOQOL-BREF psychological domain score (higher = better) rose 6% — mood, self-image, concentration.
Where Bio-Tuning did not show a significant effect
Most of the sleep benefit landed before the protocol said it would.
The Center for Neuroacoustic Research had long taught that Bio-Tuning effects emerge gradually over a 21-day exposure window. Santillan added a midpoint measurement to test that assumption.
The repeated-measures analysis on sleep quality found:
Day 1 (baseline)
17.94
Day 11 (mid)
11.45
d = 0.83 vs baseline
Day 22 (post)
10.36
not significantly different from Day 11
"The Center for Neuroacoustic Research previously reported 21 days as the time needed for improvements to occur; however, the current study shows improvement occurring much earlier… Bio-tuning practitioners may consider reducing their 21-day use recommendation so that it is aligned with the results of this study. Indeed, if the improvement is immediate, Bio-tuning may also be considered for the treatment of severe psychiatric experiences, such as a major depressive episode."
— Santillan (2022), Discussion section
"In this study… participants reported an improvement in symptoms of depression and anxiety. Additionally, participants reported a significant improvement in their quality of life, specifically in the domains of perceived physical and psychological health status, as well as an improvement in sleep quality… The present findings show that brainwave entrainment, and more specifically Bio-tuning, may be effective as a tool for stress reduction."
"This study is the first of its kind to be conducted outside of any internal ties to the company that could be misconstrued as a conflict of interest. As such, these results provide an objective evaluation of the Bio-tuning protocol that support its implementation across a wider range of clinical environments."
— Santillan (2022)
Read the Full Paper
Every number on this page is in the dissertation.
The full text — including methods, statistical tables, and the author's complete discussion — is open access through the American Journal of Biomedical Science & Research.
Read the full study