🧠 Theta–Beta Ratio (TBR) in ADHD — Science, Strengths & Why It Sometimes Misleads
Theta–beta ratio (TBR) is one of the most talked-about EEG markers in ADHD diagnosis. Some call it “brain’s fingerprint of inattention,” while others argue it has led to over-diagnosis. The truth lies somewhere in between — TBR is useful, but only when used the right way.
🌩️ What Exactly Is TBR?
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Theta waves (4–8 Hz) → Seen during drowsiness, inattention, mind-wandering.
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Beta waves (13–30 Hz) → Associated with alertness, focus, cognitive effort.
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TBR = Theta power ÷ Beta power (usually measured at Cz or Fz electrode).
Higher TBR = lower cortical arousal, which was historically linked to ADHD-inattentive type.
✅ Where TBR Works Well
| Where It Helps | Why It Matters |
|---|---|
| Supports ADHD diagnosis when combined with clinical evaluation | Adds objectivity instead of relying only on symptoms reported by parents/teachers. |
| Predicts response to stimulants or neurofeedback therapy | High TBR often correlates with better response to methylphenidate and EEG neurofeedback. |
| Measures treatment progress | A decrease in TBR after neurofeedback, rTMS, or medication suggests improved cortical activation. |
| Useful in research & controlled lab settings | When age, alertness and EEG artifacts are controlled, TBR can show reliable group differences. |
❌ What Causes False or Misleading TBR?
TBR is not ADHD-specific. Many conditions increase or decrease this ratio — leading to false diagnoses if used alone.
| ⚠️ Factor | ⚠️ How It Misleads |
|---|---|
| Sleep deprivation, boredom, drowsiness during EEG | Increases theta → falsely high TBR. |
| Anxiety, stress, hyperarousal | Increases beta → artificially lowers TBR. |
| Depression, autism, learning disorders, epilepsy | May show high TBR despite no ADHD. |
| Medications (benzodiazepines, antipsychotics, sedatives) | Alter brain rhythms, making TBR unreliable. |
| Eye blinks, muscle tension, poor electrode contact | Create artefacts mistaken for true theta/beta activity. |
| Age-related changes | TBR is naturally higher in children and drops with age → using one cutoff for all ages is inaccurate. |
| Using TBR as the only diagnostic test | ADHD is heterogeneous. Only ~30–40% of ADHD cases show high TBR. |
🧬 What Do Recent Studies Say?
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Early 2000s: TBR was considered a strong biomarker for ADHD.
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Post-2015 research shows mixed results.
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Large datasets (Loo et al. 2013, Arns 2018) show sensitivity ~60–70% and specificity ~50–60%.
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FDA-approved NEBA test allows TBR use only as a confirmatory tool, not a diagnostic replacement.
🎯 So How Should We Use TBR in 2025?
✅ Right way:
✔ Combine with DSM-5/ICD-11 clinical evaluation
✔ Add behavioral tests like CPT, QbTest, MOXO-CPT
✔ Rule out sleep deprivation, anxiety, autism, depression
✔ Use TBR to plan neurofeedback / rTMS protocols
✔ Track before–after treatment changes, not label people
❌ Wrong way:
✖ Diagnosing ADHD using only EEG values
✖ Ignoring sleep, medication or emotional state during EEG
✖ Using one cut-off value for all ages and populations
🔭 The Future – Moving Beyond Single Biomarkers
The future of ADHD evaluation is multi-modal, data-driven and personalized.
🧬 EEG + fNIRS (prefrontal oxygenation)
🎧 QbTest / MOXO reaction time variability
📊 AI-based machine learning models
📡 Digital phenotyping (actigraphy, heart rate variability)
🧪 Blood-based inflammatory/genetic markers (research phase)
TBR will remain useful — but only as one piece in a much larger puzzle.
✨ Author
🩺 Dr. Srinivas Rajkumar T
MD (AIIMS New Delhi), DNB, MBA (BITS Pilani)
Consultant Psychiatrist – Mind & Memory Clinic
Apollo Clinic (Opp. Phoenix MarketCity), Velachery, Chennai
📞 +91-8595155808
🌐 www.srinivasaiims.com