Biomarkers for mental disorders: EEG frequency bands - Spectral changes in the resting-state EEG
Increase in delta and/or theta: ADHD, schizophrenia, OCD (Obsessive-Compulsive Disorder), depression, bipolar disorder, alcohol addiction.
"Only cases in the lower frequency bands where the dominant result was a decrease, rather than an increase, was for autism (eyes closed) and PTSD/early life stress (eyes open)."
ADHD* and the theta-beta ratio
Use of the ratio of the theta band (4-7 Hz) to the delta band (13-30 Hz) to assist ADHD diagnosis:
"Neuropsychiatric EEG-Based Assessment Aid for ADHD*" or NEBA System by NEBA Health
Approval of the device by the FDA and identification as "Neuropsychiatric Interpretive Electroencephalograph Assessment Aid"
Discussion on FDA device approval linked to FDA endorsement of the theta-beta ratio