Electroencephalographic Biomarkers of Deep Transcranial Magnetic Stimulation Treatment Response for Major Depressive Disorder in Older Adults: A Preliminary Study.

AIM: Major depressive disorder (MDD) in older adults can result in detrimental health consequences and often presents with resistance to antidepressant treatment. While Hesed-coil 4 (H4) and 7 have shown great promise in the treatment of MDD in older adults, not all participants will respond. Establishing biomarkers to predict individual treatment responses and to better understand how these coils work to treat MDD in older adults is essential. Resting-state electroencephalography (rsEEG), a cost-effective technique, has been previously used to identify response biomarkers to psychiatric treatments. This study therefore aims to identify rsEEG biomarkers of response to the H4 and H7 coils in older adults with MDD. METHODS: Twenty-one older adults with treatment-resistant MDD were randomly assigned to undergo 20 sessions of either H4 or H7 coils. rsEEG recordings were ascertained at baseline and posttreatment, along with the 24-item Hamilton Depression Scale (HDRS-24). RESULTS: Although none of the effects remained significant after correction, several preliminary biomarker patterns emerged. Higher baseline gamma power at Fp1 and F4 predicted a lower likelihood of treatment response. Investigation into treatment correlate signals revealed that decreases in alpha power at F4 and P3, and increases theta power at F7, were associated with greater improvement in HDRS-24 scores. CONCLUSION: This study identified preliminary rsEEG biomarkers of H4 and H7 coil response in older adults with MDD, providing initial proof-of-concept. Therefore, these findings can help guide hypothesis generation in future research. With larger sham-controlled trials needed for definitive characterization and validation.