Altering Default Mode Network Activity With Transcranial Focused Ultrasound to Reduce Depressive Symptoms

Participants will first complete the online screening to identify those who may meet criteria of major depressive disorder and have high RNT. Those meeting these criteria will be contacted for a formal diagnostic interview, consisting of the consent process and a structured clinical interview using the DSM-5. Once deemed eligible, participants will complete baseline interviews, self-report surveys, and an MRI session. Then, they will complete up to three weeks of ultrasound treatment, wherein the first week consists of five ultrasound sessions. Upon completion of week one, participants will complete the same interview, self-report surveys, and MRI session. Participants' symptom improvement will be determined by whether they meet remission criteria, defined as a Beck Depression Inventory Score - II (BDI-II) of \<13 and a Hamilton Depression Rating Scale (HDRS) score of \<8. If remission criteria are not met, participants will continue ultrasound sessions for two more weeks, three sessions per week. Following completion, participants will complete a final interview, self-report surveys, and MRI session. In each treatment session, the ultrasound device will be placed on the participants' forehead with the aid of the customized headset co-localized to the participant's structural MR image. Each ultrasound treatment lasts ten minutes.