Inclusion Criteria:
* Be between 22 and 80 years of age (inclusive) on the day of signing informed consent.
* Have at least one of the following at screening: PHQ-9 total score 5-16 (depression), GAD-7 total score 5-14 (anxiety), or OCI-R total score 14-27 (obsessive-compulsive disorder).
* If currently taking psychiatric medication, have been on the same stable dose(s) for at least 4 weeks prior to screening and be willing to maintain the regimen throughout the treatment period.
* Be able and willing to undergo a multi-sequence cranial MRI.
* Be willing to use the ATTN201 device during stimulation visits and to attempt use of monitoring devices (optional ambulatory EEG system, smart watch) during the pre- and post-stimulation monitoring blocks; use of the optional ambulatory EEG system does not affect eligibility.
* Sign the informed consent form, in accordance with local requirements, after the scope and nature of the investigation have been explained to the participant, and before any screening assessments.
* Be able to speak, read, and understand English.
* Be able to use a smartphone and the Attune platform.
* Possess the ability to respond verbally to questions, follow instructions, and complete study assessments.
* Be able to adhere to the treatment protocol and visit schedules through the 3-month post-treatment follow-up.
* Be judged by the investigator as likely to comply with study procedures and willing to participate in the entirety of the study.
* Be determined by the investigator to be medically stable at baseline as assessed by medical history and non-significant clinical results of a vital signs examination.
* Male participants must ensure a condom is used for all sexual intercourse and follow acceptable methods of contraception for their female partner for the entire duration of the study and for 90 days after the final study visit. Male participants should not father a child or donate sperm during this same period.
* Female participants who are sexually active agree to use two methods of contraception for the duration of the study and for 30 days after the final study visit, or not be of childbearing potential as indicated by natural menopause (≥12 consecutive months of spontaneous amenorrhea), hysterectomy, bilateral tubal ligation, bilateral oophorectomy (with or without hysterectomy) more than 6 weeks prior to screening, or a vasectomized partner with documented absence of sperm.
Exclusion Criteria:
* Columbia Suicide Severity Rating Scale (C-SSRS) score ≥ 3 (ideation with intent, with or without plan) at screening.
* Any suicide attempt within the past 12 months.
* Any change in psychiatric medication (start, stop, or dose change) within 4 weeks prior to screening.
* Has an unstable or severe medical or psychiatric condition that, in the investigator's judgment, would pose a safety risk to the participant or prevent completion of study procedures. Stable comorbid conditions (e.g., treated depression, anxiety, OCD, insomnia) within the protocol-specified score windows are permitted.
* Has an active, unstable substance use disorder including alcohol use disorder in the past 6 months (except for caffeine and nicotine). Participants on stable medication-assisted treatment (e.g., buprenorphine, methadone, naltrexone) for at least 6 months are eligible.
* Has a history of moderate-to-severe traumatic brain injury, or mild traumatic brain injury within the past 12 months.
* Has a history of seizure disorder or epilepsy, or any structural CNS lesion known to lower seizure threshold.
* Has any contraindications for completing a brain MRI scan (e.g., pacemaker, ferromagnetic implants).
* Body mass index (BMI) greater than 40 kg/m².
* Is pregnant, is attempting to become pregnant, or is nursing.
* Is or has an immediate family member (e.g., spouse, parent/legal guardian, sibling, or child) who is an investigational site or Sponsor staff member directly involved with this trial.
* Has a known allergy or sensitivity to ultrasound gel, silicone, or adhesive materials used in monitoring devices.
* Has an active skin condition at sensor placement sites that would prevent device wear.
* Has received an investigational drug or device in another clinical study within 30 days before screening
