Mindful Breathing and tDCS for Depression

This study will investigate whether transcranial direct current stimulation (tDCS) targeting the dorsolateral prefrontal cortex (DLPFC) can enhance the therapeutic effect of mindful breathing training (MBT) for adolescent depression. The objective is to enhance connectivity between the DLPFC with the amygdala and Default Mode Network (DMN) circuits as well as to enhance emotion regulation abilities and decrease rumination to reduce symptoms of depression. This will aid in the development of novel treatments for depression.

Aim 1: To demonstrate the feasibility of recruiting and randomizing adolescents with depression to a research protocol involving MBT and tDCS. The investigators expect that adolescents will be willing to enroll in a randomized trial involving MBT and tDCS.

Aim 2: To test the tolerability of MBT and tDCS in adolescents. The investigators expect that MBT will be well-tolerated and that active tDCS will show no difference in tolerance compared to sham stimulation.

Aim 3: To examine whether tDCS can enhance the effects of MBT. The investigators expect the MBT + tDCS group will show greater reduction in depressive symptoms compared to the MBT + sham stimulation group.

Aim 4: To examine the mechanisms of MBT +/- tDCS treatment. The investigators expect that depression symptom improvement will be associated with decreased rumination, improvements in emotion regulation, increased task-based and resting state DLPFC-DMN and DLPFC-amygdala connectivity, as well as increased DLPFC activation and reduced amygdala activation during rumination and emotion processing tasks. The investigators also expect reduced alpha asymmetry and reduced LPP amplitude during emotion regulation and emotion processing. The investigators expect these changes will be greatest in the active tDCS + MBT group.

Eligibility Criteria:
Inclusion Criteria:

* Diagnosis of major depressive disorder (MDD), Dysthymia, or Other specified/Unspecified Depressive Disorder based on MINI.
* Experiencing current symptoms of depression as indexed by a MADRS-S score ≥ 13
* Ability to access the MBT online-based application (e.g., on a personal laptop, tablet, or cell phone)
* Fluent in English

Exclusion Criteria:

* Any participant with a clinically defined neurological disorder or insult including, but not limited to, a condition likely to increase the risk of seizure; such as, space occupying brain lesion; any history of seizure; history of cerebrovascular accident; transient ischemic attack within two years; cerebral aneurysm; dementia; brain surgery; history or stroke or family history of epilepsy
* Any participant with an increased risk of seizure for any reason, including prior diagnosis of increased intracranial pressure or history of significant head trauma with loss of consciousness for ≥ 5 minutes
* Participants with conductive, ferromagnetic, or other magnetic-sensitive metals implanted in the head excluding the mouth that cannot safely be removed. Examples include cochlear implants, implanted electrodes/stimulators, aneurysm clips or coils, stents, bullet fragments, jewelry and hair barrettes
* Participants with active or inactive implants (including device leads), including deep brain stimulators, cochlear implants, and vagus nerve stimulators
* Participants with pre-existing sores or lesions at the site of tDCS or EEG electrode placement
* A hair style that would impede EEG and tDCS electrode contact (e.g., dread locks)
* Any participant with a current or possibility of current pregnancy
* Participants unable to give informed consent.
* Participation in any investigational drug trial within 4 weeks of the baseline visit
* Clinically significant laboratory abnormality or medical condition, that in the opinion of the investigator would hinder the participant in completing the procedures required by the study
* Currently actively suicidal with intent and plan determined by the C-SSRS at the baseline visit.
* A diagnosis of current or recent substance use disorder (within the past 12 months)
* A diagnosis of Schizophrenia, Bipolar Disorder, or Autism
* Unstable psychotherapy (therapy must be for at least 3 months prior to entry into the study, with no anticipation of change in the frequency or treatment focus of the therapeutic sessions over the duration of the study)
* Recent change in dose of antidepressant medication (within 6 weeks prior to entry into the study). This includes all antidepressants and any adjunctive psychotropic medications that are being used to address problems related to mood or anxiety (e.g. antipsychotic medications, mood stabilizers)
* Refusal to cooperate with study procedures