This study will test the hypotheses that adolescent with repetitive negative thinking who at at-risk for serious mental illness will show greater default mode network (DMN) connectivity than healthy controls, at-risk adolescents will show greater changes in DMN connectivity than healthy controls, and that a longer session of mindfulness based neurofeedback will lead to greater reduction in DMN connectivity. To do so, 50 adolescents with elevated repetitive negative thinking and 50 matched healthy control participants will be enrolled into a double-blind randomized clinical trial of a session of mindfulness training with either active mindfulness-basde neurofeedback or sham mindfulness-based neurofeedback.

A sample of 50 at-risk adolescents with elevated repetitive negative thinking and 50 matched healthy control participants, ages 13-21, will be enrolled into this double blind, randomized clinical trial. Healthy control participants will be matched for age and sex. All participants will complete a baseline clinical assessment and return within two weeks for a brief resting state MRI scan to assess default mode connectivity (DMN). At Visit 2, at-risk adolescents will then receive a 45-minute mindfulness training by clinically trained staff. After the mindfulness training, participants will be randomized in a 1:1 ratio to receive either active or sham neurofeedback. Participants and staff will remain blind to assignment. Participants will have fMRI scans for resting state functional connectivity before and after mindfulness practice. Participants will complete two doses (15 minutes per dose) of real or sham mbNF in the scanner. At-risk adolescents will also complete a follow-up clinical assessment at 4-weeks post-scan (Visit 3) and complete daily surveys for approximately four weeks from Visit 2 to Visit 3.

Inclusion Criteria:

• Ages 13-21, inclusive
• If <18 years old: Competent and willing to provide written informed assent AND have a parent/legal guardian who is competent and willing to provide written informed consent
• If age ≥18 years: Competent and willing to provide written informed consent
• Tanner puberty stage ≥3 (to minimize neuroendocrine variability)
• Able to understand study procedures, read, and write in English
• Access to a mobile device to complete daily surveys

Additional Inclusion Criteria for At-Risk Adolescents - Recurrent negative thinking, defined as PTQ/PTQ-C total score >30 with at least two items rated as 3 (Often) or 4 (Almost Always)

Additional Inclusion Criteria for Healthy Controls

-PTQ/PTQ-C total score <15, with zero items rated as 3 (Often) or 4 (Always)

Exclusion Criteria:

• Any of the following lifetime mental health disorders by DSM-V criteria: psychotic disorders, bipolar disorder, recurrent moderate or severe major depressive disorder, conduct disorder, developmental disorder (e.g., autism), post-traumatic stress disorder, or obsessive compulsive disorder
• Severe lifetime substance use disorder
• Unstable medical or neurologic condition as determined by study staff, history of epilepsy or seizure disorder, head injury, loss of consciousness >5 minutes by participant self-report
• MRI contraindications (i.e. presence of ferromagnetic implants, cardiac pacemaker or pacemaker wires, metallic particles in the body, vascular clips in the head or previous neurosurgery, prosthetic heart valves, magnetic dental implants claustrophobia).
• Visual, auditory, or cognitive impairment (IQ<80 based on the Wechsler Abbreviated Intelligence Scale (WASI)) that may make it difficult to participate.
• Any condition or situation that would, in the investigator's opinion, make it unlikely that the participant could adhere safely to the study protocol.
• Pregnancy: a negative pregnancy test is required at the time of enrollment for any individuals of childbearing potential
• Individuals who are under the legal protection of the government or state (Wards of the State)

Data from this study will be submitted to the National Institute of Mental Health Data Archive (NDA). NDA is a large database where de-identified study data from many NIH-funded studies are stored and managed. The final dataset to be shared will include demographic, clinical (diagnostic interviews, questionnaires), and neuroimaging (MRI and fMRI) data collected from at-risk adolescents and healthy controls. Sufficient data from this project to validate and replicate findings described in the aims will be shared. The study protocol will be published as a methods/protocol paper. We will also publish and maintain detailed neurofeedback experiment data (including stimuli, experiment scripts, and analysis scripts) on GitHub.

Scientific data will be available one year after the grant end date specified on the first Notice of Award. Scientific data included in published manuscripts will be available at the time of publication if the publication occurs before the end of the grant period. NDA will make decisions about how long to preserve the data.

To request access of the data, researchers will use the standard processes at NDA, and the NDA Data Access Committee will decide which requests to grant. The standard NDA data access process allows access for one year and is renewable.