The present study is a randomized controlled trial comparing the efficacy and acceptability of CBT and MBCT group-based interventions adapted for young people at elevated risk for mood or psychotic disorder onset or relapse. Young people (ages 13-24) are provided with targeted psychoeducation and learn a variety of coping skills and wellness practices for mood regulation and stress and distress management. Parents meet separately to learn the same skills and receive guidance in supporting their youth with skill development. The therapy is also augmented by a mobile phone application that supports regular symptom monitoring and skills practice.

Psychosocial interventions that improve emotional health and stability could have a dramatically favorable impact on individual suffering among adolescents and young adults at risk for severe mental illness, as well as their family members. Unfortunately, youth who are at risk for bipolar disorder or psychosis are treated with a wide variety of medications and therapies, with little evidence-based practice.

The main objective of this study is to investigate the comparative efficacy and acceptability of weekly outpatient group-based Mindfulness based Cognitive Therapy (MBCT) and Cognitive Behavioral Therapy (CBT) adapted for youth at elevated risk for serious or persistent mood disorders or psychosis. Consistent with the National Institute of Mental Health's shift towards common underlying mechanisms across diagnoses ("Research Domain Criteria, or RDoc; Sanislow et al., 2010), recruitment for this study is transdiagnostic, targeting a range of youth with difficulties with mood dysregulation and stress.

All randomized control trial (RCT) participants receive one of the two active treatments. The order of treatment groups has been randomized, with participants blinded to their treatment assignment. Five to 15 young participants of similar age (teen or young adult) comprise each group. Parents receive a parallel parent-only group that informs them of the content and skills presented to their offspring.

The investigators will assess emotion dysregulation, psychiatric symptoms, overall functioning, and quality of life at baseline, immediately following the 9-week treatment, and at follow-up (3 months after therapy ends).

Clinical symptoms, cognitions, mindfulness, emotion regulation, and well-being will be measured at baseline and each follow-up assessment. Both youth and young adults will participate in a follow-up assessment immediately after the intervention. Youth participants will participate in a second follow-up assessment 12 weeks post-treatment.

The main investigative hypotheses are that both the MBCT and CBT programs will be acceptable to the young participants and parents and associated with high satisfaction ratings. Additionally, the investigators anticipate that both MBCT and CBT will be associated with comparable improvements in mood, anxiety, and psychotic symptoms and social functioning from pretreatment to final follow-up. Finally, the investigators anticipate that increases in mindfulness and reductions in negative cognitions from pretreatment to post-treatment and follow-up will be correlated with improvements in the young participants' self-reported emotional dysregulation and attention.

The study aims to add to the body of knowledge on evidence-based interventions targeting mood and stress pathways for youth at risk for chronic or serious mental health challenges.

Inclusion Criteria:

- Patient meets criteria for having experienced a (past or present) disorder marked by clinically significant mood instability, depression, and/or psychotic features (i.e., diagnosed with a mood disorder, adjustment disorder with depressed mood, or psychotic disorder) OR they are at clinical high risk for psychosis

Exclusion Criteria:

• Patient's current severity of illness interferes with participation in a group treatment (e.g., preoccupied with internal stimuli)
• Patient has a current substance use disorder
• Patient has a pervasive developmental disorder or intellectual disability
• Patient cannot speak and read English sufficiently to allow for valid interpretation of a clinical assessment provided in English