Both MM and CBT interventions are patterned after established programs, adapted to meet the needs of patients with opioid-treated CLBP, with input from content experts and patient partners. The manualized interventions will be delivered by trained therapists over 8 weeks in weekly two-hour group sessions in addition to care the participants are already receiving from their regular clinicians; participants will also be asked to practice MM or CBT strategies at home during the entire study (at least 30 minutes/day, 6 days/week).