ACT groups were co-led by two therapists. Study therapists included two psychologists and one addictions counselor, each of whom had been conducting ACT groups with substance use disorder patients for at least 4 years and who had also led groups during the pilot project (Luoma et al., 2008). Therapists met before each wave of participants to review the manual and to rehearse the treatment. They debriefed difficult or ambiguous situations after sessions as they occurred.
