(IOP) The Intensive Outpatient Program (IOP) is an intensive psychotherapeutic program designed to treat substance use disorders and co-occurring mental health disorders. Services include group therapy, individual counseling, and toxicology testing. Sessions are often done as a group. Clients go home each night, rather than living at a treatment center. Clients attend IOP groups 3-5 days per week, for a total of 9-15 hours per week.