Substance use treatment; Treatment for co-occurring substance use plus either serious mental health illness in adults/serious emotional disturbance in children; Outpatient; Intensive outpatient treatment; Outpatient methadone/buprenorphine or naltrexone treatment; Regular outpatient treatment; Methadone used in Treatment; Buprenorphine used in Treatment; Naltrexone used in Treatment; Does not treat alcohol use disorder; Buprenorphine maintenance; Buprenorphine maintenance for predetermined time; Federally-certified Opioid Treatment Program; Methadone maintenance; Methadone maintenance for predetermined time; Methadone; Buprenorphine with naloxone; Buprenorphine without naloxone; Naltrexone (oral); Naltrexone (extended-release, injectable); Brief intervention; Cognitive behavioral therapy; Contingency management/motivational incentives; Motivational interviewing; Matrix Model; Relapse prevention; Substance use disorder counseling; Telemedicine/telehealth therapy; Trauma-related counseling; Private for-profit organization; State Substance use treatment agency; State department of health; Commission on Accreditation of Rehabilitation Facilities (CARF); SAMHSA certification for opioid treatment program (OTP); Drug Enforcement Agency (DEA); Private health insurance; Cash or self-payment; State-financed health insurance plan other than Medicaid; Pregnant/postpartum women; Clients with co-occurring mental and substance use disorders; Comprehensive mental health assessment; Comprehensive substance use assessment; Interim services for clients; Outreach to persons in the community; Complete medical history/physical exam; Screening for tobacco use; Screening for substance use; Screening for mental disorders; Breathalyzer or blood alcohol testing; Drug and alcohol oral fluid testing; Drug or alcohol urine screening; TB screening; Aftercare/continuing care; Discharge Planning; Naloxone and overdose education; Outcome follow-up after discharge; Self-help groups; Housing services; Mentoring/peer support; HIV or AIDS education, counseling, or support; Substance use disorder education; Individual counseling; Group counseling; Smoking permitted in designated area; Adults; Young adults; Female; Male; Opioid use disorder clients only; Other languages (excluding Spanish); Hmong; Vaping permitted in designated area; Case management service; Mental health services; Social skills development