Substance use treatment; Treatment for co-occurring substance use plus either serious mental health illness in adults/serious emotional disturbance in children; Outpatient; Regular outpatient treatment; Does not treat alcohol use disorder; Does not treat opioid use disorders; Cognitive behavioral therapy; Substance use disorder counseling; Trauma-related counseling; Private for-profit organization; State Substance use treatment agency; State mental health department; State department of health; Federal military insurance (e.g., TRICARE); Private health insurance; Cash or self-payment; Clients with co-occurring mental and substance use disorders; Comprehensive substance use assessment; Screening for tobacco use; Screening for substance use; Screening for mental disorders; Aftercare/continuing care; Outcome follow-up after discharge; Treatment for gambling disorder; Treatment for other addiction disorder; Substance use disorder education; Smoking/vaping/tobacco cessation counseling; Individual counseling; Family counseling; Marital/couples counseling; Smoking not permitted; Children/adolescents; Female; Male; Specially designed program for DUI/DWI clients; Sign language services for the deaf and hard of hearing; Vaping not permitted; Mental health services; Social skills development; Suicide prevention services