About Volunteer Comprehensive Treatment Center in Chattanooga, TN Volunteer Comprehensive Treatment Center (CTC) serves adults in the Chattanooga, Tennessee, area who need outpatient care for opioid addiction. Our center provides medication-assisted treatment (MAT) for adults age 18 and older of all genders who have been struggling with addictions to heroin, prescription pain pills, and other opioids. MAT has been used in methadone clinics in the U.S. for decades, and it has proved to be an extremely effective means of helping adults achieve recovery from opioid addiction.