Mountainside Treatment Center, a renowned drug and alcohol rehabilitation center headquartered in Canaan, Connecticut, today announced that it has earned The Joint Commission’s Gold Seal of Approval accreditation for Behavioral Health Care and for Opioid Treatment. Mountainside Treatment Center, a renowned drug and alcohol rehabilitation center headquartered in Canaan, Connecticut, today announced that it has earned The Joint Commission’s Gold Seal of Approval accreditation for Behavioral Health Care and for Opioid Treatment.