SMI - Serious Mental Illness - A condition experienced by persons 18 years of age and older who, at any time during the past year, had a diagnosable mental, behavioral, or emotional disorder that met the diagnostic criteria within the current DSM and that has resulted in functional impairment and which substantially interferes with or limits one or more major life activities. Adults who would have met functional impairment criteria during the referenced year without the benefit of treatment or other support services are considered to have serious mental illness. Substance use disorders and developmental disorders are not included.