Depression is a common psychiatric disorder in children, adolescents, adults, and the elderly. Primary care providers, not mental health professionals, treat the majority of patients with symptoms of depression. Persons who are depressed have feelings of sadness, loneliness, irritability, worthlessness, hopelessness, agitation, and guilt that may be accompanied by an array of physical symptoms as well as substance abuse. Identifying patients with depression and substance abuse can be difficult in busy primary care settings where time is limited, but certain depression/substance abuse screening tools may help diagnose the disorder. MN576 Psychiatric Disorder ; Depression Assignment Papers.