The types of functional mental health disorders include schizophrenia, bipolar disorder, and major depressive disorder. Mania is a state of abnormally elevated, expansive, or irritable mood, often accompanied by increased energy, decreased need for sleep, racing thoughts, and impulsive behavior. In contrast, depression is characterized by a persistently low mood, loss of interest or pleasure in activities, low energy, feelings of worthlessness or guilt, and disturbances in sleep and appetite.