A Mixed Episode is characterized by a period of time (lasting at least 1 week) in which the criteria are met both for a Manic Episode and for a Major Depressive Episode nearly every day (Criterion A). The individual experiences rapidly alternating moods (sadness, irritability, euphoria) accompanied by symptoms of a Manic Episode and a Major Depressive Episode. The symptom presentation frequently includes agitation, insomnia, appetite dysregulation, psychotic features, and suicidal thinking. The disturbance must be sufficiently severe to cause marked impairment in social or occupational functioning or to require hospitalization, or it is characterized by the presence of psychotic features (Criterion B). The disturbance is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication, or other treatment) or a general medical condition (e.g., hyperthyroidism) (Criterion C).
Symptoms like those seen in a Mixed Episode may be due to the direct effects of antidepressant medication, electroconvulsive therapy, light therapy, or medication prescribed for other general medical conditions (e.g., corticosteroids). Such presentations are not considered Mixed Episodes and do not count toward a diagnosis of Bipolar I Disorder. For example, if a person with recurrent Major Depressive Disorder develops a mixed symptom picture during a course of antidepressant medication, the diagnosis of the episode is Substance-Induced Mood Disorder, With Mixed Features, and there is no switch from a diagnosis of Major Depressive Disorder to Bipolar I Disorder. Some evidence suggests that there may be a bipolar “diathesis” in individuals who develop mixed-like episodes following somatic treatment for depression. Such individuals may have an increased likelihood of future Manic, Mixed, or Hypomanic Episodes that are not related to substances or somatic treatments for depression. This may be an especially important consideration in childrn and adolescents.