Two major types of unipolar disorders described by the (APA, 2013) are major depressive disorder and persistent depressive disorder (PDD; dysthymia).
MDD is defined by one or more MDEs, but no history of manic or hypomanic episodes.
This means that nearly one in five Americans will meet the criteria for MDD during their lifetime.
The 12-month prevalence—the proportion of people who meet criteria for a disorder during a 12-month period—for PDD is approximately 0.5% (APA, 2013).
The mood disturbance must be present for one week or longer in mania (unless hospitalization is required) or four days or longer in hypomania.
Concurrently, at least three of the following symptoms must be present in the context of euphoric mood (or at least four in the context of irritable mood): Manic episodes are distinguished from hypomanic episodes by their duration and associated impairment; whereas manic episodes must last one week and are defined by a significant impairment in functioning, hypomanic episodes are shorter and not necessarily accompanied by impairment in functioning.
Bipolar II Disorder is characterized by single (or recurrent) hypomanic episodes and depressive episodes.
Another type of BD is cyclothymic disorder, characterized by numerous and alternating periods of hypomania and depression, lasting at least two years.
According to the fifth edition of the These symptoms cannot be caused by physiological effects of a substance or a general medical condition (e.g., hypothyroidism).
The core criterion for a manic or hypomanic episode is a distinct period of abnormally and persistently euphoric, expansive, or irritable mood and persistently increased goal-directed activity or energy.