Which diagnosis requires at least one manic episode at some point in a person's life?

Bipolar I Disorder requires at least one manic episode in a person's lifetime for diagnosis. A manic episode is characterized by a distinct period of abnormally elevated, expansive, or irritable mood, lasting at least one week (or any duration if hospitalization is necessary) and accompanied by additional symptoms such as increased energy or activity, decreased need for sleep, racing thoughts, distractibility, and risky behaviors.

In this context, the presence of at least one manic episode is crucial because it differentiates Bipolar I Disorder from other mood disorders, such as Bipolar II Disorder, which involves hypomanic episodes rather than full manic episodes, and Cyclothymic Disorder, which entails numerous periods of hypomanic symptoms alongside depressive symptoms but does not meet the criteria for full episodes. Major Depressive Disorder, on the other hand, requires the presence of depressive episodes but does not involve manic or hypomanic episodes at all. Therefore, the stipulation of a manic episode is what firmly establishes the diagnosis of Bipolar I Disorder within the DSM-5 framework.