Which characteristic is associated specifically with Bipolar I disorder?

A defining characteristic of Bipolar I disorder is the occurrence of at least one manic episode. This manic episode is typically severe and can significantly impact an individual's daily functioning, often requiring hospitalization to prevent harm to themselves or others. In addition to the manic episode, a person with Bipolar I disorder can also experience depressive episodes, but these are not necessary for the diagnosis.

The manic episodes in Bipolar I disorder are characterized by elevated mood, increased energy, and often impulsive or risky behavior. This distinguishes it from other mood disorders, such as Bipolar II disorder, where the individual experiences hypomanic episodes that are less severe than full-blown manic episodes.

While frequent mixed episodes, which involve symptoms of both mania and depression occurring simultaneously, can happen in Bipolar I, they are not a defining characteristic. Additionally, persistent depressive episodes are more commonly associated with unipolar depression rather than specifically with Bipolar I disorder. Therefore, the presence of at least one manic episode is what specifically characterizes Bipolar I disorder.