Bipolar disorder
Bipolar disorder or bipolar affective
Affect (psychology)
Affect refers to the experience of feeling or emotion. Affect is a key part of the process of an organism's interaction with stimuli. The word also refers sometimes to affect display, which is "a facial, vocal, or gestural behavior that serves as an indicator of affect" .The affective domain...

, historically known as manic–depressive disorder, is a psychiatric diagnosis
Classification of mental disorders
The classification of mental disorders, also known as psychiatric nosology or taxonomy, is a key aspect of psychiatry and other mental health professions and an important issue for consumers and providers of mental health services...

 that describes a category of mood disorders defined by the presence of one or more episodes of abnormally elevated energy levels, cognition
In science, cognition refers to mental processes. These processes include attention, remembering, producing and understanding language, solving problems, and making decisions. Cognition is studied in various disciplines such as psychology, philosophy, linguistics, and computer science...

, and mood
Mood (psychology)
A mood is a relatively long lasting emotional state. Moods differ from emotions in that they are less specific, less intense, and less likely to be triggered by a particular stimulus or event....

 with or without one or more depressive episodes. The elevated moods are clinically referred to as mania
Mania, the presence of which is a criterion for certain psychiatric diagnoses, is a state of abnormally elevated or irritable mood, arousal, and/ or energy levels. In a sense, it is the opposite of depression...

 or, if milder, hypomania
Hypomania is a mood state characterized by persistent and pervasive elevated or irritable mood, as well as thoughts and behaviors that are consistent with such a mood state...

. Individuals who experience manic episodes also commonly experience depressive
Major depressive episode
A major depressive episode is the cluster of symptoms of major depressive disorder. The description has been formalised in psychiatric diagnostic criteria such as the DSM-IV and ICD-10, and is characterized by severe, highly persistent depression, and a loss of interest or pleasure in everyday...

 episodes, or symptoms, or a mixed state
Mixed state (psychiatry)
In the context of mental disorder, a mixed state is a condition during which symptoms of mania and depression occur simultaneously...

 in which features of both mania and depression are present at the same time.