Mania, also known as manic syndrome, is a mental and behavioral disorder defined as a state of abnormally elevated arousal, affect, and energy level, or "a state of heightened overall activation with enhanced affective expression together with lability of affect." During a manic episode, an individual will experience rapidly changing emotions and moods, highly influenced by surrounding stimuli. Although mania is often conceived as a "mirror image" to depression, the heightened mood can be either euphoric or dysphoric. As the mania intensifies, irritability can be more pronounced and result in anxiety or anger.

The symptoms of mania include elevated mood (either euphoric or irritable), flight of ideas and pressure of speech, increased energy, decreased need and desire for sleep, and hyperactivity. They are most plainly evident in fully developed hypomanic states. However, in full-blown mania, these symptoms become progressively exacerbated. In severe manic episodes, these symptoms may be obscured by other signs and symptoms characteristic of psychosis, such as delusions, hallucinations, fragmentation of behavior, and catatonia.