Signs and symptoms
Mania is the defining feature of bipolar disorder,[7] and can occur with different levels of severity. With milder levels of mania, known as hypomania, individuals appear energetic, excitable, and may be highly productive.[8] As mania worsens, individuals begin to exhibit erratic and impulsive behavior, often making poor decisions due to unrealistic ideas about the future, and sleep very little.[8] At the most severe level, manic individuals can experience very distorted beliefs about the world known as psychosis.[8] A depressive episode commonly follows an episode of mania.[8] The biological mechanisms responsible for switching from a manic or hypomanic episode to a depressive episode or vice versa remain poorly understood.[9]