Bipolar disorder is characterized by recurrent (at least two) episodes of markedly disturbed mood and activity levels, with the disorder sometimes manifesting as elevated mood, increased energy and activity (mania or hypomania), and sometimes as depressed mood, decreased energy and reduced activity (depression and mild depression). The interictal period usually resolves or largely resolves. However, it should be noted that it is not uncommon for depressive states of mind to be accompanied by hyperactivity and verbal urgency for several days to weeks, as well as manic states of mind and exaggerated states with decreased agitation, energy and initiative. Depressive symptoms and hypomanic or manic symptoms can also switch rapidly, even varying from day to day. The diagnosis of mixed bipolar disorder should be made if both sets of symptoms are prominent most of the time during the current episode of illness and the episode lasts at least 2 weeks.