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Irritability

Some people with this condition suffer from "mixed mania," where they experience symptoms of mania and depression at the same time. During this state, they are often extremely irritable.

Everyone has bad days, which is one reason this kind of bipolarity is much harder to recognize.

"We are all irritable or moody sometimes," Dr. Bearden says. "But in people with bipolar disorder it often becomes so severe that it interferes with their relationships—especially if the person is saying, 'I don’t know why I’m so irritable…I can’t control it.'"

Next: Rapid speech