bipolar who gets it

My sister gets very angry at the drop of a hat, she is bipolar?
My sister reacts whenever it gets very unhappy and angry, suddenly. Could that be bipolar? This happens on a regular day is obviously upset about the smallest things (like I did not want to watch a movie with her).
During a manic episode of bipolar disorder is not uncommon for someone to show anger and even rage, however, the situation of his sister, does not sound as a manic episode of bipolar disorder, since you say this happens on a normal day-to-day. Bipolar disorder is more "episodes", with periods normal in the middle. The average person will only have about four episodes per year. You gave your own answer when you said your sister "overreact" whenever you are dissatisfied and gets very angry, suddenly. There is another condition called borderline personality disorder he has as a symptom, but if this is just an isolated symptom, could simply be a learned response and not a consequence of mental illness.
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