What are the symptoms of bipolar disorder, and at what age do they start to appear?

My girlfriend's mother was bipolar, and she is worried she might be as well. I haven't noticed anything, other than the fact that she has a dysfunctional family, which makes her depressed. But I'm not sure.

Can anyone enlighten me?
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oh wikipedia.com is a good one too!
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you head gets cold and your ass gets hott! but seriously, suicide?
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wikipedia ploxx
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On a depressing note, my cousin killed himself on Thursday due to his bipolar-ness
'never a victim,' the role model said,
bang-bang, the bad guy is dead,
always a rockstar on eMpty TV,
the lesson complete, now the child has needs.