If you hear the way people throw the word around in casual conversation, you might think that "bipolar" just means being someone who experiences some pretty typical mood swings ("My mom was so mad at me last week, but now she's acting nice! She's acting bipolar"). But bipolar disorder is a real mental illness — one that impacts 5.7 million American adults every year, according to the International Bipolar Foundation. And when people with bipolar disorder ignore the signs and forgo treatment — either due to fear of stigma, or simply because they don't know that they have it — the disorder can make their lives incredibly hard.