Bipolar disorder
Bipolar disorder (also known as manic depression) is a mental illness where a person will have repeated, long-lasting feelings (episodes) of high (mania) and low mood (depression). It may occur with or without cycles of normal mood, called euthymia. A mixed episode occurs when both mania and depression are present at the same time. People with bipolar disorder experience the whole spectrum of emotional feelings from unimaginable grief to full blown euphoria whereas normal people experience only a section of the spectrum of emotional feelings somewhere between extreme grief and extreme happiness.