There are other mood disorders besides depression. One that is less common is mania, in which the person becomes euphoric or “high”, extremely active, and excessively talkative, and easily distracted. People suffering from mania may also become grandiose – that is, their self-esteem is greatly inflated. They typically have unlimited hopes and schemes, but little interest in realistically carrying them out. People in a manic state sometimes become aggressive and hostile toward others as their self-confidence grows more and more exaggerated. At the extreme, people going through a manic episode may become wild, incomprehensible, or violent until they collapse from exhaustion.

Manic episodes rarely appear by themselves; rather, they usually alternate with depression. Such a mood disorder, in which both mania and depression are present, is known as bipolar disorder. In bipolar disorder, periods of mania alternate with periods of depression (each lasting a few days to a few months), sometimes with periods of normal mood intervening. Occasionaly, bipolar disorder is seen in a mild form: The person has alternating moods of unrealistically high spirits followed by moderate depression. Research indicates that bipolar differs in several ways from unipolar depression. Bipolar disorder is much less common and, unlike depression, which occurs two to three times more frequently in women than men, bipolar disorder is equally prevalent in men and women. Bipolar disorder also seems to have a stronger biological component than depression: It is more strongly linked to heredity and is more often treated by drugs.

Reference:

1. Understanding Psychology: 3^rd Edition. Charles G. Morris.