Hypomania is an abnormally elevated mood in which a person talks more, needs less sleep, is more quickly irritated and can also engage in impulsive behavior such as risky sex, according to the DSM-IV criteria.
Depression is an unusually sad mood that causes loss of interest in once-enjoyed activities and may or may not include suicidal thoughts, according to the National Institute of Mental Health (NIMH).
To merit a bipolar II diagnosis, a hypomanic state usually must last at least four days and be preceded or followed by a depressive episode, according to the DSM-IV criteria.
If the patient has had a manic state, where severe impulsive behavior and excessive talking may occur, then a bipolar II diagnosis usually will not apply.
Those who have bipolar II usually suffer some impairment to normal functioning during their mood swings but not to the severity those with bipolar I might experience.
Bipolar II disorder is a milder form of full-blown bipolar or manic depressive illness. People who have bipolar II suffer from mood swings ranging from depression to over-elation, medically known as hypomania.