This article is from the Bipolar Disorder FAQ, by firstname.lastname@example.org (Barry Campbell) with numerous contributions by others.
Hypomania means, literally, "mild mania."
It's sometimes difficult to draw a distinct line between "manic" and
"hypomanic," as "marked impairment" is a necessarily subjective evaluation.
Also, one of the reasons that bipolar disorder often has a delayed
diagnosis may be that hypomanic episodes are often overlooked amid
the "Sturm und Drang" of adolescense and early adulthood.
The associated features of mania are present in Hypomanic Episodes, except that
delusions are never present and all other symptoms are *generally* less severe
than they would be in Manic Episodes.
Criteria for Hypomanic Episode (DSM-IV, p. 338)
A. A distinct period of persistently elevated, expansive, or irritable mood,
lasting throughout at least 4 days, that is clearly different from the usual
B. During the period of mood disturbance, three (or more) of the following
symptoms have persisted (four if the mood is only irritable) and have been
present to a significant degree:
(1) inflated self-esteem or grandiosity
(2) decreased need for sleep (e.g., feels rested after only 3 hours of sleep)
(3) more talkative than usual or pressure to keep talking
(4) flight of ideas or subjective experience that thoughts are racing
(5) distractibility (i.e., attention too easily drawn to unimportant or
irrelevant external stimuli)
(6) increase in goal-directed activity (either socially, at work or school, or
sexually) or psychomotor agitation
(7) excessive involvement in pleasurable activities that have a high potential
for painful consequences (e.g., engaging in unrestrained buying sprees, sexual
indiscretions, or foolish business investments)
C. The episode is associated with an unequivocal change in functioning that is
uncharacteristic of the person when not symptomatic.
D. The disturbance in mood and the change in functioning are observable by
E. The episode is not severe enough to cause marked impairment in social or
occupational functioning, or to necessitate hospitalization, and there are no
F. The symptoms are not due to the direct physiological effects of a substance
(e.g., a drug of abuse, a medication, or other treatment) or a general medical
condition (e.g., hyperthyroidism).
Note: Hypomanic-like episodes that are clearly caused by somatic
antidepressant treatment (e.g., medication, electroconvulsive therapy, light
therapy) should not count toward a diagnosis of Bipolar II Disorder.