Webster's New World Medical Dictionary

bipolar disorder
A disorder, formerly called
manic-depressive illness, in which the patient cycles
through uncontrollable mood states. Less prevalent
than simple clinical depression, bipolar disorders
involve cycles of depression, hypomania (elevated
mood), mania (extremely elevated mood), and in
some cases psychosis. Sometimes the mood
switches are dramatic and rapid, but most often they
are gradual. Both depression and mania affect
thinking, judgment, and social behavior in ways that
cause serious problems. For example, unwise busi-
ness, financial, and personal decisions may be
made when an individual is in a manic phase.
Bipolar disorder is usually a chronic recurring con-
dition, with serious impairment and suicide com-
mon in untreated cases. The cause is as yet
unknown, although bipolar disorders appear to
have a strong genetic basis and may be influenced
by seasonal patterns, hormones, or viral infection. A
strategy that combines medication and psychosocial
treatment is optimal for managing bipolar disease.
Also known as manic-depressive disease and manic
depression. See also 
cyclothymia; seasonal affec-
tive disorder; depression; mania; mixed mania.
birth
The process of delivering a fetus from the
uterus. Normally, the fetus is expelled through the
cervix and birth canal with the assistance of rhyth-
mic muscle contractions. Birth may instead be a
surgical procedure: a Caesarean section. See also
caesarean section.
birth control
The practice of exercising some
level of control over contraception. Birth control
methods are many, and they vary in effectiveness.
The most effective method is abstinence from sex,
followed by oral, injectible, or implanted contra-
ceptives; barrier methods used consistently and