Webster's New World Medical Dictionary

menstruation, cessation of
The ending of a
woman’s menstrual cycles. Menstruation ends natu-
rally in middle age with the onset of menopause. It
can also end suddenly as a result of induced
menopause. Cessation of menstruation in non-
menopausal women may be due to pregnancy, ill-
ness, disorders of the hypothalamus or pituitary
gland, medication, stress, overexercise, or malnu-
trition, among other causes. In particular, it can be
a symptom of anorexia, signaling potentially dan-
gerous changes in the body’s hormonal system.
Cessation of menstruation in women who have
established a regular menstrual cycle, or in girls or
teens who show other signs of anorexia, is a cause
for medical concern. Also known as amenhorrhea.
menstruation, retrograde
Menstruation in
which blood flows from the uterus into the Fallopian
tubes, and potentially into the abdomen. This con-
dition may play a role in the development of
endometriosis. See also 
endometriosis.
mental 1
Pertaining to the mind. 
2
Pertaining to
the chin.
mental child injury
See 
child abuse.
mental illness
Any disease that affects the cen-
tral nervous system, causing disturbances of thought
or behavior. Mental illnesses can be caused by
genetic, metabolic, structural, infectious, or envi-
ronmental causes. The term mental illness is also
used to describe emotional disturbances caused by
traumatic or distressing events or by poor adjust-
ment to normal life stresses. Treatment depends on
the root cause of the illness and may include use of
medication, surgery (as in the case of brain tumors
and some types of epilepsy), and various forms of
therapy to help rebuild life skills.
mental retardation
The condition of having an
IQ measured as below 70 to 75 and significant
delays or lacks in at least two areas of adaptive
skills. Mental retardation is present from childhood.
Between 2 and 3 percent of the general population
meet the criteria for mental retardation. Causes of