S–T

seasonal affective disorder (SAD) DEPRESSION
that develops during the winter months when the
hours of darkness exceed the hours of daylight.
Researchers believe a key factor in SAD is an
increase in the amount of MELATONINthe PITUITARY
GLANDproduces. Melatonin is a HORMONEthat reg-
ulates the body’s circadian cycle (wake and sleep
pattern). Darkness stimulates melatonin release.
Higher than normal levels of melatonin cause
tiredness and reduce energy. Bright light causes
the pituitary gland to back off melatonin produc-
tion, causing wakefulness and alertness. Another
factor may be the level of serotonin, a NEUROTRANS-
MITTERassociated with mood, in the BRAIN.
Symptoms of SAD commonly appear each year
during the winter months and include

• profound lethargy


• disinterest in life


• tiredness or urge to sleep


• craving for sweets (simple carbohydrates)


• weight gain

The most effective treatment for SAD is expo-
sure to bright light, ideally sunlight outdoors.
Walking an hour a day in the winter often dra-
matically improves symptoms, likely a combina-
tion effect of the exposure to light and exercise.
Arranging one’s workspace to have as much natu-
ral light as possible (or using light bulbs that emu-
late daylight) is often helpful for people who
cannot get outdoors during daylight hours. Symp-
toms cause significant enough dysfunction in
some people to warrant therapy with ANTIDEPRES-
SANT MEDICATIONS, typically selective serotonin
reuptake inhibitors (SSRIs) to increase serotonin
levels in the brain.

See also EXERCISE AND HEALTH RISK REDUCTION;

POSTPARTUM DEPRESSION; SLEEP DISORDERS; WALKING

FOR FITNESS; WEIGHT LOSS AND WEIGHT MANAGEMENT.

schizophrenia A serious psychotic disorder with

marked emotional, cognitive, and physical symp-

toms. Schizophrenia represents a profound and

disabling break from reality. Researchers do not

know what causes schizophrenia, though it tends

to run in families, which suggests a genetic foun-

dation is likely. Differences in BRAINstructure in

people who have schizophrenia, apparent with

diagnostic imaging, also suggest organic factors

that likely affect the ways the brain receives,

organizes, and processes information. Symptoms

in men often begin in late ADOLESCENCEor early

adulthood; symptoms in women tend to develop

in early to middle adulthood. More than three

million Americans have schizophrenia.

Symptoms and Diagnostic Path

There are five types of schizophrenia—catatonic,

disorganized, paranoid, undifferentiated, and

residual—that share many common symptoms as

well as have unique symptoms. These symptoms

must be continuous six months or longer and rep-

resent a dramatic and observable deterioration

in function. Symptoms common to all types of

schizophrenia, though present to differing degrees

in different types, include

• DELUSION(untrue belief)


• HALLUCINATION(false sensory perception)


• chaotic or disordered thought processes and
  expression of ideas


• bizarre behavior and involuntary movement

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