A paranoid person builds up an elabo-
rate set of beliefs based on the
interpretation of chance remarks or
events. Typical themes are persecution,
jealousy (see jealousy, morbid), love,
and grandeur.
Paranoia may be chronicor acute.
Chronic paranoia may be caused by
brain damage, abuse of alcohol or am-
fetamines, manic–depressive illness, or
schizophreniaand is likely in those with
a personality disorder. Acute paranoia,
lasting for less than 6 months, may
occur in people, such as refugees, who
have experienced radical changes. In
shared paranoia (see folie à deux), delu-
sion develops because of a close
relationship with someone else who
has a delusion.
There are usually no other symptoms
of mental illness apart from occasional
hallucinations. In time, anger, suspicion,
and social isolation may become severe.
If acute illness is treated early with
antipsychotic drugs, the outlook is good.
In longstanding paranoia, delusions are
usually firmly entrenched, but antipsy-
chotics may make them less prominent.
paraparesisPartial paralysisor weak-
ness of both legs and sometimes part of
the trunk.
paraphimosisConstriction of thepenis
behind the glans(head) by an extremely
tight foreskin that has been pulled back,
causing swelling and pain. Paraphim-
osis often occurs as a complication of
an abnormally tight foreskin (see phimo-
sis). The foreskin can often be returned
manually to its normal position after
application of an ice-pack. Otherwise,
an injection or an operation to cut the
foreskin may be necessary. Circumcision
prevents recurrence.
paraplegiaWeakness or paralysis of
both legs and sometimes of part of the
trunk, often accompanied by loss of
feeling and by loss of urinary control.
Paraplegia is a result of nerve damage
in the brainor spinal cord.
parapsychologyThe branch of psy-
chologydealing with experiences and
events that cannot be scientifically
accounted for. These include forms of
extrasensory perception (ESP), such as
telepathy (communication of thoughts),telekinesis (movement of objects with
the mind), and precognition (being able
to see into the future).
Many “paranormal” experiences can
probably be explained by mental distur-
bances; others are probably due to
coincidence, self-deception, or fraud.
paraquatA poisonous weedkiller that is
available in high concentrations for agri-
culturaluse and which can be fatal if
swallowed, inhaled, or absorbed through
the skin. Paraquat poisoning requires
urgent medical attention. The symptoms
may include breathing difficulties, mouth
ulcers, nosebleeds, diarrhoea, andlater,
respiratory and kidney failure. Treat-
ments include eating activated charcoal
or Fuller’s earth. Haemodialysismay
also be used.
parasiteAny organism living in or on
another living creature and deriving
advantage from it, while causing the
host disadvantage. The parasite obtains
food from the host’s blood, tissues, or
diet. Parasites may spend only part of
their life-cycles with the host or remain
there permanently. Some parasites cause
few symptoms, while others cause dis-
ease or even death.
Animal parasites of humans include
protozoa, worms, flukes,leeches, lice,
ticks, and mites. Virusesand disease-
causing fungi and bacteriaare also
essentially parasites.
parasitologyThe scientific study of
parasites. Although viruses and many
types of bacteria and fungi are para-
sites, their study is conducted under the
title of microbiology.
parasuicideSee suicide, attempted.
parasympathetic nervous system
One of the 2 divisions of the autonomic
nervous system.
parathionA highly poisonous agricul-
tural organophosphateinsecticide.
parathyroid glandsTwo pairs of oval,
pea-sized glands that lie behind the
thyroid glandin the neck. Some people
have only 1 parathyroid gland or have
extra glands in the neck or chest. The
glands produce parathyroid hormone,
which helps regulate the level of calci-
um in the blood; even small variations
in calcium level can impair muscle and
nerve function. Rarely, the parathyroidPARAPARESIS PARATHYROID GLANDSP