What are different types of psychological diseases that you know?

Psychological diseases or disorders affect the way people
feel, think, speak, and behave. The field of psychology that deals with study and
treatment of such disorders is called abnormal
psychology.

What is considered normal and abnormal
behaviour differ from society to society and change as social conditions and customs
change.  For example, beating children to discipline them was considered normal and even
desirable behaviour in the past, but many people today consider such behaviour abnormal
and undesirable.

Psychological disorders may be classifies
in four groups according to theories that explain their likely causes and methods of
treatment. These are biophysical, intrapsychic, existential, and  behavioural.
Biophysical theories focus on underlying physical causes of psychological disturbances.
Such disorders are primarily treated with tranquillizers, antidepressants, sleeping
pills, and other drugs.  In a few cases electric shocks and surgery may also be used.
Most common disorders of this type are delirium and
dementia.

Intrapsychic theories focus on the emotional
basis of abnormal behaviour.  Such disorders may result from conflicts in early
childhood which may result in abnormal behavior can usually cope with everyday problems
are described as neurotics. Others with more severe problems causing individuals to lose
track of reality are called psychotic. Psychotic people may believe in very unrealistic
ideas called delusions, or may have hallucinations such as   "hearing voices" or "seeing
visions". This kind of disorders are often treated by psychoanalysis to help to help
them understand and resolve their conflicts and anxieties. Schizophrenia is the
commonest psychotic disorder in which a person suffers unpredictable disturbances in
thinking, mood, awareness, and behaviour. Depression (sadness) and mania (extreme joy
and over activity) also come under this category of disorders. People with bipolar
disorder suffer from alternating periods of depression and
mania.

Existential theories of abnormal behaviour stress
the importance of current experiences and the person's view of himself or herself. 
Treatment of such disorders involves helping patients gain insight into their feelings,
accept responsibility for their lives, and fulfil their
potential.

Behavioural theories emphasize the effects of
learning on behaviour.  Treatment based on behavioral theories attempt to change
abnormal behavior using a learning process called conditioning.  Thus people with such
disorders are treated by teaching them acceptable behaviour patterns and reinforcing
desired behaviour by rewards.