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.