Understanding maladaptive behaviour in human beings has a long history. However, formal introduction of abnormal psychology as a new branch of psychological inquiry dates back to Sigmund Freud’s discovery of the unconscious. As one of the most sophisticated and specialized branch of psychology, abnormal psychology seeks to describe, explain, predict, and control behaviours that are considered strange, maladaptive, or unusual. Its subject matter consists of studying a range of behaviours that depart from some norm, and harm the affected individual and others.

These behaviour anomalies range from simple adjustment problems, neurotic behaviour, anxiety problems, and socio-emotional disorientation to severe psychotic disorders of schizophrenia and manic-depressive psychosis. The purpose of abnormal psychology lies in the classification of various mental disorders, locating and explaining their etiology, preparing tests and instruments for their assessment, and finally, making provisions for treatment. Mental health problems are widespread in the contemporary societies. Therefore, abnormal psychology takes up a new assignment of prevention of mental disorder by planning out mental health programmes and counseling services.

Nowadays, psycho-physiological disorders are a major concern of the abnormal psychologists. Hypertension, asthma, peptic ulcer, migraine etc. are happening to people in a very large scale. Medical practitioners also try to find out a psychological root in almost every physical disease.