Psychology is an academic and applied field relating the study of the human mind, brain, and behavior. Psychology also refers to the application of such knowledge to various spheres of human activity, including problems of individuals' daily lives and the handling of mental illness.

Psychology differs from anthropology, economics, political science, and sociology in seeking to capture explanatory generalizations regarding the mental function and overt behavior of individuals, while the other disciplines rely more deeply on field studies and historical methods for extracting descriptive generalizations. In practice, however, there is relatively a lot of cross-fertilization that takes place among the various fields. Psychology differs from biology and neuroscience in that it is mostly concerned with the interaction of mental processes and behavior, and of the overall processes of a system, and not simply the biological or neural processes themselves, though the subfield of neurophysiology combines the study of the actual neural processes with the study of the mental effects they have subjectively formed

Research psychology
Research psychology encompasses the study of behavior for application in academic settings, and contains numerous areas. It contains the areas of abnormal psychology, biological psychology, cognitive psychology, comparative psychology, developmental psychology, personality psychology and social psychology. Research psychology is contrasted with applied psychology.

Abnormal psychology
Abnormal psychology is the study of abnormal psychological behavior in order to describe, predict, explain, and change abnormal patterns of performance. Abnormal psychology studies the nature of psychopathology and its causes, and this knowledge is useful to treating patients with psychological disorders in clinical psychology.

The Diagnostic and Statistical Manual of Mental Disorders, published by the American Psychiatric Association, is the handbook used most often in diagnosing mental disorders in the United States. The present version of the book is known as DSM IV-TR. It lists a set of disorders and provides complete descriptions on what constitutes a disorder, such as Major Depression or Anxiety Disorder.