This approach attempts to understand behaviors and experiences in terms of biological structures and functions. In fact, the basis of behavior lies in the biological system of the organism. The behaviors not only emanate form the biological system, but they also influence the system itself. This approach analyzes behaviour at the molecular level in physical terms. In this approach, environmental influences are recognized, but the biological processes are considered more important.

The biological approach studies brain processes, nervous system, functions of glands, genetic basis of behavior, biochemical and neural processes, role of instincts, and the influence of heredity. Simple and even complex forms of behaviors are considered to have critical biological components. The researchers use a variety of methods to study brain functions and the causes of abnormal behavior.

The biological approach, because of its precise and objective methods of investigation, has broad appeal. The methods adopted closely resemble those in natural sciences. This approach has made major contributions in treating people with severe mental disorders.