Clinical and Health psychology deals with the understanding the changes in individual psychology and behaviour during various situations like health and illness. One such example is the consumption of alcohol and some other psychotics can cause addiction or reinforced behaviour and can affect both mental and physical health.
Clinical psychology is the branch of psychology concerned with the assessment and treatment of mental illness, abnormal behavior and psychiatric problems. Wilhelm Wundt defines clinical psychology as the study of individuals, by observation or experimentation, with the intention of promoting change.