The first public health applications of psychology were strongly focused on risk perception and risk taking. The best example may be the health belief model, where the perception of the severity of the risk and the susceptibility for the risk were seen as the primary determinants of health-protective behaviors. Over time, it became clear that people have many reasons for health-related behaviors, of which risk perception is often not an important one. In this multicausality approach, there is also a growing recognition of the many psychosocial and environmental influences on individual behavior. Changes in psychosocial determinants (e.g., self-efficacy) are most effective in creating behavior change when paralleled by changes in the social and physical environment(e.g., removal of barriers).

The application of psychological theories to public health is not without debate. Some professionals state that psychological theories will never be able to fully help us understand behavior and behavior change; other professionals claim that in practice there is nothing so helpful as a good theory. Both perspectives are justified. Theories are, by definition, a reduction of reality, but they do help people organize their thoughts and ask the right questions. The interesting contribution of theories is that they can generalize findings from one area of behavior to be of use in another.