<P> The diathesis--stress model is a psychological theory that attempts to explain a disorder as the result of an interaction between a predispositional vulnerability and a stress caused by life experiences . The term diathesis derives from the Greek term (διάθεσις) for a predisposition, or vulnerability . A diathesis can take the form of genetic, psychological, biological, or situational factors . A large range of differences exists among individuals' vulnerabilities to the development of a disorder . </P> <P> The diathesis, or predisposition, interacts with the individual's subsequent stress response . Stress is a life event or series of events that disrupts a person's psychological equilibrium and may catalyze the development of a disorder . Thus the diathesis--stress model serves to explore how biological or genetic traits (diatheses) interact with environmental influences (stressors) to produce disorders such as depression, anxiety, or schizophrenia . </P>

The vulnerability-stress model of mental illness argues that