In the diathesis-stress model, a biological or genetic vulnerability or predisposition (diathesis) interacts with the environment and life events (stressors) to trigger behaviors or psychological disorders. The greater the underlying vulnerability, the less stress is needed to trigger the behavior/disorder. Conversely, where there is a smaller genetic contribution greater life stress is required to produce the particular result. Even so, someone with a diathesis towards a disorder does not necessarily mean they will ever develop the disorder. Both the diathesis and the stress are required for this to happen.
The diathesis-stress model has been reformulated in the last 20 years as the stress-vulnerability-protective factors model, particularly by Dr. Robert P. Liberman and his colleagues in the field of psychiatric rehabilitation.
This model has had profound benefits for people with severe and persistent mental illnesses. It has stimulated research on the common stressors that people with disorders such as schizophrenia experience. More importantly, it has stimulated research and treatment on how to mitigate this stress, and therefore reduce the expression of the diathesis, by developing protective factors. Protective factors include rigorous and nuanced psychopharmacology, skill building (especially problem solving and basic communication skills) and the development of support systems for individuals with these illnesses. Even more importantly, the stress-vulnerability-protective factors model has allowed mental health workers, family members, and clients to create a sophisticated personal profile of what happens when the person is doing poorly (the diathesis), what hurts (the stressors), and what helps (the protective factors). This has resulted in more humane, effective, efficient, and empowering treatment interventions.