The diathesis-stress model is a psychological theory that explains behavior as both a result of biological and genetic factors ("nature"), and life experiences ("nurture"). This theory is often used to describe the pronunciation of mental disorders, like schizophrenia, that are produced by the interaction of a vulnerable hereditary predisposition, with precipitating events in the environment.
In the diathesis-stress model, an inborn and genetic vulnerability or predisposition (diathesis) interacts with the environment and life events (stressors) to trigger behaviours or psychological disorders. The greater the underlying vulnerability, the less stress is needed to trigger the behaviour/disorder. Conversely, where there is a smaller genetic contribution greater life stress is required to produce the particular result.