According to the diathesis-stress model of understanding abnormal behaviour, what is the diathesis component?

Biological aberrations that are inherited

One of the most widely accepted explanations of abnormal behaviour has been provided by the diathesis-stress model. This model states that psychological disorders develop when a diathesis (biological predisposition to the disorder) is set off by a stressful situation. This model has three components. The first is the diathesis or the presence of some biological aberration which may be inherited. The second component is that the diathesis may carry a vulnerability to develop a psychological disorder. This means that the person is ‘at risk’ or ‘predisposed’ to develop the disorder. The third component is the presence of pathogenic stressors, i.e. factors/ stressors that may lead to psychopathology. If such “at risk” persons are exposed to these stressors, their predisposition may actually evolve into a disorder. This model has been applied to several disorders including anxiety, depression, and schizophrenia