The term “diathesis” is used to describe an individual’s vulnerability or a predisposition to a particular medical condition. These predispositions can be physical as well as psychological. Initially, psychiatrists used this term in relation to the study of schizophrenia and then to depression. In fact, it’s often used to discuss individuals with suicidal tendencies.
Often, a diathesis is a biological or genetic factor—a vulnerability we’ve inherited in our genes; but it can also be an environmental factor such as a traumatic event in early childhood; and, it could be a vulnerability that developed from an interaction between a person’s genes and environmental factors.
This model is helpful for mental health practitioners as well as patients because it describes how the interaction between a vulnerability and environmental stress may lead to the development of a mental health disorder. In fact, sometimes this model is referred to as the “stress-vulnerability model.”
A predisposition for a certain condition is, of course, a vulnerability. When that vulnerability is subjected to stress, the person is more likely to develop a disorder as a result. A person who does not have a predisposition may also develop a disorder, but typically as the result of significantly more stress than what might trigger a person who has a genetic predisposition.
The diathesis-stress model supposes that mental health disorders are caused by a predisposition and stress. Researchers suggest that this combination of predisposition and stress is why some individuals develop mental disorders and others do not.