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The diathesis-stress model explains how genetics and environmental stimuli interact to cause mental illness. Genetic vulnerability can increase the likelihood of developing a disorder when exposed to stressors, while those with less vulnerability can handle more stress without developing a disorder. Environmental stressors vary greatly, making it difficult to isolate a specific cause of mental illness. Biological, developmental, and social influences can also play a role.
In the case of a psychological disorder such as depression, the cause is never just genetic or environmental, but a complex interaction between the two. The diathesis-stress model is one way to understand the interaction of genetics and environment in causing mental illness. According to this model, people inherit a genetic tendency towards a mental disorder – diathesis – which is influenced by environmental stimuli – stress – to cause the disorder to appear.
The diathesis-stress model shows the inheritance of vulnerability to a specific condition such as depression, anxiety or addiction. For a more vulnerable person, less environmental stress is required to trigger a mental illness. A person with very little vulnerability can handle high amounts of stress without developing a mental disorder.
For example, many soldiers go to war and experience traumatic events, however, not everyone develops a mental illness such as post-traumatic stress disorder (PTSD). This is because some soldiers have a genetic predisposition to PTSD, while others do not. Those with a genetic vulnerability are much more likely to have PTSD triggered by a traumatic event. Soldiers with less genetic vulnerability can experience the same event without developing the same disorder.
The diathesis-stress model shows how genetic inheritance can have a major influence on behavior. Researchers estimate that about half of a person’s personality traits and cognitive abilities are due to genetics. The remainder may be due to a variety of developmental and environmental factors.
In the case of mental illness, it is often much more complicated than isolating a single gene responsible for the disorder. For most mental disorders, many genes have a small effect, and the cumulative influence of all these genes together is what leads to mental illness. This can make researching the genetic background underlying a psychological disorder very difficult.
The diathesis-stress model shows that genes are only part of the picture in the case of a psychological disorder. Environmental effects are equally important in causing mental illness. These environmental stressors can vary greatly from person to person, making it difficult to isolate a specific cause or factor leading to mental illness.
Biological influences such as excitation of the nervous system in a stressful situation may be a type of environmental stress referred to in the diathesis-stress model. Developmental and social influences, such as how a person was brought up and how those around them respond to a stressor, can also play a role.
