In this series, I dig a little deeper into the meaning of psychological terms. This week’s term: diathesis-stress model
Okay this week’s term may sound a bit obscure, but bear with me, because it’s actually quite relevant. It’s a model that is used to explain the course of a mental disorder based on the interaction between biological vulnerability and the stress caused by the environment and life experience. It’s not an either-or proposition, but rather a recognition that it is the interplay between these elements that can lead to illness. The term stress-vulnerability model is also used.
A diathesis-stress model suggests that there is a certain threshold or critical level to develop a disorder. If the biological and experiential factors interact in a certain way, the individual will go on to develop the disorder. A person with the same biological vulnerability (i.e. an identical twin) who was not exposed to that level of stress in the environment may never go on to develop an illness. Similarly, two people experiencing the same environmental stressors may have very different responses depending on their inherent vulnerability.
Because vulnerability is latent until a disorder develops, it’s difficult to measure. Vulnerability includes factors related to genetics, biology, physiology, cognition, and personality. Some disorders may have a window of vulnerability, a period of life during which environmental stressors are most likely to activate latent biological vulnerability.
Environmental stressors can be acute or chronic. A single stressful event may not be enough to trigger illness. but the accumulation of multiple stressful life events may trigger activation of the latent vulnerability. While stress can trigger the emergence of the disorder, the disorder in and of itself also causes stress.
An example of a diathesis-stress model is the biosocial model of borderline personality disorder put forward by Marsha Linehan, who developed dialectical behaviour therapy (DBT). Diathesis-stress models have also been proposed for depression, anxiety disorders, schizophrenia, bipolar disorder, and alcoholism.
A study in the journal Molecular Psychiatry on people with depression concluded that “our findings point to an extra risk for individuals with combined vulnerability and high number of reported personal life events beyond what would be expected from the additive contributions of these factors to the liability for depression, supporting the multiplicative diathesis-stress model for this disease.”
I think this is a really interesting way of looking at the development of mental illness. For me, my first episode of depression came after a significant interpersonal conflict with my ex-boyfriend, who had remained my best friend after I broke up with him, right up until he started dating someone and decided we shouldn’t be friends anymore. It was a significant life event, for sure, but it’s far from the biggest life stressor I’ve had, and it certainly didn’t seem bad enough in proportion to how sick I was.
That happened in my late 20s, and there was no clear indication of depression before that. From a diathesis-stress perspective, that would be latent vulnerability. That stressor at that time was enough to activate that latent vulnerability. That makes a lot of sense, especially given that the pattern of symptoms I’ve experienced with my illness tends to be quite biologically based.
How do you think this model fits with your own illness?
You can find the rest of my What Is series here.
My book Making Sense of Psychiatric Diagnosis breaks down the different categories of DSM-5 diagnoses, explaining the diagnostic criteria and providing first-hand stories of the various illnesses. It’s available on the MH@H Store, as well as Amazon and other major retailers.