In this series, I dig a little deeper into the meaning of psychological terms. This week’s term is diathesis-stress model.
Okay this week’s term may sound a bit obscure, but bear with me, because it’s actually quite relevant. A diathesis-stress model, also known as stress-vulnerability model, 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. The concept was first described by psychologist Marvin Zuckerman in his 1999 book Vulnerability to Psychopathology.
Diathesis meets stress
This model recognizes the interplay between underlying vulnerability (i.e. diathesis) that predisposes someone to illness and environmental stressors. There’s a certain threshold or critical level at which a psychological disorder will develop. Reaching that threshold requires both both a stressor and a diathesis, with the proportions depending on the individual. Someone with greater vulnerability would require a much less significant stressor to reach that threshold than someone with minimal vulnerability. This provides an explanation for why two people might be exposed to the same situational stressors but respond quite differently. It also means there’s no single root cause; there’s a combination of factors.
Because vulnerability is latent until a disorder develops, it’s difficult to measure. Vulnerability can involve both biological and psychological factors, including genetics, biology, physiology, cognitive styles, 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. The accumulation of stressors in combination with vulnerability doesn’t just have an additive effective, it has a multiplicative effect, so people can become essentially powder kegs ready to blow.
Applying the model
Diathesis-stress models have been used to describe a number of mental disorders, including depression and schizophrenia. It’s also part of dialectical behaviour therapy (DBT) developer Marsha Linehan’s biosocial model of borderline personality disorder.
I think this is a really interesting way of looking at the development of mental illness. My first episode of depression came after a significant interpersonal conflict with my ex-boyfriend. He 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 since the prominent symptoms in my illness tend to be more biological.
How do you think this model fits with your own illness?
- Colodro-Conde, L., Couvy-Duchesne, B., Zhu, G., et al. (2018). A direct test of the diathesis–stress model for depression. Molecular Psychiatry, 23(7), 1590-1596.
- OpenTextBC: Psychology: Perspectives on Psychological Disorders
- Wikipedia: Diathesis-stress model