What is... psychology series

What Is… a Diathesis-Stress Model?

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.  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.  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 given that the prominent symptoms in my illness are ones that tend 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.


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10 thoughts on “What Is… a Diathesis-Stress Model?”

  1. This makes a lot of sense. I’d been thinking along those lines about myself. I think my autism makes me vulnerable, and some difficult childhood events are in there too as long-term stressors, but the actual triggering events for my depression were fairly trivial and my depression seemed really out of proportion; later episodes of depression didn’t even have any obvious triggers.

  2. It’s very interesting to think in my own case. 4 out of 5 immediate family members have developed a mental illness. I wonder why that is? And why only 1 did not develop an illness.

  3. My own illness is complex. I found this post interesting though, because it pin-points a possible CAUSE. I have had various ‘stressors’ (trauma) since I was four years old. I was in care as a child with a couple who had their own massive problems who damaged my self-esteem and psyche further. There is a history of mental illnesses in my biologic family, some diagnosed, others not. Depression is intertwined with all of them to a degree. My own ‘breaking’ point I believe was when puberty hit. Perhaps the traumas suffered previously were enough to make me vulnerable to the hormonal changes that puberty brings. Perhaps it was biology. Or it was my broken self esteem coupled with the angst that teenagers often have, that provoked a home environment that further triggered the mental illness.

    I have two siblings, neither of which developed the same (or any at all) mental illness issues that I did. But some of their children have a milder form of the familial depression and all of one sibling’s children have had therapy.

    You have given me some things to consider when discussing my problems NOW (forty five years after the onset). Thanks Ashleyleia!

  4. So fascinating. My paranoia/schizophrenia didn’t develop until 2005, when I was 27 or 28 years old. There was definitely the stress of my evil coworkers involved, and they did a lot of things that would make anyone paranoid. Looking back, though, I probably had a propinquity for paranoia from a young age, but I was never stressed enough for it to fully show, I guess? Then with mood swings/bipolar, that hit hard with adolescence. I think that was more hormonal than stress-induced, but a lot of it had to do with suddenly feeling emotionally needy (due to the presence of hormones), which went back to my childhood, I’d wager. Then with my winter obsessive/depressive issues (it’s varied over the years), that sprung from (my best guess) gradual exposure to my mother and her negative thought patterns, combined with some sort of climate/winter issue.

    I definitely think this theory of yours holds weight. Whenever you hear about a psychotic break from reality, that’s what it was–stress. I’d love to find out if anyone ever became schizophrenic during happy times (not counting mania as a factor); my point being that I wonder if schizophrenia could ever manifest if your life is going along splendidly. Huh.

    Great blog post!! Much food for thought.

    1. I’ve seen people whose first psychotic break came when otherwise things were okay. Schizophrenia is probably the illness where there’s the strongest genetic contribution, so in people who are highly genetically loaded it doesn’t take much.

  5. It fits very well with my illness. Strong genetic tendency toward depression (my mother and 2 of her 3 sisters, me, my sister and my daughter) plus some earlier life stresses which contributed to vulnerability and less flexible coping strategies, but it wasn’t until the major life stress of having a baby which is when the cracks really started to show.

    There’s a lot of research from the Dunedin Study (a lifelong cohort study of 1000 people born in Dunedin in one particular year which is a prolific generator of academic papers) which supports this model. There was a great documentary made about this study and its implications for public provision and funding of support for families with small children and early intervention programs (unfortunately it was geo-blocked outside of NZ and Australia and they haven’t made a DVD available for sale 😕 otherwise I’d provide a link).

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