In addition to the bio-psycho-social development model, there is also the vulnerability-stress model (or diathesis-stress model), which is particularly useful as a visual explanatory aid. Vulnerability describes a person's vulnerability or susceptibility to developing a mental crisis or ultimately a mental disorder and varies from person to person.

These include, for example, unfavorable social living and developmental conditions, unfavorable (learned) characteristics such as excessive anxiety, female gender, the lack of an intimate, emotionally positive and supportive social relationship, and low self-esteem. However, these factors alone do not lead to the onset of depression. Only in interaction with certain demands/stressors can they contribute to it. Our vulnerability factors, which we all have, can have a significant impact on how we deal with the demands of our environment. Furthermore, the way in which a challenge or stress event is defined also plays a major role. This can be a traumatic life event (e.g. the death of a loved one) or everyday stress (e.g. at work).

If we now imagine a vessel, e.g. a barrel, the vulnerability factors ensure that it is already filled to a certain point. As the degree of vulnerability is very individual, each barrel is filled to a different level. Additional demands and stressors contribute to the level rising further. Of course, every barrel also has a tap where liquid can be drained. In our model, the tap can be equated with the protective factors described above and the coping mechanisms. Coping mechanisms describe the set of all action skills that enable a person to cope with demands and stress flexibly, efficiently and across different situations. However, if I have fewer protective factors, resources and coping mechanisms, i.e. I am less able to cope with the demands dripping or rushing into my barrel, it can happen that the barrel overflows and I experience a mental crisis, e.g. in the form of a depressive episode. The following illustration shows the "barrels" of three different people, all of whom have different levels of vulnerability and resources, which leads to the barrel filling up with further stress at different rates.