Diathesis-stress model (Psychology HL)

In one line: Some conditions appear only when a built-in vulnerability meets enough life stress — neither alone is usually enough.

The diathesis-stress model is a biological-approach explanation. A diathesis is a predisposition — often genetic — and stress is a triggering life event.

This links to the concept of causality: the model says the cause is an interaction, not a single factor. Two things together — nature and nurture — produce the outcome.

Memory hook: Loaded gun + trigger. A vulnerability plus a stressor produces the disorder.

Key idea: The diathesis sets the risk level; stress determines whether that risk turns into a disorder.

Take two students with different vulnerabilities to anxiety. Facing the same exam stress, the more vulnerable student develops an anxiety disorder while the other does not. Same trigger, different diathesis — so the outcome differs. The cause is the interaction.

Go further — higher-level insight: A high vulnerability needs less stress to trigger. Someone with strong genetic risk may develop a condition after only mild stress, while someone with low risk may cope with severe stress. This sliding scale is why the same event affects people so differently — a key evaluation point.

Key idea: The model is realistic and integrative, but the two parts are hard to measure precisely.

So the diathesis-stress model is a realistic, integrative explanation that avoids blaming a single cause, but a good evaluation notes vulnerability is hard to measure, the threshold for 'enough' stress is unclear, and it can underplay protective factors like support and resilience.

Watch out: Diathesis is a risk, not a destiny. Having a vulnerability does not mean a disorder is inevitable — without enough stress, it may never appear. Don't present it as fate.