Preview
The Diathesis-Stress Model
IB DP Psychology — Biological Approach | SL & HL | Paper 1
🎯 Learning Intentions By the end of this note, you will be able to:
- Define the diathesis-stress model, diathesis, and stress using IB-aligned terminology.
- Explain how a biological vulnerability interacts with environmental stressors to produce psychological outcomes.
- Describe the role of genetic predisposition and lived experience in shaping behaviour and mental states.
- Evaluate research evidence for the diathesis-stress model using supporting and opposing studies in ACAS format.
- Apply the diathesis-stress model to a real-world case study from the biological perspective.
- Discuss the extent to which the diathesis-stress model provides a complete explanation of psychological vulnerability.
- Analyse the model using relevant concept areas: Causality, Perspective, Bias, and Responsibility.
Introduction & Context
Consider two students who both experience the same stressful event — a serious family breakdown during their final year of school. One student feels shaken but recovers within a few weeks, returning to normal functioning. The other develops persistent anxiety, withdraws from friends, and struggles to concentrate for months. Both faced the same external pressure. So why did they respond so differently? This question sits at the heart of one of psychology's most important frameworks for understanding vulnerability.
For much of the twentieth century, psychologists debated whether psychological disorders were caused by biology — genes, brain chemistry, neurological structure — or by life experience and environment. This nature-versus-nurture framing, while intellectually useful, ultimately proved too simplistic. Real human behaviour rarely has a single cause. What emerged from decades of research was a more nuanced model: one that treats biology and environment not as competing explanations, but as interacting forces. The diathesis-stress model is that framework.
The model proposes that psychological difficulties arise from the combination of a pre-existing biological vulnerability and a triggering environmental stressor. Neither alone is sufficient — it is the interaction between the two that produces the outcome. This makes the model both scientifically powerful and deeply humanistic: it acknowledges that people are not simply victims of their genes, nor are they simply products of their circumstances.
🔑 Analogy — The Cracked Vase Imagine a ceramic vase with a hairline crack running through its base — invisible to the naked eye, but structurally present. If you place the vase gently on a shelf, it holds perfectly. But if you fill it with heavy stones, the crack gives way and the vase shatters. The crack is the diathesis — the hidden vulnerability. The stones are the stressor — the environmental pressure. Neither alone destroys the vase: a crack without weight causes no problem, and a vase without a crack can hold the stones. It is only when both are present that the outcome occurs.
Core Concepts
To understand the diathesis-stress model fully, it helps to first examine its two components separately before exploring how they interact. The first component — diathesis — refers to the biological side of the equation. Think of it as the internal architecture a person inherits or develops early in