Theory A vs Theory B

When to Use

Use when the client is stuck between two explanations for their experience: the threat-based interpretation (Theory A) and an alternative, often anxiety-based interpretation (Theory B). Originally developed for OCD and health anxiety but highly applicable in depression when comparing 'I am worthless/defective' (Theory A) with 'I have a belief that I am worthless, maintained by depression' (Theory B).

How to Introduce

Present both theories side by side: 'Let me offer you two possible explanations for what's happening. Theory A is the one your depression gives you. Theory B is an alternative. Let's write both out and look at the evidence for each, and see which one better fits all the facts.'

Adaptations

For depression, adapt Theory A to capture the depressive belief and Theory B to capture the CBT formulation account. For clients who struggle with abstract reasoning, use concrete examples and analogies. For those who intellectually prefer Theory B but emotionally feel Theory A is true, validate this discrepancy and use it as a focus for further work.

Avoid if the client cannot yet consider alternative perspectives or is so entrenched in their belief that presenting an alternative feels invalidating. Not appropriate as a first-session intervention; requires sufficient rapport and cognitive model understanding.

Clinical Tips

The power of this tool lies in the client generating evidence for both theories rather than being told which is correct. Theory B should not simply negate Theory A but offer a genuinely coherent alternative explanation. Use the two-theory framework as an ongoing reference point throughout treatment.