Bidirectional relationships

In one line: In a bidirectional relationship, two things each cause the other — round and round.

Think of stress and sleep. Stress makes it harder to sleep. But poor sleep then makes you more stressed the next day. Each one feeds the other in a feedback loop — that is a bidirectional relationship.

Memory hook: Not a line, a loop. Bidirectional = the arrow points both ways.

The concept behind it: Bidirectional relationships are a causality idea: they show that a simple, one-way 'A causes B' is often too simple. Real behaviour is full of loops.

This matters for how we read research. If a study finds low mood and social withdrawal go together, it is tempting to pick a direction. But they may be bidirectional — low mood leads to withdrawing, and withdrawing deepens low mood — so neither is simply 'the cause'.

Go further — higher-level insight: Feedback loops make problems self-sustaining — and point to where to break them. In therapy, you don't have to find 'the original cause'; breaking any part of the loop (improving sleep, or gently increasing activity) can slow the whole cycle.

How this is tested: In a Paper 2 Section B answer on causality, spotting a bidirectional relationship is a high-level move: instead of just saying 'we can't tell the direction', you explain that the direction may run both ways in a feedback loop.