The Evidence Pyramid

Not all studies are equal

The Evidence Pyramid, explained simply

From weakest to strongest: opinion and anecdote → lab/animal studies → observational studies → randomized trials → systematic reviews.

How it works, step by step

1. Anecdotes and expert opinion — useful for ideas.
2. Lab and animal studies — mechanisms.
3. Observational human studies — associations.
4. Randomized trials — test cause and effect.
5. Systematic reviews — combine all trials.

Evidence & sources

• Under GRADE, randomized trials start as high-certainty evidence and observational studies as low certainty, then are rated up or down. Evidence: established. Known: The GRADE framework. Unknown: A pyramid is a simplification — a poor trial can be weaker than a strong observational study. Source: GRADE Working Group (Guyatt et al., BMJ), GRADE: an emerging consensus on rating quality of evidence (2008).

Connected topics

• Correlation ≠ Causation
• Association vs. Evidence

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General education only, not medical advice. Drafted Oct 2026 · pending qualified expert review.