How to Write Study Limitations

The limitations paragraph tells readers where your study's design, data or analysis may have affected its results, and in which direction. It strengthens a paper by showing that you understand its weaknesses, and it helps readers judge how far to trust the findings.

What to cover

• Design: for example observational, so causality cannot be established.
• Sample: size, selection, single site, response rate.
• Measurement: misclassification, self-report, missing data.
• Confounding: variables not measured or adjusted for.
• Analysis: multiple testing, model choice.
• Generalisability: population and setting.

How to write each limitation

1. Name the limitation specifically.
2. Explain how it could have affected the results (direction and approximate size, if known).
3. Say what you did to reduce it, if anything.
4. State how it affects the conclusion.

Illustrative example

Invented for teaching. "Frailty was not recorded in the hospital database, so we could not adjust for it. Because frail patients tend to have surgery later and more delirium, this may have exaggerated the apparent benefit of early surgery. We examined the effect of age and comorbidity as proxies, which did not change the result. The findings should be confirmed in studies that measure frailty."

What not to do

Avoid generic statements ("the sample size was small") with no consequence, avoid listing too many minor items and avoid hiding major limitations at the end of a long paragraph. Many journals encourage a dedicated limitations paragraph.

Where to place limitations

Most journals expect a limitations paragraph near the end of the Discussion, before the conclusion. Put the most important limitation first, because readers may stop after a sentence or two. If a limitation could change the conclusion, say so directly and soften the conclusion to match, rather than relegating it to a final line. Check the target journal's template, since some require a headed "Strengths and limitations" subsection.

Common pitfalls

• A list without explanation of impact.
• Claims that limitations "do not affect" results without evidence.

Key takeaways

• Be specific, explain the likely effect and state how conclusions are affected.
• Honesty increases credibility.

This page is general educational information about research methods. It is not medical, legal or regulatory advice; follow your institution's ethics board and your target journal's instructions.