What are study limitations?
They are simply the things you didn’t study. This is normal, because you can’t study everything.
The point of the limitations section is not to write everything that’s wrong with your study. It’s simply to address what wasn’t possible yet within the constraints (i.e. scope) of your current study, and to explain how these limitations could be addressed in follow-up research.
Clearly define your study's scope upfront
By clearly describing the scope of your study in the Introduction (i.e. what you will and will not study, and why), your reviewers will know what they can expect from your paper.
Some limitations are related to specific research questions, others apply to the entire study. In any case, it’s helpful and interesting to discuss how these limitations can be addressed in future research.
Types of study limitations
Most limitations fall into one of these categories:
- Scope limitations: variables, sites, populations, or conditions you didn’t include (e.g. testing one temperature range, one species, one region).
- Method limitations: constraints of the tools or design you used (e.g. a survey that can’t capture causation, a sample size too small to detect small effects).
- Generalisability limitations: reasons your findings may not extend beyond your specific context (e.g. lab conditions vs. the real world, one population vs. a broader one).
- Data limitations: gaps or noise in the data itself (e.g. missing data, self-reported measures, short follow-up time). This doesn’t mean the data are bad! Perfect data don’t exist anyway. It just means there are limits to what you can do with them.
How to discuss study limitations
A clear limitation paragraph usually does three things:
- Name the limitation: state plainly what wasn’t studied.
- Explain why it matters: using evidence or reasoning, explain why this limitation matters (or doesn’t, in some cases).
- Point to future solutions: briefly note how a follow-up study could address the limitations.
Example of how to discuss a study limitation
Limitation: The current study works with a set range of environmental variables that result in growth rates specific to those environmental settings. Why this is a limitation: However, it is well known that seedling growth rates are determined by a myriad of environmental drivers (Krauss et al. 2008), and the growth we observed in our experiment may differ widely in drier, more salty, darker, or otherwise different environments (e.g., Kodikara et al. 2017b; Sloey et al. 2022). This could result in shorter shoots or roots than we measured in our experiment and reduce erosion or accretion thresholds. Future work: Therefore, the effect of these and other environmental differences is worthy of further study in the context seedling establishment in sedimentary dynamic environments.
Look up study limitations in your own field
The above example is just one, for a specific type of study. Check the journal or subdiscipline you’re writing for to find examples of how to discuss the limitations in your field.