Discussing the Limitations of Your Research

Why discuss limitations

Even the most well-planned studies have limitations. This is not just because all research has constraints in terms of time, place, equipment, funding, and data access, but also because study design inevitably includes decisions and trade-offs.

Most journals will now expect you to discuss the limitations of your research in your paper. By discussing the limitations of your study in a thoughtful way, you can highlight your specific contribution.

You can also use the limitations section to anticipate and address potential editor and reviewer concerns by demonstrating an in-depth understanding of your field and attention to methodology.

Finally, an effective limitations section allows you to increase the impact of your work by underscoring the need for future research by your team and other scientists in your field.

Common research limitations

Although the details of the limitations vary with a specific paper, there are some common trends to research limitations that affect many studies.

Sample size and profile

If your study has a small sample size, this may have impacted your ability to perform certain statistical analyses or extend its findings to the general population.

Larger studies can also be affected by sample bias, whether with respect to age, gender, and nationality.

In certain cases, a limited sample size or profile may be intentional: for example, perhaps your study focused on a small regional hospital to investigate the effects of a treatment in an understudied ethnic group. Nonetheless, it is important to be forthright about how this focus affects the generalizability of your research.

Lack of data or previous research

If you were reporting on a new and rare mineral or an uncommon disease profile, your work may have been affected by a lack of available data.

If you conducted a study in an emerging area in which limited existing literature was available, your study may have been more exploratory than anticipated, or otherwise impacted because you could not consult with previous studies.

Methodology and equipment

Every research approach has intrinsic benefits and limitations. A treatment is promising in a rat model, but further research is needed before it is brought to clinical trials. A new material has promising properties in the laboratory, but much more work is needed to explore industrial applications.

In your study design, you made careful decisions about how to collect data, whether by conducting phone surveys or searching databases. Although your method was the most effective for your purposes, as all methods, it had known or unexpected drawbacks that you may want to state.

Your study may also have been constrained by the available equipment. Perhaps the best measurement tool you had access to still has limitations in terms of precision.

Time, access, and funding constraints

Time constraints can make it difficult to accurately assess long-term effects, such as the side effects of a new treatment, or long-term wear on new equipment.

Your study could also have been affected by the time period in which it was conducted, such as if you were studying farming practices during a year that was particularly rainy.

Access constraints could have impacted your research if you were studying a group or a place that is difficult to access for legal, sociopolitical, or funding reasons.

Sometimes, equipment and methodology are limited by the expense of acquiring specific materials, or by national and institutional research guidelines.

As a researcher, you had to make choices during the course of your research because of time and funding constraints. Multiple explanations for a particular molecular mechanism emerged, but you had to choose one for further investigation.

Where to discuss limitations.

Limitations should generally be addressed in the Discussion and before the Conclusion.

Some journals will ask you include a specific section for the limitations or to address limitations and strengths together. Others have a more free-flowing approach to the structure of the Discussion, or would like to see limitations incorporated throughout the paper. As always, it is best to confirm with your target journal’s guidelines and review recent papers from the target journal to ensure your paper is appropriately structured.

How to discuss limitations

Introduce the limitations section

Start with a declarative introductory statement such as “It is necessary to acknowledge the limitations of this work,” or “This study had three important potential limitations.” Focus on the limitations that had the most impact.

Specify the limitations

Each limitation should be discussed in sufficient detail to convey how it may have affected your results. You might start discussing a given limitation with, “Because this study aimed to investigate a rare disease in a specific population, we had access to a limited sample size, which may have affected the generalizability of this work…” or “The equipment we used to experimentally validate the proposed method had limitations, which impacted the accuracy of our results…” Unless the limitation is outstanding and requires extended discussion, this can be a precise summation within three sentences of 1) the limitation, 2) the reason for it, and 3) its impact on the study.

Propose a direction for future studies

A strong way to finish is to propose how future studies should build on and address these limitations. You might write, “A future study with a larger cohort size is needed to…” or “In our future work, we intend to investigate…” In this way, an effective limitations section will leverage the limitations of the present work to create opportunities for further exploration.