How to Write an Effective Discussion

Abstract

Explaining the meaning of the results to the reader is the purpose of the discussion section of a research paper. There are elements of the discussion section that should be included and pitfalls that should be avoided. Always write the discussion section for the reader. Remember that the focus is to help the reader understand the study and that the focus should be on the study data.

Introduction

You have carefully written your hypothesis. You have designed the study and collected the data. You have conducted the statistical analysis and grouped the summary results into tables and graphs. But what does it mean? Explaining the meaning of the results is the purpose of the discussion section. Although the discussion section comes at the end of the paper, you should be thinking about what you will write in this section from the moment that the study is conceived. Topics that you will develop in the discussion section should be considered from the study’s outset: Why is the study important? How does this study relate to previous studies? What are the limitations of the study design? There are elements of the discussion section that should be included and pitfalls that should be avoided (Tables 1 and 2). Most important, always write the discussion section for the reader. The discussion section is not a forum for you to impress others with your knowledge of the subject. You should be trying to convince the reader of the merits of the study. This paper is an update of a paper I wrote on this topic previously but with contemporary examples and some new ideas.¹

Table 1.

Elements to Include in the Discussion Section

Table 2.

Things to Avoid in the Discussion Section

Elements to Include in the Discussion Section

State the Major Findings of the Study

The discussion section should begin with a statement of the major findings of the study. This should be in the very first paragraph of the discussion section. It should be a direct, declarative, and succinct proclamation of the study results. Some authors begin the discussion section with a few sentences as an overview of the study, but this is not necessary. The discussion section should not begin with data or elements of the study design. For example, Kaur et al² begin the discussion section of their paper with the sentence, “Our findings suggest that ETT [endotracheal tube] scraping with an ETT suction catheter with balloon-sweeping technology, compared to standard ETT suctioning, did not significantly improve subject outcomes. Results were similar between the intent-to-treat and the per-protocol analysis after excluding subjects who did not receive planned extubation.” As another example, Beuvon et al³ begin their discussion section with, “In this physiological crossover study, subjects with COPD exacerbation significantly improved their FEV₁, FVC, and PEF [peak expiratory flow] after salbutamol vibrating-mesh nebulization through HFNC [high-flow nasal cannula] as compared to HFNC alone, suggesting an effective bronchodilator effect.” Both examples present the reader with the main findings that are then explained in the ensuing paragraphs.

Explain the Meaning of the Findings and Why the Findings are Important

No one has thought as much about your study as you have. As the person who conceived, designed, and conducted the study, the meaning of the results and their importance seem obvious. However, this might not be so clear for the person reading your paper for the first time. One of the purposes of the discussion section is to explain the meaning of the findings and why they are important, without appearing arrogant, condescending, or patronizing. After reading the discussion section, you want the reader to think, “That makes perfect sense. Why hadn’t I thought of that?” You do not want to force the reader to go through the paper multiple times to understand what it means. Most readers will not go to that effort and your findings will be overlooked, disregarded, and forgotten.

Relate the Findings to Those of Similar Studies

No study is so novel and with such a restricted focus that it has no relation to other previously published papers. The discussion section should relate your study findings to those of other studies. Questions raised by previous studies may have served as the motivation for your study. The findings of other studies may support your findings, which strengthens the importance of your study results. Arias-Sanchez et al⁴ write, “Previous studies in stable subjects without oxygen support have shown that, compared with standard oxygen therapy, the use of HFNC is associated with a smaller decrease in ${\text{S}}_{{\text{pO}}_{\text{2}}}$ during fiberoptic bronchoscopy.” Or, your findings might differ from those previously reported. For example, Støve et al⁵ write, “In contrast to our expectations, the main findings showed low-to-moderate agreement between the Apple Watch Series 7 and the Garmin Vivosmart 4 compared with the comparator measure during rest or after physical exercise. This finding contradicts previous studies, which suggested that the Apple Watch Series 6 has a high agreement with pulse oximeters at rest in healthy populations and patients with lung disease.” A reflection on how your study results agree or conflict with the existing literature is important in demonstrating that you have carefully reviewed the literature and can place your findings in the appropriate context.

Consider Alternative Explanations of the Findings

Despite efforts to remain objective and to maintain equipoise, it is easy to consider only those explanations that fit your bias. It is important to remember that the purpose of research is to discover and not to prove. It is easy to fall into the trap of designing the study to prove your bias. When writing the discussion section, it is important to carefully consider all possible explanations for the study results rather than just those that fit your biases. As an example, Miller et al⁶ write, “RTs [respiratory therapists] intubating during cardiac arrests may also be more experienced and preferred to use direct laryngoscopy, although we were unable to capture the experience level of the RT making each attempt or the rationale for why each method was chosen.” RTs were less likely to use videolaryngoscopy during cardiac arrest. This can be explained by the experience level of the RT. But limited portability of the equipment is another plausible alternative explanation.

State the Clinical Relevance of the Findings

The reason we conduct studies is usually to improve the care of our patients. Thus, it is important to cast the findings of your study in the context of clinical practice. For which patients do the results apply and for which do they not apply? Experimental studies conducted in the laboratory usually do not involve human subjects, but the results may have clinical implications, which should be stated. A paper by Sameed et al⁷ commented on the clinical relevance of their laboratory study. “From a clinical standpoint, a difference of 10–20% in WOB [work of breathing] might not seem like a drastic difference and perhaps deemed insignificant in the assessment of extubation readiness. However, we showed that how a ventilator behaves on zero PSV [pressure support ventilation] and zero PEEP depends on the proprietary software and that the specific ventilator design might end up imposing higher or lower WOB compared with baseline and the T-piece.”

It is important to distinguish between a measurable difference and a meaningful difference. Particularly for bench studies, there is little variability in the data and thus the standard deviation is small. This might result in differences that are statistically significant but not clinically important. It is important to address this in the discussion section because not all statistical differences should result in changes in practice. For example, a bench study might report a small but statistically significant difference in patient work of breathing for a new ventilator brand or ventilator mode but that difference might be so small as to be unlikely to promote superiority of the ventilator or mode.

Acknowledge the Study’s Limitations

All studies have limitations. Unfortunately, the limitations of some studies are fatal flaws that preclude publication; these studies are typically not accepted for publication. However, even the best studies in the most prestigious journals have limitations. It is far better to identify and acknowledge your study’s limitations than to have them pointed out by a reviewer or by a reader in a letter to the editor after publication. See the example in the study by Kaur et al,² “This study has several limitations. First, this was a single-center study with institutional-specific ventilation weaning protocols. Second, the treatment allocation could not be blinded to the clinicians, which might have led to a bias due to clinicians being aware of the experimental device. Third, . . .” They identify 4 limitations. Some authors attempt to balance the limitations by listing strengths as well as limitations. Generally, it is better to allow the reader to identify strengths of the study. An overt statement by the authors of their perceived strengths of their study might be viewed as self-congratulatory or an attempt to minimize the limitations.

Make Suggestions for Further Research

Although a study may answer important questions, other questions related to the subject may remain unanswered. Moreover, some unanswered questions may become more focused because of your study. You should make suggestions for further study in the discussion section. Laboratory experimental studies typically lead to suggestions for follow-up clinical studies with human subjects.

Give the Take-Home Message in the Form of a Conclusion

What is the take-home message? What do you want the reader to remember from your study? The take-home message should be the first sentence of your conclusions section. In some journals, the conclusions are given in a paragraph or subsection at the end of the discussion section, whereas other journals (Respiratory Care, for instance) require a separate conclusions section. The conclusions section might also provide suggestions for practice change, if appropriate. The conclusions section should be a concise short paragraph. An example of a well-written conclusion comes from a study by Kondo et al,⁸ who wrote, “Although Ellipta and Diskus have similar internal resistances, the threshold flow of particle dispersion of Ellipta was almost half that of Diskus. This arises from the different distribution of main and side flows in the devices, and once particle release is initiated, the release may continue until its completion. Ellipta may be a preferred device for patients with reduced pulmonary function.” Note that an original research paper has a conclusions section, not a summary section. A summary section is written for a narrative review and summarizes the important points in the review.

Things to Avoid When Writing the Discussion Section

Brevity and Verbosity

There is no firm rule with regard to the length of the discussion section. Avoid 1 and 2 sentence paragraphs; these should be expanded or collapsed into the preceding or following paragraph. Each paragraph should focus on one idea or concept. Lengthy paragraphs are difficult to read. Start a new paragraph when you shift to a new idea. Remember what we were taught in our undergraduate English classes: a paragraph should consist of a topic sentence, supporting sentences, and a concluding sentence. A paragraph will typically be ∼100 to 200 words.

Overinterpretation of the Results

It is easy to inflate the importance of the results. Be careful that your interpretation of the results does not go beyond what is supported by the data. The data are the data: nothing more, nothing less.

Unwarranted Speculation

There is little room for speculation in the discussion section. The discussion section should remain focused on your data and the subjects and/or devices in your study. If the subjects in your study had asthma, it is usually not appropriate to speculate about how your findings might apply to other patient populations such as those with COPD. If your study used volume control ventilation, it may not be appropriate to speculate about how the findings might apply to pressure control ventilation. If you feel compelled to speculate, be certain that you clearly identify your comments as speculation: “We speculate that . . .”

Inflating the Importance of the Findings

After all the hard work that goes into a study, it is easy to attribute unwarranted importance to the study findings. We all want our study to make an important contribution that will be cited for generations to come. However, unwarranted inflation of the importance of the study results will repulse editors, reviewers, and readers. A measure of humility goes a long way. Avoid the use of words such as “novel” and “the first study” and “impressive” when referring to your work.

Tangential Issues

It is important to remain focused on the hypothesis and study results. Injecting tangential issues into the discussion section distracts and confuses the reader. Tangential issues run the risk of diluting and confusing the real message of the study.

The Bully Pulpit

Do not use the discussion section to criticize other studies. Although you should contrast your findings to other published studies, this should be done professionally. Do not use the discussion section to insult other investigators. Moreover, never preach to the reader.

Conclusions That Are Not Supported by the Data

The hypothesis, methods, data, and conclusions should be a tight package. The methods are related to the hypothesis, the data are generated by the methods, and the conclusions are supported by the data. Avoid the temptation to allow your biases to enter the conclusions. Conclusions that are not supported by the data result in the reader questioning the objectivity of the author.

Summary

The discussion section is your opportunity to explain the meaning of your results. The discussion section pulls together the message of the paper. When writing the discussion section, remember that the focus should be to help the reader understand the study and that the highlight should be on the study data.