To write the discussion, you should have completed writing the results section and know the literature of your research topic in detail. If you didn’t finish reading literature, do that first. Otherwise, as a scientist you are probably never done reading, so let’s get started:
In the discussion, you are asked to place the results of your study into context with already published data about the research topic. Sounds easy, but most people find writing the Discussion sections hardest. I think writing this section asks for the most creativity and is therefore the most fun compared to all other sections.
At the end of the results section, you wrote a short summary of your results, so there is no need to repeat the results in the discussion, especially since the discussion always directly follows the results. Instead, you should screen the literature for publications that confirm, support or contradict your results. For example, did you analyze a parameter that was already analyzed by others by using another method? Cite the primary publication about this work and describe the most relevant parameters of this study. Do authors reach the same results and conclusion as you do? It’s great if they do, if not, why? What might be the distinguishing factor between the studies that caused the results to be different? It is ok if your results do not absolutely fit to already published data. Biological systems are variable and minor changes in the experimental setup can cause major differences in the results, you just need to provide the reader a possible explanation.
Contextualizing Results with Literature
You can also compare your results with studies that used a similar but not identical test system. For instance, if you used an animal model of Alzheimer’s disease, you can compare the results with results obtained from similar animal models, like animals that have a different mutation in the same gene or animals with a different promoter. When using an in vivo model, you can also check if your results fit to already published in vitro studies with the same hypothesis.
If your study is related to a disease, compare your results with studies performed with patients / human tissue of this disease.
In summary, you can pretty much discuss each parameter of your results with already published data. There are so many publications out there, that you will almost always find enough literature to discuss your research topic. While discussing, you should cite not only references that support but also references that contradict your hypothesis. This will allow the reader to get an overall picture of the topic.
When you describe already published data, use present tense, as all scientific data that are published after peer-review are supposed to be fact. BUT, when mentioning (not describing in detail!) your results in the discussion you should do it in past tense, as your data are not published and are therefore not fact yet.
Citations
The discussion is the first section in the manuscript-writing procedure where you definitively need to add citations. I would therefore like to shortly mention some key points: When reading into a new research topic, it is really helpful to read some review articles to get a good overview, but afterwards you have to take the next step and also screen the primary literature as you are required to cite primary literature in the discussion. Primary literature is an original article describing results of experiments that actually test a scientific hypothesis. You are thus definitively citing primary literature if you can find the statement you want to cite in the results section. Did you find the information in the introduction of an article, it is definitively not the primary literature and you have to check which article was cited there and look if this is the primary literature. Did you find the information you want to cite in the discussion, you have to check if authors I.: repeat their own results that are provided in the results section, II.: provide their own opinion or III.: cite another article. In the case of I. and II., you can cite this article as primary source. In case of III., you need to check the cited article and if this is the primary source, you need to cite that. Please make the effort and check, if the cited article really is the primary source, as many authors unfortunately cite quite imprecisely.
As a rule of thumb, you should avoid citing review articles in the discussion as much as possible. If you still need to do so, for example because you don’t want to discuss a topic in detail but still want to provide the reader the information where such a discussion can be found, you can cite a review article, but you should mention it accordingly: “…as reviewed by (Doe et al., 2020).”
At the end of the discussion, you need to provide a general conclusion of your study shortly repeating the overall results of your study, how they improve the existing knowledge of your research topic and how they might be utilized for future research. The conclusion should be really concise.
Today’s conclusion about the discussion section:
I:
Compare your results with already existing literature
