Responding to Letter to Editor: Pros vs. Cons?

[Ruralguy]

I think you would want to discuss in as much detail as you can in the letter *why* you think various biases aren't likely to be relevant here because that probably will be the direction most experience scientists (social or physical) would think of. What you have written here is a good start.

[Caracal]

My approach would be to structure the response along the lines of:
(a) you agree with the letter writers that the finding is unexpected and contrary to current theories
(b) however, it has recently been replicated in X, Y and Z studies, making it less likely that it is a spurious finding
(c) the mechanism remains unknown, but A, B, and C are possibilities
(d) propose some approaches future research could take to test those possibilities

I know your example is hypothetical, but supposing it is something similar to your example, one obvious possibility is that you have survivorship/selection bias. That is, people who experienced adversity and were still alive and healthy and functional enough to participate in the study at whatever time childhood history was assessed are insensitive or resilient to stress in ways that increases longevity (I think this is sort of what you're suggesting)? Whereas the population of people who are more negatively affected by adversity are missing from the study. e.g.,  You see this pattern with a lot of outcomes if you select for people who have experienced a trauma but *haven't* developed PTSD-- they look better than the general population on all sorts of measures because you've essentially selected for resilience.

Wow, I think I'm going to use your template, thank you and I wish I could add you on my acknowledgements!!

Selection bias is very unlikely based on the large sample I have and who is in the data.

Survivorship bias is possible, but if that were true, in my hypothetical example, why would adults who experience childhood poverty die sooner vs. adults who experience child abuse die later (in my real paper, [poverty] and [abuse] are much more similar, measured at the same point in life, with the same severity, etc.). Both are in the same construct of "childhood trauma" but they have opposing results. If my child abuse results are based on flawed methods, then the rest of my findings should be flawed too, but there's no debate on them because "they make sense".

That seems like something you could say in your response as well. It could be that there is a survivorship or reporting bias, but if there is, that calls for a much larger rethink about the data that is being used in the field. That also helps with not sounding too defensive. The tone I would think you are going for is "I agree, there's something weird here, but the study design was sound, so we need to figure out what's going on here."