Hi,

I completed my 1st study two years ago which I wrote up as a complete chapter, including discussion and conclusion. Based on the results and findings of that completed study, my next study was designed.

Do I now (two years later) need to go back to that discussion in that initial study and update the reference to literature in the discussion with more up to date articles, or is it OK to make reference to the new literature in the overall discussion chapter in the thesis and the literature review of the thesis? I suppose I am asking is that my 1st study was time stamped in a way. Is that OK to keep it that way?

I would say, yes, you need to update it. If something has changed since the updated literature that would have affected the way you conducted the study then you should mention that, and say that the literature wasn't available until xxx date.