It depends on your workflow.
Ideally you would open a raw file with your raw edits into PS, make whatever PS edits you want, then use Save (not Save As) and LR should automatically import the new file. It will be a new/second file because PS writes as either a psd or tiff file, depending on your preferences. If you make no other edits to this in LR, and your client wants a change that requires PS, you can reopen it in PS via LR. Then you can Save again in PS and everything stays updated.
If, however, with your original psd/tiff file you made secondary adjustments in LR and then wanted to reopen, you'd end up with a bunch of files. Portrait.dng gets opened in PS and saved back to LR. You have a second file named Portrait.psd. Then you realize that it really needs to be slightly brightened and cropped. You brighten and crop the psd file in LR. Then you realize you made a glaring clone problem, so you want open Portrait.psd back into PS. Because you did the crop/brighten in LR and you want to edit that image, then you will end up with a third copy of this file, named something like Portrait-Edit.psd.
Does that make sense? If you only go between the original LR file and a single PSD file, your edits will always show up in LR. It is after you start making LR edits on a psd file that you will start to accumulate multiple versions of the same file.
Typically when you reopen psd files you will get a warning message with something like "do you want to open the original file or open one with LR adjustments?"
