If you have weaker morning erections post finasteride use; then it is a reasonable indicator that the problem is physical as opposed to psychological.
This is because this erection is not controlled by thoughts conscious or subconscious thought by and large- but the body’s natural response to the circadian hormonal rhythm and appropriate hormonal levels and adequate function of the penis.
If the body is not responding as it did prior to finasteride, then it is likely that there is some defect, be that hormonal or structural (in terms of the penis).
Weaker in the above context means “poorer erections”, I hope that clarifies.
It might sound very awkward to know whether erections or weaker/poorer post finasteride use if the differences are small and you are unsure about the matter.
Of course it can be very difficult to know unless the change in erectile function in morning erections is very noticeable and the change significant. Whilst it probably isn’t possible to know what erectile function was like prior to the use of the drug, unless you had prior studies in this area, it is possible to have erectile function evaluated with a competent urologist who can consider your current circumstances. This is done via overnight stamp/rigidity testing and other such means.
The point is that if you know or strongly believe that erectile function is poorer post finasteride use;
You can consider morning erection as a helpful indicator of potential problems and if you have much poorer morning erections or no morning erections and this is a problem that you did not suffer from prior to finasteride; you can consider that this mean the probably is likely to exist because of a real problem and not a psychological one. You can then seek out an endocrinologist and urologist to assess hormones and erectile function respectively.
I hope this explains what you can do with the information that your body can provide for you.