Reputable psychologists specializing in psychosomatics have voiced the figure of 80%. I think that doctors give a slightly smaller percentage.
And the reality, as usual, is different.
In my opinion, the connection between mind and body is so close that their mutual influence is always present.
It is unlikely that you will find such statistics anywhere, especially given the fact that many psychological and clinical schools believe that all diseases are psychosomatic, and each also sees them differently.
There are two main look at the problem.
From one psychological problem (you cannot express what is painful) - strictly one disease (sore throat);
There is no specificity, the same psychological problems can lead to different diseases, and an organ may not be associated with a disease at all, in which case each disease is individual.
On the other hand, many doctors consider all this to be the wildest delirium, and go try and prove to them that the throat hurts not because cold milk was drunk.
Both are quite logical , psychosomatics is a little less scientific, but all this has a right to exist. But the statistics are still unlikely to be found.