PhD students are 2.5 times more likely to develop psychiatric disorders than highly educated general population.
Calling yourself “doctor” if you don’t hold a PhD earned in Germany is a criminal offense.
There are over 5,000 janitors in the U.S. with PhDs.
The PhD is not the highest degree a person can receive. There is also a Doctor of Sciences (DSc/ScD) and Doctor of Letters (DLitt/LittD) which is normally awarded in Britain, Ireland, and the commonwealth nations though it is occasionally awarded in the United States. It is normally awarded for a substantial and sustained contribution to the art to which it applies – for example science and literature. Mark Twain was awarded a Doctor of Letters by Oxford University. Just to add to the confusion, there is also a PhB which is a bachelor of philosophy which is equal to a Masters degree despite its name.