In an appendix to On The Writing Of The Insane, G. Mackenzie Bacon notes the similarity between the writing of the insane and the writing of the lower orders.

In the position I occupy I receive a good many letters from the poorer class, and have often had from some of my correspondents very odd specimens. The three following [which you can consult at the Public Domain Review] are from individuals belonging to what is called the sane portion of the public. In [one] the contrast between [the] style and those in the preceding pages [by certified lunatics] is perhaps not so well marked as one would like to expect.