From the Canada Lancet (1899), volume XXXI, no. 8, p. 1121:
Neuroses from Piano Practice — Dr. Wartzold (in Jour. d’ Hyg.) blames abuse of the piano practice for the chlorosis and neuroses from which so many young girls suffer. Girls, he says, should not be compelled to hammer on the keyboard before they are fifteen. He shows that of 1,000 studying the piano before the age of twelve, 600 were affected with nervous troubles; 200 of those who commenced at later age and only 100 among those who did not touch the piano.
Is it eye strain from staring at sheet music? Neurasthenia from strenuous memorization? Some sort of ebony-borne toxin? (“Chlorosis” is generally a disease of plants, not young ladies.) Chronic hand cramps leading to a morbid fear of the device, which would not arise in pianists whose hands had reached adult dimensions?
Dr. Wartzold’s original paper seems lost to history, or at least Anglophone history.
In Pleasure Wars: The Bourgeois Experience, Victoria to Freud (1998), historian Peter Gay suggests that instead of a causal link between piano practice and neurosis, both piano practice and neurosis result from life in a certain type of household.
[B]ourgeoisophobes incorporated the piano mania in their portrait of the uncivilized middle classes. It allowed them to condescend to petty bourgeois for aching to emulate their betters, and the prosperous for driving their daughters into neurosis. Actually many nineteenth-century private journals recorded delighted domestic music-making…
These pleasing scenes did little to reduce widespread disgust with parental aspirations and mindless practice sessions for tone-deaf young ladies. Music, complained the report of the English Schools Inquiry Commission of 1868, “is equally demanded of all girls, however little they may have taste for it.” In 1884, the English periodical Musical Opinion reported that there were no fewer than 424 German piano makers employing 7,834 workmen and turning out about 73,000 instruments a year. These impressive numbers would only have incensed Flaubert; respectable families found the piano, he cynically noted, “indispensable in a drawing room,” and did not cite love of music as a reason for making it indispensable.