Via Skepchick, here's a list of reasons that could get you locked up in a mental institution in the late 1800s. It purportedly comes from the former-known-as "Trans-Allegheny Lunatic Asylum," which is now open only for tours.
I could have been admitted for multiple reasons, although I won't divulge which ones ("novel reading" - really?).
It's notable that one could be admitted for "masturbation for 30 years" as well as for "suppressed masturbation." I guess the key was to find a happy medium.
In all seriousness, the list shows a sad, disturbing focus on sex, masturbation, and female bodies that perhaps said more about those categorizing and treating these patients and "illnesses" than about the patients themselves.
Anti-gay bigots like to bring up the former classification of homosexuality as a mental illness and claim that it was only due to pressures of the powerful gay propaganda that got homosexuality declassified as a mental illness. However, I think historical evidence like the above absurd list serves an important role in reminding us to question how homosexuality got framed as a mental illness in the first place.
A Conversation on the Word "Hysteria"