I'd heard of the writings of Dr. Samuel-Auguste Tissot, but I had no idea his 1760 book on masturbation was still in print! The 2015 edition of Diseases Caused by Masturbation was originally titled L’Onanism. Dissertation sur les maladies produites par la masturbation.
The book recounts stories from his own patients and from the patients of other renowned European doctors to support his claim that masturbation is deleterious to a person’s body and mind. Tissot also uses quotes from the ancient physicians, such as Galen and Celsus, as well as the most noted doctors of his day, such as Herman Boerhaave, to further strengthen his claim.
It's pretty easy to see how he might come to those conclusions. First off, everyone who went to the physician for treatment had a physical illness. Secondly, not only did everyone masturbate, in the 16th century most of them felt guilty about it, and it was easier to confess to the doctor than to the priest. The correlation was clear. You can read quite a few pages of the book, but the reviews are the best part of the Amazon page, even though most reviewers admit that they have already gone blind. Now I can look forward to weird contextual ads following me around the 'net. It's an occupational hazard. -via Blame It On The Voices