Using thermochromic paint to cover the type. I would use the ink to create small the type so it looked like the word on a page. The word would disappear and underneath it would reveal the equipment used or things that describe the word.
the word would either be the a treatment that they used to use or the mental disorder.
Underneath the type would be illustrations relating to the word. They could be quite large to be revealed under each word. Like the instruments used in trepanation.
Or there could be small illustrations that could be shown so its not obvious at first that the little illustrations represent what the word is so you have to look closely.
The paint works well with the concept because it hides what’s behind the type, and mental disorders are a very hushed topic that not many people want to discuss. The hidden illustration almost show the truth behind mental disorders and how they are treated.