There was a brief fad of trepanning in the 70s. People thought it might be a cure for depression, or might have wanted to experience the divine. It was mostly self-trepanning, with awls or electric drills. [1]

[1] https://www.washingtonpost.com/archive/lifestyle/1998/05/31/...

Wait, so does it have noticeable effects on consciousness? I wish the article had described the perspective of patients. What does it feel like?

If you're interested there are articles about people who tried themselves or with the help of friends at home, in the 70's or so. I read about it a while ago, but although it's an interesting read there's no clear answer (people were already into it enough to perforate their own skulls, so their account isnt very subjective, and they were usually into the paranormal, "energies" and similar pseudoscientific ideas).

A great Manga with a premise centered around trepanation is Homunculus by Hideo Yamamoto

I guess this is my cue!