If a doctor does it, pressure is relived and everything is alright. Anyone else does it and it will probably kill you.

Although some people believe that it will expand their consciousness through increased blood flow to the brain, one person who went through the procedure said:

"come to the frustrating conclusion [four weeks after the procedure] that the trepanation has had no lasting effect… Trepanation has no more physiological effect than any other trauma… it does not do what many hope it will."

Read more about trepanation and self-trepanation in the link below.