poor medical practices taking place in the medieval times i.e. drilling a bore hole into someones head to fix mental health issues

Trepanning is a perfectly legitimate medical procedure even today. u/BedsideRounds shows some signs where Ancient doctors would recommend trepanation. A search on PubMed for 'trepanation' shows a mix of historical articles and reports on aspects of trepanation as a medical procedure.

As for how effective the other procedures are? As always, It Depends, but we can safely say "better than most people expect". I shall copy the appropriate bit from my Middle Ages Are Best Ages Compilation:

• In addition to the above post, BedsideRounds also has a non-exhaustive list of Stuff That Worked;
• u/sunagainstgold talks about medicine and its efficacy, as well as medical education in the Late Middle Ages;

But the star of this post is u/BRIStoneman drawing from the 9th Century medical text Bald's Leechbook:

• On the book's attitude to the treatment of medical conditions in general;
• On the treatment of infected wounds;
• On its recommendations for cuts and fevers (with bonus literacy downthread);
• And an assortment of treatments demonstrating that the leeches of Early Medieval England were on to something.

Bonus: Bald's Leechbook is available in all its digitised glory here.

As always, if anyone would like to contribute further any knowledge about Medieval medicine and its effectiveness, please don't let this post stop you! More posts are always welcome.