There's been quite a lot of discussion of this problem here over the years. While there's always more to say, you might find it interesting to review these earlier threads while you're waiting:

On Hitlers "feel good" doctor who kept him on his supposed even keel, led by /u/CommieSpaceInvader

Was Hitler taking any medication for his 'shaking' (suspected Parkinson's) If so to what extent did this affect his decision making/planning?, led by /u/estherke

There are also older (read: less extensive and well-cited) discussions relating to your question here:

Is it true that Hitler became severely addicted to drugs toward the end of WWII?, led by /u/DoctorWhoToYou

When did Hitler's drug use begin?, led by /u/impossible_planet