Are Sherlock's addictions good for his mental condition? I noticed he avoids alcohol (rarely drinks), but used to smoke (still does, on occasion) and does / did drugs. As if drugs and cigarettes helped him to be "smarter/ better, etc", so this is why he decided to choose them (among other addictions).
"What do you get for the man who has everything?"
This is frequently said of those whose wealth prohibits his friends from buying gifts.
Holmes' wealth is sheer intelligence. A man with boundless money could go mad because acquiring possessions only fleetingly will make him happy. Holmes, on the other hand, is left a prisoner to the musings of his mind.
It's understandable that he would rarely take a drink; alcohol is a depressant, and leaves a man tired and thinking slow. Nicotine on the other hand is a stimulant. This would get his mind racing to places he might not otherwise. And opium is ratcheting the high to highest levels, causing euphoria and hallucinations. These are the vices of a man who has everything.