Coffee, chocolate, and sugar are drugs. If a drug is a substance that affects how your mind functions, then water is a drug too. There is no definition of "drug" that cleanly separates the (currently) illegal substances from those that are legal.

The world is full of chemicals that affect us, some more than others. People self-medicate all the time (alcohol, coffee, chocolate, sugar); I see no problem with (after learning and carefully experimenting) broadening one's set of "self-medication" tools.