Appearance and demeanor have a lot to do perception of age. If you dress like your 16-22 and have similar mannerisms people will often mistake your age. Obviously physical attributes play a role, especially face shape.
It would seem that people who do drugs often get "stuck" in the time they started doing them. Since they dont evolve their style, change associations, or general location they get stuck in a cycle of dressing and acting the same due to lack of exposure "normal people" experience. It is usually hard drug use that causes this effect as it is hard to change anything about your life, even appearance, when the whole existence revolves around trying to get and maintain a drug supply.
This is just my observation because i would venture to guess, no drugs do not help you age well. Constantly being malnourished and lacking true sleep cant be good (depending on person and drug of abuse this will vary)