You never can tell beforehand how a psychiatrist will respond to drug use. Some of them completely believe the propaganda, and some of them actually know what's what, and will give you a minimum of hassle over something like weed. Most will try to convince you to stop drinking and taking whatever you're taking, especially if they prescribe other medications. That has more to do with minimizing variables than anything.
Lots of people take drugs as a form of self-medication, try to bend their mind into a more pleasing shape. Sometimes it works, and sometimes it's a fucking disaster. I drink, heavily, during social functions, because it's (for me) a better anxiety treatment than anything I've ever been prescribed.