I have ADD, and mild ADHD which are both forms of the exact same thing. It definitely exists and it definitely has given me a hard time in a lot of settings throughout the course of my life.

For myself atleast, cannabis completely 100% takes care of my ADHD(the hyper active crazy shit I do), but my ADD seems to be enhanced when I'm high. I have almost literally no short term memory, and my ability to focus on one thing for more than 30 seconds is just gone. Like, goooone.

Other than that I suffer from anxiety, but I only get it when I smoke ciggs now, which is all the time, so I've been cutting back a lot.

Honestly I think people who have anxiety, and perhaps more serious mental illnesses are attracted to cannabis as some form of balance. I know when I have anxiety the first and utmost thing I want to do is get baked as hell. It definately help at first, but later on... I dunno, just keeps coming back.