I have a friend who has taken some flight lessons, and has some interest in being a pilot, has the money if they can find the time.

However, one big issue: due to a long time physical problem,. since a teenager, that causes pain and wakes him about every 3rd night, he has gotten a licence, (it's state legal) and uses medical marijuana. He is not sure if it is going to help him, he's only been using it a month or so. And his pain is not like the classic cancer case, it doesn't bother him in the daytime, only wakes him up often with body aches when he tries to sleep. He can work, but does take off some sick days when he can;t sleep.

So, 2 questions:
1. How long does it take for all mj to leave his system if he decides to quit using it?
2. What is the FAA position on previous mj use if and when he quits and decides to go on with pilot lessons?
Obviously one can't and shouldn't fly if under the influence at all, and the mj dispensary says not too drive within 6 hours of using. But you can get blotto drunk and recover and then lay off for a day or two and then be perfectly legal to fly, should mj, which is obviously less debilitating, be different?
I don't think there is any real good factual research on this, like a blood level of alcohol of say .05