I just wanted to point out that obtaining a security clearance is not nearly as hard as you make it sound. For most organizations prior recreational drug use does not preclude you from the clearance.
A lot of what they look for is consistency in accounts of previous behaviors between you and any references / interviews they undertake, trying to assess if you're currently honest.
Another big thing they are trying to decide is if you are blackmailable.
(throwaway because I have the sort of clearance you are not supposed to advertise that you have)
(clearly decades ago, and he's less than reliable, but fun nonetheless!)
It's a problem if you do drugs and are hiding it from someone (say, family). Then you can be blackmailed.