Old Navy makes an important point. Well, several.
Everyone should be truthful about prior drug use because being honest is the right thing to do. That said, I'm not naïve enough to believe that everyone is going to own up to all of his/her "sins," especially if they fear that doing so could cost them an appointment.
Thus, Old Navy BGO and I are trying to let folks know that, if you aren't truthful, it likely will come back to bite you. First, if you have a problem with drug use, you may not realize it but, if you're honest about your usage, the Character Board probably will. If that's the case, you're better off not attending a SA as the likely outcome is an Other Than Honorable/Dishonorable Discharge. Or worse. If MJ is your thing and you can't kick the habit, you're better off someplace other than the military.
Also, as Old Navy points out, it may catch up with you eventually. Folks today post all sorts of things on social media -- if not you, the friend at the party who thought it funny to capture you high on MJ on her cellphone. And an investigator doing a security clearance finds it. Or finds your friend (as Old Navy said). And they find your paperwork where you said you never used. And you take a lie detector test (required for high level security clearances) where they ask if you've lied. And you say "no." Or maybe you now say "yes" (so were you lying then or now?) You can see how this whole thing could spiral downward in a hurry.
If you want to join the military, stay away from drugs -- MJ, spice, opioids -- any and all! If you did slip, learn from it and stop. And, when asked, be truthful about what happened.