Consider one thing. One that IS key in security clearance, as it IS all about TRUST.
Lying would torpedo you. Period, end of story. Being honest and open is big in this game, lest you be a potential blackmail victim that could then be leveraged against the nation.
Or, so the mindset thinks. Personally, I think it’s a blanket ignoring spectrum, but it’s a least effort mentality and hence, valued, due to pure volume of requests.
Confidential clearances, in the clearance world, are pretty much given out like candy, as opposed to secret or top secret (ignoring alphabet soup sub-qualifiers).
What the investigator would consider is, was the drug use a month ago, six months ago, a year ago or longer, ad absurdium.
Self-reporting carries a positive weight in the evaluation.
But, in TODAY’S world, prior drug use of “gateway” drugs in the relatively recent past (as in college graduate) isn’t highly negative, as opposed to dishonesty or harder drug use and OTHER risk prone behavior (see the recent Secret Service Protective Service debacle for more risk prone behavior idiocy).
Or to be blunt, ALL consider an applicant a pot smoker, “didn’t inhale” is BS, as all really know. Hence, risk is OTHER behavior that might create a risk.
As in heavily addictive drugs (narcotics, amphetamines and a small handful of others), GENERAL behavior (patronizing prostitutes, excessive sexual indiscretions, etc).
Or most telling: I drink like a fish, previously used and disliked communism (important when I got my clearance initially), but got a TS with alphabet soup clearance and retained it for three decades.
I know pot smokers who self-reported previous use and got cleared initially and subsequently.
Confidential is a nothing much clearance, it’s BARELY above For Official Use Only (aka FOUO, which is NEARLY public, but not quite).
I’ve oversimplified it by a lot, but the intent should be relatively clear, as far as clearance matter things go.
BTW, one responder said 7 years, that is for TS, not S or C clearance, which use 5 years as a benchmark, when flags aren’t present. But, I’ll not go into flags. It’d get ME into trouble and for good reason.
IN short, self-report. You’ll not be in as big of a problem than if you tried to hide that which may well be easily found.