Can the recruiters fund out if you smoked weed

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I’m 18 yo thinking bout joining. My main concern is if they can find out if you’ve ever smoked pot. I’m not a heavy user of that stuff but when i was like 16 I admitted to a doctor. And I still have no idea if they ever wrote it down on a record somewhere. Should i just be honest and tell them or can i just lie. I feel like lying could work so correct me if I’m wrong