Question about former drug use and depression...

Long story short, I REALLY want to be a nurse, can't really think of anything else "fitting" for me. But, I have a friend that keeps telling me to forget it because, in my past, I had an issue w/ drug abuse and depression. I was getting very depressed and turned to pills to get a "high" and make myself feel better. Now, I was never involved in anything criminal, meaning I've never been arrested for anything... I have NO criminal record. I realized the problem by myself and sought help through counseling by myself. Does this mean I won't be able to get into school or what about getting a job after that? Is my medical history ever going to be relevent or looked into? I live in Canada but, I'm american so I'd like advice on the "workings" from either country. I may go back to the states eventually. Thanks in advance, any input will be greatly appreciated.
Without attempting to give any legal advice imvho I don't think someone without a criminal record needs to disclose anything private about their past if they want to become a nurse. FWIW most of us were not Girl Scouts and made plenty of mistakes of our own during our teenage and young adult years that we learned from and moved on. I'd suggest you to go for it and congratulations on doing the work necessary to get your life straightened out.
If people needed perfect pasts to enter the profession of nursing, about 80% would find themselves out in the cold for one reason or another. You are interested in becoming a nurse today, not in the past. What is relevant today is your ability to handle the situation as it is today. As long as you can manage your life within lawful parameters and common sense, no one should be digging in your past to disqualify you. So don't live in the past. Good luck with your future plans.