I was watching a Netflix documtary about killers, the guy said he was on drugs by age 9...so pretty sure that messed up his life before the murder. It is debatable on if surroundings or self choices are why you try drugs I guess.
Right, "should I do drugs?" is not a typical choice for a 9 year old to have to make, they should be protected from that. I have heard stories of particularly shitty parents giving drugs to their own young children.
9 year olds don't have "self choice" to use drugs.
Evem adults most often don't have it. Addiction starts with trauma, often in mother's womb. If mother is under stress while pregnant, huge and long stress, child has much bigger chances to become an addict.