People with drug addiction can be treated and have a full recovery from the drug addiction if the person is determined to get off the drugs.
It can require over a year of drug treatment addiction classes to fully get over the drug addiction and still then some people who have been addicted to drugs for years can still have trouble getting off the drugs fully.
I had a friend who took 5 years of drug classes before he did get off the drugs and he's been drug free for over 5 years now.
I'm very happy for him because I thought he would die as a result of the drugs but he was bound and determined to get off the drugs.
Addiction also depends to some degree on the person taking the drugs and for soft drugs such as alcohol and marijuana.
And genetics plays a roll and If one or both of your parents is or was an alcoholic, you are more likely to have a drinking problem.
For hard drugs, no one is immune and other drugs including cocaine is powerfully addictive, and I understand that the same is true of meth and heroin.
If you do those, you will become addicted.
The best thing to do is to never get on drugs in the first place because once you do get on the drugs it can be hard to get off of them and they can kill you.