The recent murders of Rob Reiner and his wife allegedly by their son, while shocking, raise critical issues on addiction and parenting. Contrary to popular belief, addiction is not genetic but caused by the lack of a "good enough" though not "perfect" parenting which none have. The early life parent-child interaction enables the child to develop basic ego capacities including the ability to control thinking and behavior, modulate mood, and develop a sense of self (sense of who they are).
Substance abuse begins during adolescence though, rarely, it can begin earlier or later. Its motivation is the stress encountered when the troubled adolescent tries to cope with its normal challenges: becoming provisionally independent of their parents; deciding their educational and vocational future; and dealing with the powerful feelings aroused by dating. A teenager who isn't ready to fulfill these tasks will experience painful stress that some try to relieve with drugs or alcohol. Thus using drugs or alcohol simply reflects the attempt to feel better despite its associated legal and psychological harm.
The treatment needed to replace deficient ego capacities with more mature ones is not simple or quick unlike the addictive substance that grants relief. I have known teenagers who experienced many rehab experiences before turning their life around, particularly since many are poorly staffed and theoretically suspect. Media have documented some with practices resembling a concentration camp. It's a Wild West for parents seeking quality treatment for their troubled or addicted teenager.