Jeremy, I imagine you will receive many answers to your question. I am simply going to tell you it doesn't.
Drug abuse is a symptom.
Anyone who argues any differently is blowing smoke up your ass. As for what the symptom is from, that is subjective to the individual. It is easy to label the drug use as the problem rather than the symptom it is because the real problems are very complicated. Substance abuse will subside when the underlying problems driving it are dealt with and not a moment sooner. That said, I also believe there are a lot of well intentioned people out there trying to help who work really hard to help people.