How does drug use affect what we are like in the future?

I have just finished the book "exit here." by Jason Myers. I thought that this was a great book. I usually prefer to read fiction stories, but this one is completely different to those. This book is about the drug-related lives of these guys and the consequences of drugs. The main character, Travis Wayne, has returned from the worst vacation he's ever had. During this same summer his world is flipped upside down. I don't want to spoil anything from the book, so I won't say any more. This is a really good book that I would definitely recommend to any one that could handle the contents of the book.

When I finished the book, I realized, Travis's life was completely ruined because of drugs. That must really suck. How would you like it if your whole life was ruined, already at the age of 20 because of things that you really don't need, like drugs. You don't really think about these kinds of things until they really happen, but this book shows the horrible truth about drugs. It's something I'd never want to go through.

At the very end of the book I read the "About the Author". This, for me, was the worst part of the book. It said: "Jason Myers has lived the exit here life. This isn't a memoir, but Myers has lived close enough to guys like Travis to know how to tell the story right." Then, I had a horrible realiztaion that, you just can't make that stuff up, something very similar must have happened to Jason Myers or his friends for him to write a book like this. So, in what ways would drugs affect the people who do drugs? Would it change for the worst like Travis? Or, would the person mature and change for the better, like Jason Myers?