Of all the issues surrounding the question of substance abuse, this is perhaps the most controversial and emotionally charged. Many people see drug addiction clearly as a choice. And it may begin as a choice, but for some people, the choice is quickly lost.
Experimentation is always the initial step.
And this is the step most people understand. Part of being a teenager, growing up, is that feeling of being invincible. Teenagers feel that they will live forever. Parents accept that. For many, experimentation quickly moves into use.