However, a new study (albeit not exactly a new idea) strongly implies that at least much of the observed association between earlier age at first use and greater likelihood of addiction is actually due to reverse causation. That is, kids who were at greater risk of addiction actually showed measurable brain differences compared to those who weren't, even before they took their first sip or puff. This is truly a paradigm-shifting study indeed, and one that will require everyone to fundamentally rethink their approaches to prevention.
That is NOT to say that using substances at an early age (especially before 15) is actually a wise idea, of course. It still appears to be at least somewhat riskier overall, and the results of twin studies (which completely control for genetics, and largely control for environment) of the past still have yet to be completely explained away. But this latest study shows that the reality is far more nuanced than meets the eye, and that "delay, delay, delay that first drink or use at any cost!" is also probably not the wisest approach to prevention either. And, of course, the 21 drinking age (and smoking age and toking age) now has even less support still from The Science.
Perhaps this why Denmark and Iceland, who each take diametrically opposite approach to teen drinking (i.e. very permissive vs. very restrictive, respectively), still ultimately end up with remarkably similar alcoholism rates among adults. Just like the USA vs Canada, basically.
