I don't know the actual studies Reallybadidea and I understand the difference between correlation and causation. But, others presumably have read the research and have formulated guidance on the basis of that.
There is no 'upside' to drinking earlier. Alcohol has no intrinsic benefits for anyone, and we know that it has a massively destructive effect on many, many lives as well. The knock-on effects on the country are devastating too - costing millions, making people unsafe in public places and putting both the drinker and those around them at greater risk of violent crime, causing massive health issues etc. etc.
Surely it is better to promote a culture of starting to drink later and drinking less. Like many people on here, I think it is impossible to predict who will go on to develop a dangerous relationship with alcohol, so it benefits all to follow advice that would help those more vulnerable. And by vulnerable, I don't think you can simply identify social issues associated with having problems later on.
Its not about making drinking taboo. There are age limits or guidelines for many activities, and I think information about alcohol and age should be more widely promoted, so it becomes the norm NOT to drink. Then there would be a greater consensus, and we wouldn't have the dilemma that this thread highlights. If people are going to drink - they have the rest of their lives to do it.
I realise this alone won't solve the problem, but I think it has to be part of the solution. The rest needs to come from government like in Iceland.
Their approach was radical and comprehensive - with lots of emphasis on encouraging kids to find natural highs etc. But it also included boundaries:
Laws were changed. It became illegal to buy tobacco under the age of 18 and alcohol under the age of 20, and tobacco and alcohol advertising was banned.
www.independent.co.uk/life-style/health-and-families/iceland-knows-how-to-stop-teen-substance-abuse-but-the-rest-of-the-world-isn-t-listening-a7526316.html