"For all intents and purposes" sort of already implies something along the lines of "ignoring the obvious differences, etc" in the same way that 30 year olds and 50 year olds are both adults despite the age difference.
That was not what I meant in my original reply. Teenagers' brains are different from that of an adult - different in a way that a 30-year-old and a 50-year-olds brains are not different.
So, to be clear, the original claim was that teenagers are adults minus the experience. That claim is demonstrably not true. See http://www.npr.org/templates/story/story.php?storyId=1241194... or any other story that pops up when you Google "teenage brains."
