I've certainly noticed that every time new laws are passed restricting young people, a few years later a study is published showing that the brain doesn't mature until even older. I'm not sure which way the causality runs, but I've definitely seen the supposed age of brain maturity rise from 18-20 to 22 to, nowadays, 25.

Which means that apparently by the time my brain actually matures next year, I'll have been able to vote for 7 years, hold all legal responsibilities for 7 years, drink legally for 7 years (outside the USA) and 4 years (inside the USA), and apply for a driver's license for 9 years. I'll have actually lived outside my parents' home for 7 years, been in a single steady relationship for 6 years, supported myself financially for 3 years and held a driver's license for 2 years.

Apparently my legal qualification and actual, demonstrated ability to behave like an adult - all of which is actually pretty normal for someone my age whom I know - either demonstrates unusually precocious brain maturity, or doesn't actually require brain maturity, or these "studies" are showing the effects of society's treatment of young people as barely-functional retards for ever-more-extended periods.