""Your brain isn't fully formed/you're not really an adult until age 25" is not really supported by neuroscience - and this factoid is doing harm to people. We need to drop it."

And not only that, but it's perpetuated by amatonormativity and cisheteronormativity that dictates that if you're waiting longer to get married and/or have kids--or if you're not doing it at all--that you're not "growing up."

https://slate.com/technology/2022/11/brain-development-25-year-old-mature-myth.htm