New research seems to suggest that despite 18 being the legal definition of being an adult, humans do not fully develop into adulthood until they are in their 30s.

According to a report by the BBC, brain researchers in the United Kingdom say that people over the age of 18 are still going through changes in the brain which can affect behavior and make them “more likely to develop mental health disorders.

Professor Peter Jones, from Cambridge University, told the BBC, "What we're really saying is that to have a definition of when you move from childhood to adulthood looks increasingly absurd…It's a much more nuanced transition that takes place over three decades."

In the United States, people who are 18 years old can vote and sign up for the military. But they cannot purchase alcohol or tobacco products until they are 21. And in some states, adults are not allowed to rent a car until they are 25 years old, without some provisions.

So what makes someone an adult?

“It depends on what you’ve gone through in your life,’ says Jeremy Hidalgo of Passaic. “Some people mature earlier than others because of everything they’ve been through.”

Carol Bond of Piscataway says, “When you can pass that stage when you’re on your own and you’re responsible, then you’re an adult.”