Science Says This Age Is When We Actually Become Adults

With all the scientific advancements that continue to increase our quality of life, sometimes we forget how much the human lifespan has dramatically risen in recent history. As The Gerontologist notes, the average human life expectancy in the U.S. was only 47.3 years in 1900. Before this, we know that cavemen rarely lived past 30. But now, per 2024 data published by the Centers for Disease Control and Prevention (CDC), the average life expectancy is now 79 years. With these statistics in mind, one could assume that humans spend most of their years in adulthood phases of their lives. While true, the exact phases may be further apart than originally thought. Scientists have flipped this script in recent years, with some theories suggesting that adolescence may actually go much further than 18 years old several years due to the process of brain maturation. The latest theory from a group of neuroscientists from the University of Cambridge argues that people may not technically be considered adults until 32 years of age!

The link between true adulthood and the age of 32 stems from a landmark study published in 2025 in the journal Nature Communications. Here, the aforementioned University of Cambridge neuroscientists report findings from the brain scans of 3,802 people from infancy through age 90. Based on the results, the authors concluded that the age of 32 marked one of four key changes the human brain experiences among five phases: Childhood, adolescent, adult, early aging, and late aging brain. They identified ages 0 to 9 as childhood, and adolescence beginning after this point and lasting until about age 32. Adulthood lasts from 32 until 66, then the next phase shifts into "early aging" from 66 to 83. The last major turning point occurs around age 83, which the researchers describe as "late aging" of the brain.

The results of the Nature Communications study certainly prompts further reflection about how the brain develops throughout a person's lifetime. To that end, it's important to keep in mind that this age and adulthood correlation from this particular research is meant to highlight changes in the brain. It does not mean that you are not capable of "adulting" until the age of 32 (hopefully!), nor does it necessarily insinuate a lack of maturity until your early 30s. 32 is also an average, so you won't see a sudden switch in someone who turns this age. Furthermore, it's unlikely that our culture will reclassify adulthood as being 32 from where it stands at 18 years old in almost every state. Yet we can take these results to help us understand strengths and weaknesses in the brain within the different phases, as well as what the brain might need to help keep it healthy at various points in time. It also points to the need for a more complex approach to how we understand aging.

If you believe in the old adage that "age is just a number," you can take heart knowing there are other measures of age beyond these brain scans. For one, it's worth remembering that new brain cells form at all stages of life through a process called neurogenesis. This is also among the key anatomical facts about the brain that might surprise you. So while the brain might change in functionality with age, it is possible to slow down the process through cognitive and physical exercises, stress management, and socializing. Some of these same activities might also benefit your physical health, too (and it's worth noting the human body starts aging faster once you reach your 50s).