The human brain goes through five phases, with adolescence lasting until age 32: study

The adolescent brain epoch last from approximately ages nine to 32. (University of Cambridge)

The human brain goes through five distinct phases, with the adolescent period lasting until our early 30s, according to a new study.

Based on MRI scans of 3,802 people ages zero to 90, researchers found that these five “major epochs” in brain structure are divided by four distinct “turning points” when our brains reconfigure around ages nine, 32, 66 and 83.

While these turning points may occur earlier or later in some people, the five brain eras were consistently observed throughout the study.

Published Tuesday in the academic journal Nature Communications, the study was led by neuroscientists from the University of Cambridge.

“We know the brain’s wiring is crucial to our development, but we lack a big picture of how it changes across our lives and why,” lead author and University of Cambridge researcher Alexa Mousley said in a news release. “This study is the first to identify major phases of brain wiring across a human lifespan.”

Childhood brain – zero to nine

The first brain epoch lasts from infancy through childhood. This is a period of “consolidation” in which an abundance of synapses – which connect neurons – are whittled down. At the same time, white and grey matter – which process and transmit information in the brain – grow rapidly in volume.

Adolescent brain – nine to 32

The second brain epoch lasts from approximately age nine to 32. In this period, our brains become more efficient and cognitive performance increases while white matter continues to grow in volume.

Mousley says this era “is the only one in which this efficiency is increasing.” It ends around age 32 with the largest turning point in our brain development.

“While puberty offers a clear start, the end of adolescence is much harder to pin down scientifically,” Mousley added. “Based purely on neural architecture, we found that adolescent-like changes in brain structure end around the early thirties.”

Adult brain – 32 to 66

Lasting over three decades, the third epoch is the longest. In our early 30s, our brains enter adulthood as brain architecture stabilizes, leading to a “plateau in intelligence and personality,” according to the study.

Early ageing brain – 66 to 83

While there are no major structural changes to the brain that occur around age 66, the fourth epoch is marked by “reduced connectivity” as white matter begins to degenerate.

“The data suggest that a gradual reorganization of brain networks culminates in the mid-sixties,” Mousley said. “This is an age when people face increased risk for a variety of health conditions that can affect the brain, such as hypertension.”

Late ageing brain – 83 to 90

The fifth and final epoch begins around age 83 as brain connectivity declines even further.

“Looking back, many of us feel our lives have been characterized by different phases,” co-author and University of Cambridge neuroscientist Duncan Astle said. “It turns out that brains also go through these eras.”