Your brain has 5 developmental phases, adulthood starts in 30s
27 Nov 2025

A new study has outlined five major "epochs" in human brain development, marking key shifts in neural wiring from infancy through old age.

By analyzing brain scans from nearly 4,000 people ranging from under one year to 90 years old, researchers identified four major "turning points" at roughly ages nine, 32, 66, and 83.

These stages reveal how the brain's overall organization changes across a lifetime.

From childhood to late aging
Developmental stages

The study divides human brain development into five broad phases.

The first phase, or "childhood," lasts from birth to age nine, after which it transitions into the "adolescence" phase that lasts until about age 32.

In a person's early 30s, their brain's neural wiring shifts into "adult mode," marking the longest phase of development lasting over three decades.

Early and late aging phases of brain development
Aging stages

The study also identifies an "early aging" phase of brain architecture starting around age 66.

This is followed by the formation of a "late aging" brain at about 83 years old.

The researchers measured various aspects of brain organization, such as wiring efficiency, compartmentalization, and reliance on central hubs or diffuse connectivity networks to understand these developmental and aging phases better.

Network consolidation and efficiency in brain development
Efficiency trends

From infancy to childhood, our brains undergo "network consolidation," where the number of synapses in a baby's brain is reduced with only the most active ones surviving.

During this period, the study found that wiring efficiency decreases.

However, gray and white matter volumes increase rapidly, leading to peak cortical thickness and stabilization of cortical folding, the characteristic ridges on the outer brain.

Refinement of brain's communication networks during adolescence
Communication refinement

In the "adolescence" phase, white matter volume continues to grow, refining the organization of the brain's communication networks.

This era is characterized by steadily increasing efficiency of connections across the whole brain, which is linked to improved cognitive performance.

The researchers clarified that their findings don't mean people in their late 20s will act like teenagers or have a teenage-like brain; it's more about the pattern of change over time.

Brain stability and compartmentalization after early adulthood
Post-adulthood changes

After age 32, the brain architecture stabilizes compared to previous phases.

This corresponds with a "plateau in intelligence and personality," as seen in other studies.

Brain regions also become more compartmentalized during this phase.

The final two turning points are marked by declines in brain connectivity, which are thought to be linked to aging and the degeneration of white matter in the brain.