Key points from article :
Researchers have mapped five major “eras” of human brain development, showing that the brain does not mature in a smooth, continuous way but instead shifts through distinct phases marked by sharp turning points. The study, led by Alexa Mousley with senior author Prof Duncan Astle at the University of Cambridge, analysed almost 4,000 brain scans from people aged under one to 90. The work, published in Nature Communications, identifies key transitions at approximately ages 9, 32, 66 and 83.
The first era, from birth to about nine years, is defined by rapid synaptic pruning and consolidation of neural networks. During this time, grey and white matter expand quickly, cortical thickness peaks, and the characteristic folds of the cortex stabilise. At nine, the brain enters an adolescent phase that extends unusually far—up to around 32 years. This period is marked by continued white-matter growth and steadily increasing efficiency of brain-wide communication, matching improvements in cognitive performance. The authors stress this does not mean people in their late 20s have “teenage brains”, but rather that the pattern of internal reorganisation continues.
Around the early 30s, the brain undergoes its strongest shift: connectivity patterns stabilise, regions become more compartmentalised, and the brain enters a long “adult mode” that lasts for more than three decades. Life milestones such as parenthood may contribute to these changes, though this was not directly tested.
The final two transitions, near 66 and 83, signal early and late ageing. These eras are characterised by declining connectivity and likely reflect the gradual degeneration of white matter. By identifying these neural turning points, the study offers new clues about when the brain is most vulnerable—and when mental health conditions or age-related decline may be more likely to emerge.
