Stepping into your 30s? New study reveals you may still be an adolescent

The findings may help us comprehend why the risk of dementia and mental health issues fluctuates throughout life. The brain is always evolving in reaction to new information and experiences, but research indicates that this is not a single, seamless pattern from birth to death.

Due to the large number of brain scans available in the study, titled ‘Topological turning points across the human lifespan’ which was published in the journal Nature Communications this month, these patterns have only recently come to light. While some people will reach these landmarks sooner or later than others, the researchers said it was remarkable how clearly these ages stood out in the data.

The five brain phases:

• Childhood – from birth to age nine
• Adolescence – from nine to 32
• Adulthood – from 32 to 66
• Early ageing – from 66 to 83
• Late ageing – from 83 onwards

“The brain rewires itself across life,” the research’s principal author, Dr Alexa Mousley, told the BBC, adding, “There are fluctuations and phases of brain rewiring, and it’s not one steady pattern. It’s always strengthening and weakening connections.”

The five brain phases

Childhood marks the initial phase of brain development, characterised by a rapid increase in brain size and a simultaneous thinning of excess synaptic connections. During this period, the brain’s efficiency diminishes, likened to a child exploring a park without a clear path. A pivotal change occurs at nine years of age, as the brain transitions into adolescence, where it becomes remarkably more efficient in terms of neuronal connections. This phase, beginning with puberty, was previously thought to conclude in the teenage years, but recent neuroscience indicates it may extend into the mid-30s.

Adolescence is linked with a peak in brain functionality and a higher susceptibility to mental health disorders. Following this, the brain enters adulthood, a stable phase that lasts approximately 30 years during which cognitive growth slows down; efficiency begins to decline, and cognitive plateauing occurs, mirroring stability in intelligence and personality traits that are often observed in this life stage.

As individuals approach early ageing around 66 years, brain connections undergo shifts toward increased regional specialisation, resembling band members pursuing solo careers rather than collaborating. This phase also coincides with a rise in age-related health issues such as dementia and hypertension, affecting cognitive health.

The final stage, late ageing, begins at 83, exhibiting even more pronounced changes as compared to early ageing, though data for this phase is less comprehensive due to challenges in studying healthy brains. Notably, this research underscores the alignment of developmental brain stages with significant life milestones, including puberty and transitions related to health and social role changes in early adulthood.

Compelling demonstration of what the brain undergoes

The study examined brain changes over a lifetime but did not differentiate between genders, leading to potential questions about factors such as menopause. Duncan Astle, a neuroinformatics professor at the University of Cambridge involved in the research, emphasised that neurodevelopmental, mental health, and neurological conditions are closely related to brain structure. He noted that differences in brain wiring can predict various behavioural challenges, including those related to attention, language, and memory.

Prof Tara Spires-Jones, director of the Centre for Discovery Brain Sciences at the University of Edinburgh, described the research as a compelling demonstration of the significant changes the brain undergoes throughout life. She pointed out that while the findings align with established knowledge on brain ageing, there is variability in the timing of network changes among individuals.