File photo: The condition results in the disintegration of brain tissue due to an enzyme deficiency, which eventually leads to the build-up of toxic levels of sulphite in the body.

London - If you know someone who behaves immaturely, have patience – their brain could still be developing.

A study backs the idea of the “eternal adolescent”, whose brain evolves long after it was thought of as hard-wired.

Advanced brain mapping reveals that structural changes in white matter – the brain’s wiring – occur for at least three decades.

The brain is at 90 percent of its full size by the age of six but different parts, or tracts, continue developing in young adulthood.

Scientists used imaging to investigate white matter connections in 403 healthy volunteers aged between five and 83.

They discovered an increase in white matter post-adolescence, which reached a peak between 20 and 30 – and in some cases continued beyond, the journal NeuroImage reports.

Professor Christian Beaulieu, of the Department of Biomedical Engineering at Alberta University, Canada, who led the study, said it was the latest in a series showing the brain does not stop developing in adolescence.

He added: “It seems we are laying down highways for the first 25 to 30 years and then the gains go negative. It doesn’t mean you’ve forgotten how to drive – we lose some capacity but some parts of the brain work much better.”

The study could help scientists understand what can go wrong with brains as they get older. - Daily Mail