Brain Development in Early Adolescence May Signal Mental Health Risk Years Before Symptoms

The rate at which brain regions mature during early adolescence could help predict the emergence of mental health conditions up to four years before symptoms appear, according to a study of nearly 12,000 young people in the United States.

Researchers tracked young people’s brains across about 30,000 magnetic resonance imaging scans collected over six years. They mapped how the cerebral cortex, the brain’s outer layer, becomes thinner as children grow into teenagers.

The study found that sensory areas of the cortex matured first, followed by regions involved in complex thinking. Its findings were posted on the preprint server bioRxiv on October 11, ahead of peer review.¹

The results challenge the theory that mental illness is caused by defects in specific brain circuits. Instead, they suggest that vulnerability to mental health symptoms may be linked to disruptions in the brain’s developmental timeline. These disruptions could be set in motion by genes that are active before birth.

The study “provides one of the clearest pictures yet of how the cerebral cortex develops from childhood to adolescence,” says Abram Holmes, a systems neuroscientist at Rutgers University in New Brunswick, New Jersey, who was not involved in the research.

“It makes you think not only about location, but also about the timing of brain development,” Holmes says. When psychiatric symptoms are considered, he adds, the timing of changes in the brain may be important.

Holmes cautions, however, that the population-level patterns identified in the study are subtle. They become apparent only when data from large numbers of people are averaged and cannot yet be used clinically to predict the mental health trajectory of an individual child.

How the brain’s cortex matures during adolescence

During childhood and adolescence, the cerebral cortex becomes thinner. Neuroscientists believe this process is linked to the pruning of unused connections between neurons, which helps the brain operate more efficiently.

Psychiatric disorders such as depression are often diagnosed in late adolescence, when cortical thinning is beginning to subside. Researchers have therefore long suspected that disrupted cortical thinning could contribute to mental illness.

However, earlier brain-imaging studies often relied on small sample sizes or single snapshots of brain development. Those limitations made it difficult to establish the relationship between cortical thinning and mental health.

Study tracks brain development in nearly 12,000 children

To address these challenges, study co-author Jacqueline Kraus, a child psychiatrist at the University of Iowa, and her colleagues analyzed data from the Adolescent Brain Cognitive Development study.

The large project is tracking approximately 12,000 children around the age of nine. Participants’ brains are scanned every two years, while their parents complete an annual survey about their children’s mental health symptoms.

The researchers found that brain regions do not thin at a constant rate. Instead, they change along distinct developmental trajectories that follow an S-shaped curve: cortical thinning initially accelerates, then progresses steadily, and finally slows as each area approaches maturity.