A new study from the British National Academy of the Sciences has found that a critical substance increases in brain regions associated with depression and schizophrenia during adolescence.

Myelin, a fatty compound that coats neurons, allowing them to transmit signals faster, increases in many brain areas during the teenage years. However, its increase is particularly strong in areas associated with depressive and schizophrenic symptoms. The current study suggests that such an increase may partly explain why people often have first episodes of depression and schizophrenia during their teenage or early young adult life.

Ed Bullmore, a psychiatrist at the University of Cambridge, connects the study not only to the development of neurons, but also to a corresponding expression of mental illness genes: "it's during these teenage years that those brain regions that have the strongest link to the schizophrenia risk genes are developing most rapidly," he says.

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