The brain is plastic throughout life, but never more so than from birth to young adulthood. It increases its volume by developing dendrites and axons that connect neurons in to each other, forming new pathways to process the information that it will store. Those connections require maintenance. And if a connection is unsuccessful, better to delete it than to keep it. This is known as synaptic pruning and occurs from childhood to the age of 20. Now, a group of scientists from the University of Cambridge and Fudan University has described a neuropsychopathological (NP) factor that explains why inappropriate pruning in adolescence is related to mental health disorders.