In preliminary studies of childhood onset of schizophrenia, investigators have found fall off of the growth curve in the frontal and temporal lobes in over 50 children studied thus far. They have shown on serial MRI's an actual drop in the volume of the frontal temporal lobes that occurs in early to mid-teenage years in these children. This question comes from Rebecca Hudson. I think violence has several roots, and I think gender differences come into play because boys tend to have more societal modeling of aggressive or acting out behavior. There is probably a genetic or sex bias based on hormonal influences on brain activity.
Boys tend to have more neurologic abnormalities than girls, generally.
They have a higher frequency of diagnosis of certain conditions such as Tourette's syndrome, ADD, and some learning disabilities. So there may be more genetic or brain based vulnerability in boys. For example, apart from the increase in physical violence there seem to be more verbal put-downs and teasing, as a routine form of interaction. Presumably these chemical changes could lead to depression in a susceptible individual. There may be a role for that mechanism of influence on the brain.