Original sentence: There is evidence that traumatic stress causes notable changes in brain functioning and development   Furthermore, children who have been sexually abused show measurable negative changes in brain functioning and development  A study by Mark Gilbertson indicates that preexisting conditions may make one more vulnerable to trauma
Edited sentence: An extensive literature review by Harvard Professor Richard McNally indicates that nongenetic explanations for changes in brain functioning are improbable.There is some evidence that traumatic stress causes notable changes in brain functioning and development   Furthermore, children who have been sexually abused show measurable negative changes in brain functioning and development  However, a recent study by Mark Gilbertson have shown that trauma may not be the cause for damage but that preexisting riskfactors may increase the risk for developing PTSD.This is supported by studies which show that those who have shown damage also have a history neurocognitive abnormalities