Garza K, et al. - In this review, the physicians investigate the recent literature on biological factors that affect sex differences in posttraumatic stress disorder (PTSD) during childhood and adolescence, focusing on neurobiological, hormonal, and genetic factors that may increase risk in girls. They reveal that the literature on gender effects is still in the early stages, and more prospective and longitudinal work is required. However, in girls, estrogen seems to play a key role in increasing risk for PTSD, which emerges in adolescence.