May, Flavia SChen, Q.CeceGilbertson, MarkShenton, MarthaPitman, Roger2016-09-162004May, Flavia S, Q.Cece Chen, Mark W Gilbertson, Martha E Shenton, and Roger K Pitman. 2004. Cavum Septum Pellucidum in Monozygotic Twins Discordant for Combat Exposure: Relationship to Posttraumatic Stress Disorder. Biological Psychiatry 55, no. 6: 656–658. doi:10.1016/j.biopsych.2003.09.018.0006-3223http://nrs.harvard.edu/urn-3:HUL.InstRepos:28527471Background Abnormally large cavum septum pellucidum has been reported in posttraumatic stress disorder; however, the origin of this association is uncertain. Methods: We utilized magnetic resonance imaging to measure cavum septum pellucidum in pairs of identical twins discordant for combat exposure in Vietnam. Results: Presence of abnormal cavum septum pellucidum was significantly correlated between exposed and unexposed twins, indicating that it is partially determined by heredity and/or shared environment. There was a greater proportion of cavum septum pellucidum in combat-exposed twins with posttraumatic stress disorder and their noncombat-exposed co-twins. Conclusions: The presence of abnormally large cavum septum pellucidum is a familial vulnerability factor for posttraumatic stress disorder.en-USseptum pellucidumstress disordersposttraumaticmagnetic resonance imagingtwinsmonozygoticJournal Article2016-09-1610.1016/j.biopsych.2003.09.018