Other variations in the same gene and in other genes have been linked with PTSD in previous research. But the new research was unique because it involved 204 undergraduate women who by coincidence were taking part in a campus study that measured stress before the shootings on Feb. 14, 2008 - so before-and-after information was available.
The shootings occurred in a crowded lecture hall on the NIU campus in DeKalb, about 65 miles west of Chicago. A former NIU student opened fire, killing five and wounding more than a dozen others before killing himself. Most study participants were on campus at the time.
Overall symptoms similar to PTSD were found in almost half the women in the weeks after the shootings, and in nearly all the participants who were in the hall. These symptoms included flashbacks, nightmares and extreme jumpiness.
Information on stress symptoms in the women that had been gathered before the shootings helped the researchers better assess what role their genetic makeup might have played in how they reacted to the violence, said Kerry Ressler, of Emory University and the study's senior author.
The study was released yesterday in the September edition of Archives of General Psychiatry.
The researchers analyzed genetic material in saliva samples that women submitted after the shootings. The women also filled out questionnaires commonly used to assess PTSD and related symptoms, at two times after the shootings - two to four weeks afterward, and then an average of eight months afterward. By definition, PTSD persists for more than a month, but similar symptoms can develop soon after traumatic events.
The variations in the serotonin gene were found in 25 percent of the women studied. Overall, 52 percent of women with those variations developed early or later PTSD symptoms, versus 43 percent of women without the variations.