A study of college students' reactions to shootings on their Illinois campus gives fresh insight into how genes may influence the psychological impact of traumatic events.

The researchers found that symptoms similar to post-traumatic stress disorder (PTSD) were more common in Northern Illinois University students who had certain variations in a gene that regulates levels of serotonin, a brain chemical linked with mood that is the target of popular antidepressants.

The results could someday lead to new treatments for PTSD. They also could help predict who will develop the condition, which could be useful for soldiers involved in combat.

The study was released in the September edition of Archives of General Psychiatry.

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.

Variations in the same gene and in other genes have been linked with PTSD in previous research. However, this new research was unique since 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.

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 Dr. Kerry Ressler, an Emory University researcher and the study's senior author.

The researchers analyzed genetic material in saliva samples 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.

First of all, it was filled two to four weeks afterwards. It was again filled 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 university set up special counseling services after the shootings that are still available since many students on campus in 2008 remain enrolled at NIU.

The hall where the shootings took place is being remodeled, and a memorial sculpture to the slain students has been set up nearby.