Researchers at the University of California in Los Angeles have located two genes involving serotonin production in the brain that increase a person's risk of developing post-traumatic stress syndrome (PTSS). Previous studies have also linked serotonin levels to PTSS. PTSS is a debilitating psychiatric condition that can develop after a life-threatening event. Symptoms can be flashbacks, emotional numbness, problems in anger management and relationships, hypervigilance to danger, and avoiding situations reminiscent of the original trauma. The federal government is funding many new studies of PTSS because so many veterans of the conflicts in the Middle East are returning home with the diagnosis, and because the number of suicides among veterans is now equal to the number killed overseas. One aspect of PTSS that puzzles researchers is why one individual develops the syndrome and another does not, after both experience the same traumatic event. The answer seems to be in the individual differences in how people processes serotonin in their brains, and the genetics behind that process. Since serotonin is a brain chemical that regulates mood, sleep and alertness, and since PTSS disrupts all three, the UCLA research team hypothesized that this chemical may be involved in the development of the syndrome. Dr. Armen Goenjian of the Semel Institute for Neuroscience and Human Behavior at UCLA and his colleagues took DNA samples from 200 adults who developed PTSS after the 1988 earthquake in Armenia. The participants were from 12 extended families and included several generations. Participants who had specific variants of two genes called TPH1 and TPH2, which control serotonin production, were more likely to develop the psychiatric syndrome after the earthquake. Dr. Goenjian believes that the two variants could account for about 8% of the variance in severity of PTSS symptoms, and that about 40% of person's vulnerability to PTSS is inherited. "A diagnostic tool based on TPH1 and TPH2 could enable military leaders to identify soldiers who are at higher risk of developing PTSS, and reassign their combat duties accordingly," Dr. Goenjian said. "Our findings may also help scientists uncover alternative treatments for the disorder, such as gene therapy or new drugs that regulate the chemicals responsible PTSS." This study appears in the Journal of Affective Disorders. Similar research was done by Dr. Kerry Ressler, an associate professor at Emory University in Atlanta, Georgia. She studied 200 women who witnessed a campus shooting that left five dead and 21 wounded at Northern Illinois University in 2008. Dr. Kessler, whose study appeared in the Archives of General Psychiatry, found that women who had certain genes that made them slower to clear serotonin from their brains were more likely to develop PTSS. In another study, researchers from Mount Sinai School of Medicine found that patients with PTSS had lower levels of serotonin than people without the disorder. These researchers studied military veterans and people with histories of child abuse and domestic violence and then compared them to two control groups: people who had no histories of trauma and people who had such histories but did not develop PTSS. This study also appeared in the Archives of General Psychiatry. Serotonin regulation has already been used as a way to treat depression for many years. Selective serotonin reuptake inhibitors (SSRIs) are antidepressant drugs that prolong the effect of serotonin in the brain by slowing its absorption into brain cells.