Children who are more intelligent at age 6 may be less likely to experience trauma by age 17 and if they do, may be less likely to develop post-traumatic stress disorder (PTSD), according to a report in the November issue of Archives of General Psychiatry, one of the JAMA/Archives journals. In contrast, children who have anxiety disorders and conduct problems at age 6 appear more likely to develop PTSD following exposure to traumatic events.

PTSD is a psychological condition that occurs following exposure to a traumatic event, such as warfare, crime, a natural disaster or a life-threatening illness. Symptoms include sleep problems, depression, flashbacks and anxiety. However, not every individual exposed to such an event will develop PTSD, according to background information in the article. Researchers currently believe that certain factors--such as gender, race and socioeconomic background--predispose individuals to experiencing trauma and also increase their risk of developing PTSD following exposure to trauma. These factors may be more important than the type or severity of the trauma experienced in determining who will develop PTSD.

Naomi Breslau, Ph.D., and colleagues at Michigan State University, East Lansing, studied 713 children (336 boys and 377 girls) born between 1983 and 1985 at two Michigan hospitals, one located in a disadvantaged urban community and one in a middle-class suburban community. At age 6, the children were given intelligence tests. Their teachers rated their behavior at school, and parents reported any symptoms of anxiety disorders, which include phobias (irrational fears), separation anxiety and generalized anxiety disorder. At age 17, the participants completed an interview designed to measure the number and type of traumatic events they had experienced in their lives and also how deeply those events affected them, including whether they had ever experienced symptoms of PTSD.

By age 17, 541 (75.9 percent) of the participants had experienced a traumatic event and 45 (6.3 percent, 8.3 percent of those experiencing trauma) met criteria for PTSD. Those who had an IQ of greater than 115 at age 6 were less likely to be exposed to any type of trauma, especially violent assaults, and were less likely to develop PTSD by age 17 when they did experience a traumatic event. Those whose teachers reported that they had more conduct problems than normal at age 6 had a higher risk of being exposed to violent crime, such as rape, mugging or beating, by age 17. Those children, and also those with anxiety disorders at age 6, were about twice as likely as those who did not have conduct problems or anxiety disorders to develop PTSD by age 17 if they were exposed to a traumatic event.

Sociodemographic factors also influenced the children's risk for exposure to traumatic events and for PTSD. "We observed in these data the sex-related pattern reported in previous studies, with males more likely to be exposed to trauma, and females more likely to experience PTSD following exposure," the authors write. "As in previous studies, the cumulative incidence of exposure to traumatic events was higher in inner-city (urban) youth than in suburban youth."

Individuals with high IQ were less prone to PTSD even if they had other factors, such as anxiety disorders and an urban background, stacked against them. "The ways in which high IQ might protect from the PTSD effects of traumatic exposure are unclear," the authors conclude. "The findings underscore the importance of investigating cognitive processes in a person's responses to challenging and potentially traumatic experiences and the involvement of general intelligence in shaping them."