Children who are more intelligent at age 6 years may be less likely to experience trauma by age 17 years and to develop post-traumatic stress disorder if they do experience a triggering-type event, according to an article in the November issue of the Archives of General Psychiatry.

In contrast, children who have anxiety disorders and conduct problems at age 6 years appear more likely to develop the disorder following exposure to traumatic events.

In the current study, Naomi Breslau, PhD, and colleagues at Michigan State University, East Lansing, studied 713 children (336 boys, 377 girls) born between 1983 and 1985 at two nearby hospitals, one located in a disadvantaged urban community and one in a middle-class suburban community.

At age 6 years, the children were given intelligence tests. Teachers rated behavior at school and parents reported any symptoms of anxiety disorders, which included phobias, separation anxiety and generalized anxiety disorder. At 17 years, participants completed an interview designed to measure the number and type of traumatic events they had experienced in their lives and how deeply those events affected them, including whether they had ever experienced symptoms of the disorder.

At 17 years, 541 (75.9 percent) of participants had experienced a traumatic event and 45 (6.3 percent, 8.3 percent of those experiencing trauma) met criteria for post-traumatic stress disorder. Adolescents who had an intelligence quotient 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 the disorder by age 17 when they did experience a traumatic event.

Participants 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, at 17 years. 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 the disorder by age 17 if exposed to a traumatic event.

Sociodemographic factors also influenced the children’s risk for exposure to traumatic events and for development of the disorder. “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 post-traumatic stress disorder following exposure,” the authors wrote. “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 intelligence were less prone to develop the disorder even if they had other factors, such as anxiety disorders and an urban background, stacked against them. “The ways in which high intelligence might protect from the PTSD effects of traumatic exposure are unclear,” the authors concluded. “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.”