Intelligence and other predisposing factors in exposure to trauma and posttraumatic stress disorder: a follow-up study at age 17 years

CONTEXT: Prospective data on standardized measures of early predispositions would allow a strong test of hypotheses about suspected risk factors of posttraumatic stress disorder (PTSD) and exposure to traumatic events. OBJECTIVE: To prospectively examine the extent to which intelligence, anxiety disorders, and conduct problems in childhood influence the risk for PTSD and for exposure to traumatic events. DESIGN: A longitudinal study of a randomly selected sample assessed at age 6 years and followed up to age 17 years. SETTING: Samples were randomly selected from the 1983-1985 newborn discharge lists of 2 major hospitals in southeast Michigan (N=823). PARTICIPANTS: Cohort members with follow-up data at age 17 years (n=713; 86.6% of the initial sample). MAIN OUTCOME MEASURES: Cumulative exposure up to age 17 years of qualifying traumatic events; DSM-IV PTSD among participants who have experienced 1 or more traumatic events. RESULTS: Youth with teacher ratings of externalizing problems above the normal range at age 6 years were at increased risk for exposure to assaultive violence (adjusted odds ratio, 2.6; 95% confidence interval, 1.4-4.9). Youth aged 6 years with an IQ greater than 115 had decreased risk for exposure to traumatic events (adjusted odds ratio for assaultive violence, 0.3; 95% confidence interval, 0.2-0.7); a decreased risk for nonassaultive trauma (adjusted odds ratio, 0.6; 95% confidence interval, 0.3-0.9); and a decreased conditional risk for PTSD (adjusted odds ratio, 0.2; 95% confidence interval, 0.1-0.9). The conditional risk for PTSD was increased for youth with anxiety disorders and teacher ratings of externalizing problems above the normal range at 6 years of age. CONCLUSIONS: The results of this prospective community study highlight the role of intelligence in avoidance of exposure to traumatic experiences and their PTSD effects. They underscore the need for investigating cognitive processes in persons' responses to traumatic experiences and the involvement of general intelligence in these processes.