Intelligence and Other Predisposing Factors in Exposure to Trauma and Posttraumatic Stress Disorder: A Follow-up Study at Age 17 Years
Breslau N, Lucia VC, Alvarado GF;
Commented by , 24 Nov 2006
Background
There is evidence that personal predispositions might influence the risk to exposure to traumatic events and to PTSD.
Aims of the study
To examine the extent to which intelligence, anxiety disorders, and conduct problems in childhood influence the risk for PTSD and exposure to traumatic events.
Method
A longitudinal study of a randomly selected sample assessed at age 6 years and followed up to age 17 years. Intelligence as well as the presence of anxiety disorders and conduct disorders were assessed at age 6. Follow-up data at age 17 years were obtained for 86.6% of the initial sample. Main outcome measures included cumulative exposure up to age 17 years of qualifying traumatic events and PTSD among participants who have experienced 1 or more traumatic events.
Results
The main results of the study include:
- youth with a high level of conduct disorders at age 6 years were at increased risk for exposure to assaultive violence
- youth aged 6 years with an IQ greater than 115 had a decreased risk for exposure to traumatic events and a decreased risk for PTSD after exposure to trauma
- the risk for PTSD after exposure to traumatic events was increased for youth with a high level of anxiety disorders and a high level of conduct disorders at 6 years of age.
Professor Pull's comments
According to DSM-IV-TR, the essential feature of PTSD is the development of characteristic symptoms following exposure to an extreme traumatic stressor.
Current conceptions of PTSD emphasize the role of preexisting vulnerabilities in the etiology of the disorder, in addition to trauma characteristics such as trauma magnitude. Among the factors that have been associated with an increased risk for exposure to trauma as well as for developing PTSD after a traumatic event are: intelligence, early psychiatric disorders such as preexisting anxiety and depressive disorders, and childhood conduct disorders.
The extent to which personal predispositions place individuals at risk for exposure to trauma and increase their risk for the PTSD effects of exposure remains unclear however, owing to inconsistencies across studies and the retrospective nature of nearly all the available data.
The strengths of the study by Breslau et al are
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that it is a prospective study and
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that all key variables were assessed in a systematic way using standardised and validated instruments.
Data on childhood factors (intelligence, anxiety disorders and conduct disorders) were gathered at age 6 years. Data on exposure to traumatic events and PTSD were gathered at age 17 years and cover the participant’s cumulative experience up to the time of the interview.
The Wechsler Intelligence Scale for Children–Revised was used to measure IQ at age 6 years. Behavior problems at age 6 years were rated by teachers, using the Teacher Report Form. The DSM-III-R anxiety disorders (simple phobia, separation anxiety, overanxious disorder, and generalized anxiety disorder) were measured by the National Institute of Mental Health Diagnostic Interview Schedule for Children–Parent version 2.1 in interviews with mothers.
The results of the study emphasize the role of intelligence, childhood anxiety disorders and early conduct disorders in the exposure to trauma and the occurrence of PTSD. They highlight, in particular, the role of intelligence in avoidance of exposure to traumatic experiences and their PTSD effects and "underscore the need for investigating cognitive processes in persons' responses to traumatic experiences and the involvement of general intelligence in these processes".