The effects of trauma types, cumulative trauma, and PTSD on IQ in two highly traumatized adolescent groups

We investigated the relationship between trauma type, posttraumatic stress disorder (PTSD), and intelligence quotient (IQ) utilizing a development-based taxonomy of trauma in a sample of 390 African-American adolescents and Iraqi refugee adolescents. Utilizing structural equation modeling, we compared different "good-fitting" models that describe the specific relationships between different trauma types, PTSD cluster symptoms (i.e., re-experiencing, arousal, avoidance, and emotional numbness/dissociation), and IQ factors (i.e., perceptual reasoning, verbal comprehension, working memory, and processing speed). Our findings support the hypothesis that different trauma types have different influences, some positive and some negative. Whereas abandonment and personal identity trauma (e.g., sexual abuse) have direct negative effects, secondary trauma (e.g., parents' involvement in war or combat) has a positive effect on IQ. Collective identity trauma (e.g., oppression) did not have either negative or positive effects on IQ. The PTSD components re-experiencing and arousal generally mediated some of the negative effects of traumas on IQ; avoidance and emotional detachment/dissociation generally mediated positive effects. In conclusion, trauma type differentially impacts IQ. However, cumulative trauma dynamics have total negative significant effects on all of the four IQ components: perceptual reasoning, working memory, processing speed, and verbal comprehension.