Participants were from a NICHD funded longitudinal study of child maltreatment in urban young adolescents. The ethnically diverse sample (Caucasian, African American & Hispanic) consisted of 303 maltreated and 150 comparison children ages 9 to 12 at their inclusion in the study. The maltreated children were recruited from active cases in the Los Angeles County Department of Children and Family Services and the demographically similar comparison sample was recruited from the same zip-codes as the maltreated sample. The subjects were evaluated three times with 1-1.5 year interval. The Memory for Names subscale of the Woodcock-Johnson Test of Cognitive Ability-Revised (WJ-R; Woodcock & Johnson, 1989) was used.
Latent growth curve analysis (LGC) based on structural equation modeling was performed. The LGC model used age as the axis of change because cognitive ability was expected to change systematically with age. The single group LGC model showed significant pattern of change in long-term memory functioning over time. Multi-group analysis of the LGC indicated significant differences in long-term memory development between the maltreatment and the comparison groups. The average baseline score of long-term memory at age 9 for the maltreatment group (492.5) was lower than the comparison group (495.2). Average rate of growth in long-term memory per year was 2.5 for the maltreated group and 3.2 for the comparison group, indicating a lower growth rate in the maltreated group than the comparison group. Significant sex difference was only found in the maltreatment group (b=1.1, p<.01). The maltreated girls exhibited significantly lower growth rate in memory functioning than the maltreated boys.
This study serves as an important step in beginning to understand the developmental trajectories of long-term memory in maltreated children. The deficit in cognitive ability may negatively influence academic achievement of children, which in turn may increases risk for school drop-out and unemployment. Given the lower growth rate in long-term memory for maltreated children, the gaps between maltreated and nonmaltreated children tend to become larger with age. Therefore, this finding addresses the potential value of early intervention. Sex differences in the development of memory have clear implications for understanding clinical disorders related to memory and traumatic experiences, most notably posttraumatic stress disorder. It is well known that PTSD incidence is approximately twice as high in women compared to men.