Twin-based study of the complex interplay between childhood maltreatment, socioeconomic status and adult memory.

Childhood maltreatment and low socioeconomic status (SES) are considered stressful environmental events with lasting detrimental effects on adult mental health and associated cognitive performance, such as memory. However, the association between childhood maltreatment and low SES remains unclear, probably due to design limitations and putative confounding factors. Particular concerns have been raised on genetic influences, as genetic background may modulate the effects of environmental stressors. The aim of the present study was to examine the effect of childhood maltreatment on adult memory in low- and high-SES subjects, free of confounding due to other environmental and genetic influences. A monozygotic twin design based on 188 healthy adult subjects (94 twin pairs) from the general population was conducted. This design based on genetically identical individuals allowed disentangling the unique environmental effects of childhood maltreatment on memory, which was explored in low and high SES. Results showed that the unique environmental effects of childhood maltreatment were only evident in the high-SES group (β = -0.22; SE = 0.08; p < 0.01; 95 % CI = -0.375 to -0.066). By contrast, no evidence for this effect could be detected in the more stressful low-SES group. These results suggest that enriched environments may provide a more stable context where early stressful experiences can influence cognitive processes. This study provides preliminary support for the inclusion of environmental enrichment in studies addressing the impact of childhood maltreatment on adult cognition and psychiatric disorders.