The same team of Dutch investigators whose G × E research has focused upon indisputably positive environmental effects also found evidence that the DRD4 7-repeat allele moderated the effect of a maternal psychological condition, unresolved loss or trauma (as measured by means of the Adult Attachment Interview) on early infant development. More specifically, unresolved loss predicted infant attachment disorganization, an early developmental marker of psychological disturbance later in life,45 but only in the case of infants carrying the 7-repeat allele.46 Indeed, these infants manifest both the most and least disorganized attachment behavior when stressed depending on whether their mothers had or had not experienced unresolved loss or trauma in their own lives. Importantly, genotype predicted neither unresolved loss nor disorganization, with the data thus meeting criteria for differential susceptibility (rather than just genetic vulnerability).
