It is not just in the case of the MAOA gene that the notion of genetic vulnerability takes center stage in research on G × E interactions. Consider the evidence showing that the ‘s' allele of the 5-hydroxytryptamine-linked polymorphic region polymorphism (5-HTTLPR) is associated with increased depression in a high-stress context, with the ‘l' allele functioning protectively.5 Several studies have replicated this finding, providing further support for the conclusion that 5-HTTLPR increases vulnerability to depression in the context of environmental stress.6
