 Therefore, part of the association between parental marital status and ADHD diagnosis among children in this sample is due to the confounding variable of maternal DRD2 genotype.Both of these studies also found evidence for gene–environment interaction.A polygenic score (PGS; also called a polygenic risk score), which is a number assigned to individuals based on variation in multiple genetic loci and their associated regression weights from genome-wide association studies, can also be used to demonstrate gene–environment correlation.