score” might be developed from GWAS or meta-analytic results and tested for its association with externalizing disorders, which would provide even more direct evidence of the validity of the notion that P3AR is an endophenotype for externalizing psychopathology (W. G. Iacono, Carlson, Malone, & McGue, 2002; W. G. Iacono, Malone, & McGue, 2008). Because P3AR is also associated with other disorders, like schizophrenia, the risk score can also be expected to show association with any disorder where this effect is observed.
