[24,25], with which the FA has indeed been found to be associated [2,26,27]. Second, reduced amplitude of the P3 is found in a variety of psychiatric and behavioral disorders, but most notably schizophrenia [28] and alcohol abuse [29]. The reduction in P3 amplitude reflects a genetic predisposition for these disorders rather than a mere functional consequence, because it does not normalize after successful treatment [28] and is also found in unaffected relatives [29]. The latter point is important. To tag a relevant part of the pathway from genetic variation to psychiatric disorder, the endophenotypes must be heritable traits and their heritability must arise partly from the genetic variants that also influence the psychiatric disorder [17].
