It should be mentioned that not all subjects were followed an equal number of years and not all were followed across the age range studied (8–29). Subjects entered the study at different ages and had their last ERP assessment at differing ages. Although these limitations are present, the overall conclusion that P300 trajectories are related to risk status and male gender in early development appears to be solid. The analyses support previous findings for the effects of the CHRM2 gene and P300 amplitude. Because previous reports find a relationship between CHRM2 and alcohol dependence, it was somewhat surprising that the CHRM2 variation was not associated with familial risk. However, the absence of risk status association with the CHRM2 gene may indicate that CHRM2 variation is only manifest when those with high risk status actually become alcohol dependent. Nevertheless, the present results suggest that both high risk status and CHRM2 variation are associated with a low amplitude trajectory in early development that from other investigations (Hill et al., 2009) appears to be related to SUD outcome.
