We have examined both of the SLC6A4 polymorphisms mentioned above to determine whether they influence acute responses to amphetamine using our sample of healthy volunteers described in the previous section (Lott et al. 2006). When these two polymorphisms were analyzed separately, individuals homozygous for the 10-repeat allele of the Intron 2 VNTR showed a stronger euphoric response. When the polymorphisms were analyzed jointly, no significant association was observed, but trends in the predicted directions were observed—subjects homozygous for the low expressing alleles (S and 10-repeat) had the strongest responses to amphetamine (for the POMS Anxiety, DEQ Feel Drug, and ARCI Euphoria scales). These data identify a non-significant trend towards decreased expression of the serotonin transporter being associated with increased responses to stimulants.
