Similar to opioid receptor genes, the BDNF gene also contains several SNPs that have been linked to nicotine or alcohol abuse [86]. Itoh et al. [88] conducted a study to determine the personality traits associated with the G196A SNP (rs6265) of the BDNF gene. The Temperament and Character Inventory personality test was administered to a Japanese sample of 95 females and 56 males, and the results revealed significant differences among the personality traits of the three genotype groups in females (df=2.93, f=5.33, P=0.006) [88]. Females homozygous for valine (Val) scored significantly higher in reward dependence (P=0.013) and extraversion (P=0.022), both of which are negatively correlated with depression [88]. The findings suggest that female carriers of the methionine (Met) allele may be more likely to develop mood disorders such as depression [88].
