1、ObjectiveTo reveal abnormalities of decision-making processing mechanism in patients with depression,to investigate the effect of5-HTTLPR polymorphismin to choice ability of patients with depression;to provide theoretical and practical basis for depression pathogenesis and etiology study.It is a better way to explain individual differences about prognosis of patients with depression and to provide value for clinical diagnosis, efficacy assessment.2、Method1)To measure5-HTTLPR genotypes and alleles of100patients with mild or moderate depression from Han Chinese,and100normal controls by PCR amplification.The depression patients were grouped by genotype and gene frequencies.2)All subjects were examined by three different kinds of decision tasks (risk-. ambiguity and certain)programmed with E-prime, and recorded reaction time、correct rates and risk appetites.3、Result1) There were significant differences statistically in5-HTTLPR genotype frequency (x2=7.22, P=0.027),and the differences were not statistically significant in allele frequency(x2=3.48, P=0.061).However,S allele frequency in case group was higher than the control (61.3%:56%), L allele frequency was lower than the control group (35.5%:42%).2) There were significant differences statistically in reaction time (p<0.05) and no significant differences in correct rates (p>o.o5) between depression group and controls group under the same type of uncertainty choice.There were no significant differences statistically in reaction time and correct rates under certainty choice (p>o.o5) 3)①Compared the reaction time among three genotype of depression group under riskandambiguitychoice:[risk:SS(2006.18±101.23),SL(1998.17±98.72),LL(1543.21±78.36);a mbiguity:SS(2136.18±121.79),SL(2011.13±109.27),LL(1679.18±89.15)].The mean reaction time of SS and SL group was longer than LL group (p<0.05) and the differences were signigant (p<0.05).There were no significant differences statistically in reaction time,but SS group was longer slightly than SL group(p>o.o5)②Compared the correct rates among three genotype of depression group under risk and ambiguitychoice:[risk:SS(49.77±3.70),SL(50.10±3.72),LL(52.40±3.58);ambiguity:SS (48.65±2.68),SL (49.88±3.89),LL(53.64±3.79)],the differences among three groups were no significant statistically (p>o.o5),and the mean of SS and SL groups was lower than LL group,and SS group was lower slightly than SL group.③There were no significant differences statistically in reaction time and correct rates under certain choice (p>o.o5)4、Conclusion1)SS type of5-HTTLPR had more Possibility as depression patients,S allele might be a susceptibility gene.2)The choice processing of depression patients might be affected by their conditions.3)There were some differences in choice processing among different genotypes of5-HTTLPR, SS genotype might influence choice process.