Substance use disorders (SUDs) is described as the wild range of the disorder after taking 10 separate classes of drugs (alcohol, caffeine, cannabis, hallucinogens, inhalants, opioids, sedatives, hypnotics and anxiolytics, stimulants, tobacco) (DSM-5). It potentially led to abuser’s mental health disorder, because brain's function in reward, cognitive and stress pathways , as well as personality traits were affected by SUD. More importantly, fathers suffering from SUDs had a great impact on the mental health of their offspring. In addition, the heritability was reported as 54% among drug addicts according to polygenic scores(PGSs) [4, 5]. Therefore, the individual identification and gene polymorphism of SUDs has been the key points in recent years’ studies.
The premise of genetic susceptibility in persons with SUDs has been addressed in some literatures. Molecular genetics, transcription, and gene expression in the brain concerned with SUDs had been put forward by 1998 . The gene transcription and expression variation was related with the amount of heroin use every day  and early age and recurrence. It suggested the probability of hereditary susceptibility of substance use. Moreover, some genetic mutations of identification loci had been found to lead to inherited substance use vulnerability according to the studies of substance abuse father or his offspring.
As a method of genetic research, Short tandem repeat(STR) has variety and wide distribution, low mutation rate, high degree of polymorphism, allele, ability to identify (on each STR loci, several or dozens of allelic fragments), the characteristics of high sensitivity for mutation. Notably, the 19 STR includes 13 CODIS loci (CSF1PO, FGA, TH01, TPOX, VWA, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51 and D21S11) and 6 STR loci in Chinese (D19S433, Penta E, D2S1338, Penta D, D6S1043 and D12S391), which were confirmed by the DNA Analysis Science Working Group (SWGDAM) .
The 19 STR has the higher excluding probability of paternity (probability of exclusion, PE) and probability of discrimination power (DP) in various populations [10, 13–18], as well as the polymorphism test of 19 STR is economical and convenient. Especially, STR is widely used in genetic mapping, species, forensic identification, kinship analysis (especially the paternity test), even disease gene location and polymorphism and genetic disease diagnosis, susceptibility genes exploration, such as the genetic risk of gastric cancer . the Penta D loci might be associated with the aggressive behaviors of schizophrenia, and its Allele 10 and genotypes 10–12 may confer a risk for schizophrenia . However, there were few reports on the application of STR in SUD yet.
Consequently, we come up a hypothesis that the 19 STR loci would not only has personal identification and paternity identification, but also some significant mutation and autosomal gene STR loci polymorphism in addicts. We used blood samples from drug abusers in a certain drug treatment center in China to detect gene polymorphism of the 19 STR loci, and compare it with the reported gene polymorphism in normal Han population. Some individual identification data could be furtherly understood through the characteristics of gene polymorphism in addicts in the current study, on the other hand, the predisposing gene polymorphism of SUD was explored.