Susceptible Genes, Environment Risk Factors And Their Interactions For Undergraduates With Internalizing Disorders

With the continuous raising of personnel standards requested by knowledge and market economy, and increasing pressures of external environment, undergraduates as a special group show more and more psychological problems. The psychological problems of undergraduates displayed a series of internalizing disorder. Internalizing disorder is a group of psychiatric diseases with anxiety and fear as the major clinical symptoms, including depression, generalized anxiety disorder, obsessive-compulsive disorder, panic disorder, special phobia, social phobia, and agoraphobia. Internalizing disorder as a severe psychiatric problem, which is harm to people's health, should attract researcher's attention. To explore the influence of susceptible genes, environmental factors, gene-gene interaction, and gene-environment interaction to the development of internalizing disorder is the currently urgent problem needed to be figured out.The present study used saliva samples and epidemiological information databases from a comprehensive university undergraduates'mental health survey in Jilin Province at year of 2007, applied the case-control study design to explore internalizing disorder's genetic and environmental factors. Based on variety statistical methods, we analyzed the influence of interactions among BDNF, MAOA and SLC6A4 polymorphisms and environmental factors, and gene-gene on the development of disease. The current results will provide important clues and evidence to the eiology study of internalizing disorder, and are important to efficiently prevent and treat undergraduates with internalizing disorder.Objective,Using the advanced molecular biology techniques, genetic epidemiology, biostatistics, bioinformatics etc and case-control study design to explore the association among BDNF, MAOA and SLC6A4 gene polymorphisms and internalizing disorder; Utilizing multiple Logistic regression to analysis environmental factors associated to university students with internalizing disorder; further analyses on gene-environment and gene-gene interactions with internalizing disorder will provide important clues for the etiology and also theoretical evidence for scientific prevention and treatment of the disease.Methods,①The study subjects were coming from a comprehensive university undergraduates'mental health survey in Jilin Province at year of 2007, using ICD-10 criteria to diagnosis internalizing disorder, which includes depression, generalized anxiety disorder, obsessive-compulsive disorder, panic disorder, special phobia, social phobia and agoraphobia;②In present study both cases and controls came from the field survey. Cases were undergraduates who had been diagnosed as internalizing disorder through the survey and controls were those who are healthy and without any mental illness. We extracted the genomic DNA from the saliva samples and detected the polymorphisms of ten tag SNPs on BDNF, MAOA and SLC6A4 genes using PCR-LDR method. We analyzed the associations among the polymorphisms of ten tag SNPs on BDNF, MAOA and SLC6A4 genes and internalizing disorder. With the consideration of multi-loci association analysis results, the associations among BDNF, MAOA, SLC6A4 and internalizing disorder were further identified;③Multiple Logistic regression was used to explore the environmental risk factors collected during the survey;④The interactions among ten tag SNPs polymorphisms and putative environmental risk factors tested by③step were analyzed by following statistical methods: case-control studies, case only study, based on the results of normal population environmental and genetic independent test case-control study or case-only study will be decided to use, the classical Bayesian approach, the improved methods of Bayesian statistical analysis proposed by Mukherjee and others in 2008;⑤Using the above five statistical analyses to analyze the association among SNP-SNP interactions and internalizing disorder, and using the GMDR analysis to explore the influence of interactions among gene-gene interactions on the incidence of internalizing disorder.Results,①The study recruited 259 cases with internalizing disorder (180 males, 79 females), the youngest one was 18 years and 25 years for the oldest one, the average age was 21.24±1.46 years. A total of 269 controls selected in the survey without any diagnosed psychiatric diseases and they were matching with cases on degree type and grade distribution, including 189 males, 80 females, and the youngest one was 17 years old, the oldest was 26 years, with an average age of 21.40±1.43 years. After tested the two groups on age and gender distribution difference were not statistically significant (Z=-0.959, P=0.337;χ2=0.036, P=0.849);②This study examined rs2030324, rs12273539, rs10835210, rs6354, rs3794808, rs11080122, rs2020942, rs2020939, rs12449783, rs2283724 on BDNF, SLC6A4, and MAOA genes a total of 10 tag SNPs. All tag SNPs did not deviate from the Hardy-Weinberg equilibrium both in case and control groups (P>0.05). The association analyses found that the genotype and allele frequency distributions of loci on SLC6A4 and MAOA had no significant difference between case and control group (P>0.05); the genotype and allele frequency distribution of rs12273539 on BDNF was no significant difference between two groups (P>0.05); the genotype and allele frequency distribution of rs2030324 and rs10835210 on BDNF in case and control group were statistically significant (P<0.05), the mutant allele A carrier on rs10835210 was a risk factor to develop internalizing disorder (OR=1.877, 95%CI 1.385~2.545), the mutant allele C carrier on rs2030324 was a risk factor to develop internalizing disorder (OR=1.347, 95%CI 1.038~1.732). The UNPHASED software was separately conducted to analysis the haplotypes consisted 2~4 loci on SLC6A4 and BDNF. The results showed that none of haplotypes on SLC6A4 was associated with undergraduates'internalizing disorder (P>0.05); all the haplotypes on BDNF were associated with undergraduates'internalizing disorder (P<0.001);③Based on clinical sub-group analyses found that rs10835210 on BDNF gene was associated with anxiety, fear of internalizing disorder, obsessive-compulsive disorder (P<0.05). rs12449783 on SLC6A4 was associated with anxiety of internalizing disorder(P<0.05). rs2020942 on SLC6A4 was associated with anxiety, fear of internalizing disorder, and obsessive-compulsive disorder(P<0.05). rs2283724 on MAOA gene was associated with fear of internalizing disorder(P<0.05). In addition to the above sites, other sites with no statistical correlation among the clinical sub-groups(P>0.05);④According to the multiple Logistic regression analysis showed that better father mood, better mother mood, easy pouring out, not being a single child in family, having a good relationship with mother, and less restriction from father were the protective factors of the development of internalizing disorder;⑤No statistically significant interactions were found in the gene-environment interaction analysis;⑥The gene-gene interaction was found that no interactions of two loci located on the different gene was associated with internalizing disorder. The GMDR analysis identified that the model consisted of rs10835210/rs2030324 loci on BDNF gene was the best model to present the multi-loci interaction analysis. Person who carries CA or AA genotypes on rs10835210 and CT or CC genotypes on rs2030324 of BDNF gene at the same time will have more risk to affect the disease. The risks were 1.761 and 3.353 times respectively compared to the person who carries CC genotype on rs10835210 and TT genotype on rs2030324 of BDNF gene.Conclusion,①The worse father and mother mood, less pouring out, being a single child in family, having a terrible relationship with mother, and more restriction from father were the risk factors of the development of internalizing disorder;②BDNF gene may be the susceptible gene of internalizing disorder; SLC6A4 and MAOA genes may not be the susceptible gene of internalizing disorder, but still may have other minor functions of causing disease;③No statistically significant interactions were found in the gene-environment interaction analyses;④The gene-gene interactions were found that the model consisted of rs10835210/rs2030324 loci on BDNF gene was associated with the disease. Carriers with mutational alleles on rs10835210 and rs2030324 of BDNF gene at same time will increase the risk of developing the disease.The present stuay was based on the issue of psychiatric comorbidity, put the theory of structural equation model and molecular biological lab work together, firstly explored the etiology of internalizing disorder, used a variety of statistical methods to analysis gene-gene, gene-environmental interactions, and added more accuracy to detect the risk of environmental and genetic factors to internalizing disorder. The present results hint that the internalizing disorder as a group of commorbidity having the same or similar causation, and heredity and environment do contribute to the incidence of the disease. Our findings will promot to clarify the cause mechanism of the disease, provide the fundermantal basis for setting up the target treatment method and efficient method of preventing disease, and offer the important clues for complex disease research.