The Construction and Prospects of the Chongqing Twin Children Database Yixiao Fu,1 Peng Xie,3 Huaqing Meng,1 Qing Qin,1 Lu Jia,1 Qi Li,3 Yi Huang,2 Xiao Hou,5 Qinghua Luo,1 Xiaohong Ma,2 Wei Deng,3 Yingcheng Wang,3 Hua Hu,1 Lian Du,1 Kun Feng,1 Haitang Qiu,1 Yun Xiang,4 and Tao Li6 1 Department of Psychiatry, The First Affiliated Hospital, Chongqing Medical University, Chongqing, China 2 Department of Psychiatry, West China Hospital, Sichuan University, Chengdu, China 3 Department of neurology The First Affiliated Hospital, Chongqing Medical University, Chongqing, China 4 The Forth Hospital of Chengdu, Chengdu, China 5 Chongqing Medicine College, Chongqing, China 6 King’s College London, Department of Psychological Medicine, Institute of Psychiatry, London, United Kingdom wins could play a crucial role in our understanding the proportion of children under the age of 16 in the Tof genetic contributions to numerous etiologically total population of developing countries is higher than complex disorders. In China, although adult twins are that of developed countries, the total number of relatively rare, twins will become increasingly avail- affected children is much higher. Currently, the inci- able due to increasing twin birth rates. Thus, child dence of child mental health problems is approximately twin data will be a valuable resource to contribute to 15% in China (Junmian, 2000; Xueyong, 2002), the field of child and adolescent psychopathology. meaning that 50 million children and teenagers may The first twin database of children aged from 6 to 16 need mental health services. was established in Chongqing, R.P., China. In this The key to the solution of these mental health article, we will discuss our experiences in establish- ing the twin database, completed in three steps — issues lies in the studies of the effects of heredity and the first step being to search and identify twins, the environment on the psychological development and second being to keep contact with the twins and the mental health of children. Thus, we aim to set up a final being to seek cooperation with the twin fami- twin database to aid researchers in their work on lies, and its future prospects. Our twin database has mental health problems in Chongqing, China. proven to be an efficient method for the investiga- The period of 6 to 16 years of age is a critical stage tion and data collection of twin children in China. The for individual psychological development, during results of our present study suggest that the inclu- which children will witness a dramatic development in sion of twin information in the residence registration their memory, thinking, self-concept, and interper- of the public security bureaus in the future may sonal skills. However, children at this period were also ensure a smooth run of research based on the at high risk of suffering from mental disorders. demographic resources. We propose that school net- Therefore, our children twin database investigation works may be adopted as the preferred method of mainly focused on children aged 6 to 16 years old. collection of twin records for future studies. Keywords: twin database, children, mental health, environ - Twin Method, Twin Databases SQ and ment, heredity Chongqing Children Twins Project It is well known that most twins share a high degree of similarity in their genetic makeup. Monozygotic twins Background to the Establishment (MZ) develop from the same fertilized ovum and have of the Twin Children Database complete inheritance foundation, while dizygotic twins In this era of rapid social and technological advance- (DZ) develop from different ova and share only half of ments leading to life complexity, a majority of diseases the genetic makeup. By comparing monozygotic twins seriously endangering children’s physiological func- and dizygotic twins, we can examine the interplay tions have been effectively controlled in most parts of between heredity and environment. Thus, twin data is the world. However, the growing incidence of psycho- logical problems has aroused widespread concern in international communities. Received 21 April, 2008; accepted 27 August, 2008. The incidence of mental health problems of children Address for correspondence: Dr Huaqing Meng, Institute: Department in developed countries lies within the range of 10% to of Psychiatry, The First Affiliated Hospital, Chongqing Medical 20%, and in developing countries may be even higher University, No.1, Yixueyuan Road, Chongqing, 400016 China. (Hackett & Hackett, 1999). It is noteworthy that since E-mail: [email protected] Twin Research and Human Genetics Volume 11 Number 6 pp. 629–633 629 Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.76, on 28 Sep 2021 at 14:33:00, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1375/twin.11.6.629 Yixiao Fu et al. an ideal model for the study of the effects of hereditary provide a great convenience for scientific researches. and environmental factors on human characteristics. The influences of heredity and environment on the Initial Construction of the Twin Database human body, mental health, temperament and person- in the Chongqing Municipality ality have always been a focus of intensive debate. The initial construction of the twin database for chil- Twin analysis provides an important method to dren aged 6 to 16 years in the Chongqing municipality analyze and study this issue. Current available twin includes three steps: databases are almost exclusively based in western countries, such as the Norwegian Twin Registry 1. to search and identify twins (as there is no current (Bergem, 2002), the Danish Twin Registry (Skytthe et twin registration system or ready-made twin infor- al., 2002), the Swedish Twin Registry (Pedersen et al., mation in population databases of Chongqing 2002), the Netherlands Twin Registry (Boomsma et al., 2. to maintain contact with the twins 2002), Minnesota (Iacono & McGue, 2002) and 3. to seek cooperation with the twin families. Wisconsin (Van Hulle et al., 2002) Twin Twin Registry,Virginia and North Carolina Twin Registries In the initial stage, we aimed to find the most efficient and Mid-Atlantic Twin Registry, Sri Lankan Twin way to recruit twins with good reliability at a low cost Registry (Sumathipala et al., 2002). Several attempts in order to facilitate the further expansion of the twin have also been made in China to establish twin data- database and the relevant in-depth studies and also to bases; for example, in 2002, Huiying Yang established offer suggestions for the establishment of self-con- a database of 8583 pairs of twins (Yang, 2002). In tained twin children databases. order to investigate eye diseases, another twin database including 9000 pairs of twins was established in Searching and Identifying Twin Resources Guangzhou (He et al., 2006). However, twin databases The following three methods were employed to search in China are still lacking. twins aged between 6 and 16: Therefore, we sought to establish a twin database 1. Residence registration management in the public for children aged between 6 and 16 years old, with a security bureaus: The records (including date of special emphasis on mental development (including birth, sex, home address, and so on) of children cognitive functions and personality traits) and mental aged between 6 and 16 in Chongqing municipality health in the Chongqing municipality. Based on this were obtained through the residence registration twin database registry, we aim to perform a compre- management system of the public security bureaus. hensive, long-term longitudinal study on the effects of Candidate twins or multiples were determined by heredity and environment on the human body, tem- their identical or similar date of birth, home perament and personality traits. address and surnames (the twins subjectively desig- nated by this method may return some false City Profile of Chongqing positives and sometimes it is difficult to keep Chongqing is the largest and most populated city in contact with those twins whose home address regis- the world, with an estimated population of 32 million tered at birth was changed. Therefore, only records people. The city is located in the center of Western from the Yuzhong District were collected). China and covers an area of 82,403 square kilometers. 2. Education commission and school networks: It is also the economic, educational and political center Considering the fact that the subjects in this study of Western China. are children aged between 6 and 16 and are at The geographical features of Chongqing are char- school age, we set up to enroll twins from primary acterized by its rivers and hills, an extensive chain of and middle schools. Institutional approval from rolling mountains and its crisscrossing river network. local education commissions was obtained. We col- The geographical environments, together with the lected twin records from school archives of seven social and economical displacements have contributed main urban districts in Chongqing municipality — to the unique child psychological characteristics in Chongqing. Yuzhong District, Shapingba District, Jiangbei According to statistics, the number of permanent District, Nan’an District, Dadukou District, residents in Chongqing municipality is 27,709,800, of Jiulongpo District and Beipei District. which 6- to 16-year-old children account for 21.2% 3. Twin reunions held by public media: Our research and the twin birth rate is 1.8%. Note that resident pop- team initiated cooperation with newspapers and ulation herein refers to those who have resided in the magazines, covering nine main urban districts in townships, towns, or street communities for more than Chongqing municipality — Yuzhong District, 6 months or those who have resided in them for less Shapingba District, Dadukou District, Nan’an than 6 months but have been away from the place of District, Jiangbei District, Jiulongpo District, Beipei their permanent household registration for more than 6 District, Yubei District and Ba’nan District — to months and their new household registration has not hold twin reunions and attract the active participa- yet been settled.