National Twin Registry, a valuable data bank

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Having a twin sister is a slightly stronger family bond, for the same reason that we were born and do everything together,” said Camila Mondragón, a high school student.

Her identical twin sister is called Valeria, they both come from a family of artists and that is why they share a taste for drawing; but only that, because, in reality, they claim to be very different from each other: Camila likes to wear dresses and Valeria pants and shirts; one loves sports and the other doesn’t.

“We understand each other well because most of the time we are together, it is inevitable that we do not know almost everything about the other. We are used to the fact that if I need advice from her, I ask her and vice versa, or even I can tell what Camila is feeling just by seeing her face, ”said Valeria Mondragón, a high school student.

The mother of identical twins has always been interested in family welfare, which is why she found the Mexican Registry of Twins or TwinsMx, which is a UNAM project to record and collect information from people who participated in multiple births (twins, fraternal twins, , triplets) to analyze characteristics of the Mexican population in general and the incidence of various diseases, studying them as a genetic and environmental model.

Four researchers participate in this project: Alejandra Medina Rivera, from the International Laboratory for Research on the Human Genome at UNAM, who is in charge of analyzing the DNA samples; Alejandra Ruiz Contreras, from the Faculty of Psychology at UNAM, who participates in the evaluation of mental and cognitive health; Sarael Alcauter Solórzano, from the UNAM Neurobiology Institute (Juriquilla campus, Querétaro), who is in charge of studying the magnetic resonance images, and Miguel Rentería, from the Queensland Medical Research Institute, Australia, and who contributes part of the design of the study.

“This type of twin registries have been carried out in Europe, North America and Australia, because they allow us to identify how much weight genetic and environmental factors have on physical and mental health issues in the population. In Mexico, we began to implement it in 2019 and, despite the pandemic, until July 2022, more than 3,200 twins, twins, and triplets have participated,” said Sarael Alcauter Solórzano.

He explained that the data obtained has been valuable, because identical twins have around one hundred percent of their genetic material the same; while twins or buddies have about 50 percent similarity, so this allows mathematical models to establish the weight that both genetics and the environment have in a particular phenotype or health issue.

For example, he pointed out, when evaluating mental health issues, basically any phenotype such as depression or anxiety, with various data from identical twins and fraternal twins, it is possible to know which has more weight, genetics or the environment. This is important for public health decisions and potentially for genetic treatments that may be developed.

“Another example would be size or stature. If we take the height of thousands of identical twins and if it is more similar between them than between the fraternal twins, it is because there is a genetic component. But if the height was similar between the fraternal twins more than in identical twins, then we would talk about the environmental part, ”he asserted.

In this way, university students obtain information on the prevalence and characteristics of different diseases in the Mexican population, such as overweight, diabetes, hypertension or Parkinson’s disease, considering that there is a particular genetic mix in the country.

“Most of the knowledge comes from studying populations of European, American or Canadian origin, which indicate that anxiety, for example, has a 14 percent inheritance. But this result does not mean that it is equitable for all populations, that is, they are made in other nations and do not reflect what happens in our mestizo population in Mexico,” the academic explained.

Information from people who participated in multiple births (twins, twins, triplets) is handled to analyze characteristics of Mexicans in general; You can register on the following website:

The study

The data collection of twin brothers is done through the following website:, which is the Mexican Registry of Twins. Upon entering, you must go to the “Register” section, where participants can share their information (it is kept anonymously) through a series of questionnaires on aspects of physical and mental health, as well as recreation.

“Some of the participants, apart from helping us with their information, go to the Institute of Neurobiology of the National University, in Querétaro, with the purpose of giving them a free magnetic resonance imaging session, with which we can characterize the way and how their brain works. ; a DNA sample collection, as well as interactive cognitive tests. If there is any interest in attending these studies, we ask that you first contact us for a brief interview”, highlighted Alcauter Solórzano.

“I think it’s worth coming to the UNAM Juriquilla campus, helping science and at the same time getting to know yourself a little better together with your twin sister or brother,” Camila Mondragón mentioned.

TwinsMx specialists commented that one of the first results in this study has been related to visual health. They analyzed a database of the order of 2,800 twins who reported the use of glasses, astigmatism and myopia were evaluated in them and it was concluded that these two conditions have an inheritance of between 62 and 66 percent, that is, here genetics has greater weight than the environment.

In other preliminary results, depression, hostility, phobic anxiety and hypochondriasis were found to be more similar between identical twins than between fraternal twins. For example, if one person has high levels of depression, there is a good chance that their identical twin will also have high levels.

However, in terms of magnetic resonance imaging, there is hardly any information on about 200 twins, so the university researchers are calling for more people to participate in the study carried out at the Institute of Neurobiology, in Querétaro.

The National Registry of Twins will be a valuable data bank for the Mexican and international scientific communities, because it can be used only for questions related to research, with the aim of generating knowledge that can be useful for the population.

Photo: Mexican Registry of Twins.

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