The National Twin Registry, a valuable data bank

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

Her identical twin sister is called Valeria, both come from a family of artists and therefore 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 likes sports and the other doesn’t.

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

The mother of identical twins has always been interested in the well-being of the family, which is why she founded the Mexican Registry of Twins or TwinsMx, which is a UNAM project to record and collect data from people who have participated in multiple births (twins, fraternal twins, , triplets) for analysis of the characteristics of the Mexican population in general and the frequency of various diseases, studying them as a genetic and ecological model.

Four researchers participate in this project: Alejandra Medina Rivera, from the International Laboratory for Human Genome Research at UNAM, who is in charge of analyzing 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 Institute of Neurobiology of UNAM (Juriquilla campus, Querétaro), who is in charge of the study of the magnetic resonance images, and Miguel Rentería, from the Queensland Institute of Medical Research, Australia, and who partly contributed to the design of the study.

“This type of twin registry has been carried out in Europe, North America and Australia, because it allows us to determine how much weight genetic and environmental factors have on the physical and mental health problems of the population. In Mexico, we started implementing it in 2019 and, despite the pandemic, by July 2022, more than 3,200 twins, triplets and triplets have participated,” said Sarael Alcauter Solórzano.

He explained that the data obtained was valuable because identical twins have about one hundred percent of their genetic material the same; while twins or friends have about 50 percent similarity, so this allows mathematical models to determine the weight that both genetics and environment play in a particular phenotype or health problem.

For example, he pointed out, when assessing mental health problems, basically any phenotype like depression or anxiety, with different data from identical and fraternal twins, it is possible to know which has more weight, genetics or 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 among them than among fraternal twins, it is because there is a genetic component. But if the height was more similar in twins than in identical twins, then we would be talking about the ecological part,” he said.

In this way, students get information about the prevalence and characteristics of various diseases in the Mexican population, such as overweight, diabetes, hypertension or Parkinson’s disease, given that the country has a special genetic mix.

“Most knowledge comes from studies of populations of European, American or Canadian descent, which show that anxiety, for example, has 14 percent heritability. But this result does not mean that it is the same for all populations, that is, that they were made in other nations and do not reflect what is happening in our mestizo population in Mexico,” the academic explained.

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


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

“Some of the participants, in addition to helping us with their information, go to the Institute of Neurobiology of the National University of Querétaro, with the aim of providing them with a free magnetic resonance imaging, with which we can characterize the way and how their brain works. ; collection of DNA samples, as well as interactive cognitive tests. If there is an interest in attending these studies, please contact us first for a short conversation”, said 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 noted.

TwinsMx experts commented that one of the first results in this study was related to vision health. They analyzed a database of 2,800 twins who reported using glasses, assessed astigmatism and myopia, and concluded that these two conditions are inherited between 62 and 66 percent, i.e. that genetics has more weight here than the environment.

Other preliminary results showed that depression, hostility, phobic anxiety, and hypochondria were 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, as far as magnetic resonance imaging is concerned, there is hardly any data on about 200 twins, so university researchers are calling for more people to participate in the study, which is being carried out at the Institute of Neurobiology in Querétaro.

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

Photo: Mexican Twin Registry.

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