Italian Twin Registry

Project Title: Italian Twin Registry

Duration of the project: The Italian Twin Registry (ITR) was established in 2001, when a broad project of the Italian Ministry of Health supported its implementation at the Istituto Superiore di Sanità. The ITR activity is still ongoing.


Main Topic

The Italian twin registry is an extremely powerful tool for understanding how genes and environment affect human health, including psychological well-being. At the time of enrolment, adult twins (aged 18 years and over) give their written consent to be contacted for future research projects proposed by the ITR. Parents of underage twins sign an informed consent form to allow their children to participate.
To date, approximately 29.000 twins have joined the ITR. The enrolment of new pairs continues all over the country and involves all age groups.
Identical (monozygotic) and fraternal (dizygotic) twins are enrolled in the registry and, at first contact, socio-demographic and anthropometric characteristics are collected. Moreover, across different studies, the ITR collects information on a large spectrum of phenotypes by either self-reported questionnaires or clinical examinations. The questionnaires are sent by mail, given by hand to the twins if a face to-face meeting is included in a specific study or directly fill in by twins using a web-based platform. Biological samples and clinical information (such as blood pressure, history of diseases, carotid ultrasound, sleep disorders, Neuroimaging) are also collected according to the aims of the studies.
Moreover, by geocoding each participant’s place of residence, the twin database can be further enriched with information on the level of socio-economic deprivation and environmental exposure (eg: pollutants or green areas).
Last publication: Medda E, Toccaceli V, Fagnani C, Nisticò L, Brescianini S, Salemi M, Ferri M, D’Ippolito C, Alviti S, Arnofi A, Stazi MA. The Italian Twin Registry: An Update at 18 Years From Its Inception. Twin Res Hum Genet. 2019 Sep 26:1-7. doi: 10.1017/thg.2019.75.



The main objectives of ITR project are to estimate the contribution of the genetic and environmental factors to the variability of normal or pathological human traits and to study gene-environment interaction (GxE). Moreover, taking account the non-independence of data within twin pairs, all analyses could be performed on twins as individuals.


Type of study

Cross sectional and longitudinal studies based on twin pairs or individuals. Longitudinal twin studies offer the opportunity to improve the understanding of the pathways behind specific phenotypes.


Title of WP or Activity on inequalities

The Italian Twin registry as a tool for the study of health inequalities and their determinants.


WP/Activity Summary

The Italian Twin Registry is a research tool with great potential in public health. In particular, the information already collected is an important starting point for the study of health inequalities in Italy, while the availability of a sample of subjects that can be easily contacted (by post, e-mail, telephone) is a precious resource for new studies.
This WP aims, through the analysis of the data already collected, to highlight and describe the relationship between social determinants (eg: own or parent’s education level, employment status, area of residence, gender, environmental exposure, level of deprivation in the residence area, degree of urbanization of the area of residence) and health condition or psychological well-being (eg health status, perceived quality of life, use of health facilities or pharmaceutical prescriptions).
Several studies, conducted in different countries, have shown that the twin population does not differ from the general population (singletons). These results, therefore, support the use of the twin population as a “sentinel” population and confirm the possibility of generalizing to the whole population what was observed in twin samples.
Furthermore, the availability of monozygotic (genetically identical) and dizygotic (partially identical, on average they share 50% of the genes) pairs allows us to determine whether, and to what extent, health inequalities can be explained or “confused” by familial or genetic influences.


Expected results

Investigate and describe the main determinants of health inequalities in the Italian population by using the ITR database and exploiting the peculiarities of the twins.


Responsible of the project: Maria Antonietta Stazi (

Responsabile of the WP/Activity on inequalities: Emanuela Medda (

Department/Center: Reference Centre for Behavioural Sciences and Mental Health

Project website: