baby twins

Why Twins?

Twin research is an extremely powerful tool for understanding how genes, behavior, and environment affect health and well-being.

Identical Twins

Identical twins share virtually all of the same genes (that is, the same DNA). Similarities between identical twins may be due to genetic factors, while any differences must have a non-genetic origin.

Fraternal Twins

Fraternal twins share about half of their DNA. Differences between fraternal twins may be due to either genetic or non-genetic factors.

Studies that examine differences across both fraternal and identical twin pairs can enhance our understanding of how we stay healthy and why we get sick. For decades, twin research has helped to uncover clues to the origins of many common medical and behavioral conditions, such as depression, alcoholism, Parkinson’s disease and Alzheimer’s disease. Twin studies have produced invaluable insights into conditions as diverse as multiple sclerosis, cardiovascular disease, type II diabetes, and many more.

Not so long ago, many people believed that autism was caused by bad parenting, that social factors caused schizophrenia, and that obesity was due to a lack of will power. By studying twins, we now know that all three conditions are strongly influenced by genes.

These examples demonstrate the value of twin studies in medical and behavioral health research. Twin studies hold great promise to continue to provide significant discoveries about many common health conditions. Large numbers of twin pairs are needed to conduct this research.

A twin registry is a database containing information about twins who are interested in participating in health and behavior-related research. Many countries around the world, including Australia, England, Finland, the Netherlands, Norway, and Sweden, have created large twin registries. The Washington State Twin Registry aims to be one of the largest twin registries in the United States. We partner with twin researchers around the world to study health-related topics such as pain, sleep, immune function, eating behaviors, aging, physical activity and environmental exposures.