Doubling Up on Research Using a Database of Twins

from WSJ.com

One of the biggest puzzles in science is distinguishing what is caused by nature versus nurture. That's why a lab here with a treasure trove of data on twins is increasingly fielding requests from around the world from researchers trying, for example, to uncover causes of dementia and better understand economic behaviors like financial risk-taking.

The Swedish Twin Registry, launched 50 years ago, contains birth data, medical records and other information on nearly 100,000 pairs of twins—believed to be the largest and oldest such resource in the world. The data have spawned over 500 published reports examining various questions about cancer, asthma, family relationships and mental health. Early findings provided valuable evidence linking cigarette smoking with lung cancer, and helped to dispel the so-called refrigerator-mother theory, a popular belief in the 1950s that emotionally frigid mothers were to blame for their children's autism.

Identical twins share all the same genes. So, if a disease is fully genetic-based, both twins should have the same risk of contracting it. More commonly, however, genes and environmental factors both play a role. Recent research found that the identical sibling of a twin with dementia has about a 50% chance of also developing this type of cognitive impairment, indicating that genetics are only part of the cause of the disease. By contrast, fraternal twins and other nonidentical siblings, who share roughly half of the same genes, have about a 25% chance of getting dementia if the other sibling has it.

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