Fainting at the sight of blood or other outside-the-body triggers may run in families, according to a new study of twins.
About 1 in 4 people will faint in their lifetimes, according to WebMD.
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A study published in the journal Neurology suggests that being prone to passing out may be passed down in our genes. If that's true, and researchers can identify the genes involved, it may point to a way to help the small percentage of people who faint so regularly it interferes with their lives, according to WebMD.
Researchers looked at 51 same-sex pairs of twins where at least one had fainted. The pairs included fraternal and identical twins.
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Results from a phone survey suggested that both identical twins were more likely to have fainted than both fraternal twins, CNN reported.
That suggests a strong genetic component in fainting, "making subjects vulnerable to environmental triggers to result in a faint at a particular moment, such as emotional events, stress, sight of blood, etc.," study co-author Dr. Sam Berkovic, a neurologist at the University of Melbourne, Australia, told CNN.
The risk of fainting not related to outside factors, such as dehydration or heart problems, was also much higher in the identical twins compared to fraternal twins, The Daily Mail reported.