Do axe-wielding madmen make regular appearances in your dreams? If so blame your genes, say Finnish scientists. They have found that identical twins are twice as likely to share the trait of having frequent nightmares as nonidentical twins. The work has also confirmed a strong link between nightmares and mental illness.
Nightmares raise your pulse rate and step up metabolism in the brain. The frequency of your nightmares tends to stay roughly the same from childhood through middle age, with some people suffering three or four nightmares a week.
Christer Hublin of the University of Helsinki and his colleagues looked at nightmare frequencies in 2,276 pairs of identical twins and 4,172 pairs of nonidentical twins. They found that if one of a pair of identical twins reported frequent nightmares-that is, three or more nightmares per week-there was a 45 percent chance that the other twin would share the same trait. With nonidentical twins, there was only a 20 percent chance. "Your genetic constitution may make you more liable to nightmares," says Hublin.
The findings also link frequent nightmares with mental illness. Examination of the volunteers' medical records showed that people who have frequent nightmares are 15 percent more likely to be hospitalised at least once in their lifetime for mental illness, the researchers reported last week at a meeting on sleep research in New Orleans. "We don't know if it's causative or co-occurring," says Hublin.
Author: Alison Motluk
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