Nightmares have a genetic basis and are strongly linked to mental illness, scientists have discovered. Finnish researchers base their claims on a study of the dreams of 2,276 pairs of identical twins and 4,172 pairs of non-identical twins. According to New Scientist magazine, they found that identical twins are twice as likely to share the trait of having frequent nightmares as non-identical twins.
Nightmares raise the pulse rate and step up metabolism in the brain.
The frequency of nightmares tends to stay roughly the same from childhood through middle age, with some people suffering three or four nightmares a week. Markku Partinen, another member of the team, noted that people with depression and schizophrenia reported more nightmares than healthy people. He speculated that nightmares may be due to abnormal activity in the limbic system - the part of the brain that deals with emotions. The BBC is not responsible for the content of external internet sites.