Sleep terrors may have genetic roots

NEW YORK (Reuters Health) - Sleep terrors may run in the family, new research in twins shows.

Dr. Jacques Montplaisir of Sacre-Coeur Hospital in Montreal and his colleagues found that about 40 percent of a child's risk of having these sudden awakenings could be explained by genetics. Some good news for parents is that just half of the children who had sleep terrors at 18 months continued to have them at 30 months.

Sleep terrors are the most dramatic type of arousal disorder, usually occurring abruptly with screaming. The person is confused, disoriented and cannot be consoled. Efforts to wake up the sufferer may make them more agitated. When left alone the person will fall back to sleep, and will not remember the arousal upon waking.

Studies of the prevalence of sleep terrors, which are known to be common in children, have had mixed results. Although the condition is known to peak in childhood and usually disappears before adolescence, it may also occur in adults, Montplaisir and his team report in the current issue of Pediatrics.

To investigate further, as well as to examine the potential genetic roots of the condition, the researchers surveyed the mothers of 390 twin pairs who had been followed since birth as part of the Quebec Newborn Twin Study.

Because identical twins share virtually all of the same genes, while fraternal twins only have about half their genes in common, studying twins allows researchers to compare the effects of genes and environment.

Overall, 36.9 percent of children had sleep terrors (defined as "sudden arousal with screams, sometimes with confusion and sweating") at 18 months of age. By 30 months, only 19.7 percent of the children had sleep terrors.

By comparing the prevalence among the identical and fraternal twin pairs, the researchers determined that 43.7 percent of a child's risk of sleep terrors was genetic 18 months, and 41.5 percent of risk was genetic at 30 months.

Environmental factors that were not shared by the twin pairs were responsible for the remaining risk. While the researchers did not specifically look for such factors, possibilities could include one child having been hospitalized while the other was not, or one having been given a particular medication.

Because the researchers relied on mothers' reports of night terrors, rather than a medical diagnosis, the findings should be interpreted with caution, the researchers add. Nevertheless, they conclude that the "results show that there is a substantial effect of genetics factors in sleep terrors."

SOURCE: Pediatrics, December 2008.