Adolescent girls appear to be at greater risk of insomnia after they begin menstruation, a study has found, suggesting that hormonal changes play a role in some girls’ development of the sleep disorder.

Researchers found that among more than 1,000 13- to 16-year-olds, nearly 11 percent had suffered insomnia at some point. Insomnia, based on formal clinical criteria, was defined as problems falling asleep or staying asleep at least four times per week for one month or longer.

Typically, the study found, the teens started having sleep disturbances around the age of 11. Before menstruation, girls were about as likely as boys to have insomnia. After they began their menstrual periods, however, girls had more than twice the risk of insomnia as boys.

The findings, published in the journal Pediatrics, suggest that the hormonal changes that come with menstruation contribute to girls’ insomnia risk, according to the study authors.

Such a physiological reason is one of two broad explanations for why menstruation would be related to insomnia, said lead study author Dr. Eric O. Johnson.

The other possibility is that the physical changes that come with puberty, like breast development, create “social pressures” that contribute to sleep problems, explained Johnson, a researcher with RTI International in Research Triangle Park, North Carolina.

However, he said, menstruation was related specifically to problems with staying asleep and getting enough deep sleep. These forms of insomnia are more likely to have physiological causes, whereas problems with falling asleep in the first place can often be stress-related.

In addition, girls’ higher risk of insomnia was not explained by higher rates of depression, which is often marked by sleep disturbances.

Another key finding from the study, Johnson said, was that of all teens who ever suffered insomnia, the large majority - 88 percent - also had symptoms at the time of the study. This, he explained, signals that the problem is lasting for many teenagers.

“Insomnia seems to be common and chronic among adolescents,” Johnson and his colleagues conclude in their report.

Given the consequences of sleep deprivation among teenagers - including blunted mental acuity, poorer school performance, and even poorer physical and emotional health - prevention and treatment may need to become “important priorities,” according to the researchers.

Therapies for insomnia include lifestyle changes to promote sleep - like getting to bed and rising at regular times each day - cognitive-behavioral therapy and sleep medications.

SOURCE: Pediatrics, February 2006.