Giving children melatonin before surgery can significantly reduce the occurrence of delirium after surgery, research suggests.

The prospect of surgery can cause intense anxiety leading up to the surgery. While some amount of stress is normal, extreme anxiety before surgery can contribute to what doctors call "emergence delirium" — distressing behavior changes such as crying and thrashing that may surface immediately upon "waking up" from anesthesia.

Immediate post-surgery delirium can also lead to problems long after the surgery, such as the onset of nightmares, bed wetting and separation anxiety.

The new study, published in the journal Anesthesiology, shows that pre-surgery melatonin reduces post-surgery delirium, but not anxiety, in children having anesthesia and surgery.

"Studies conducted in adults have revealed that oral administration of melatonin before surgery beneficially reduced anxiety levels, but relevant similar treatment data for children undergoing anesthesia and surgery are limited," Dr. Zeev N. Kain from University of California, Irvine, noted in a statement.

Two recent studies reported that melatonin was as effective as midazolam, a sedative widely used to ease preoperative anxiety, in reducing preoperative anxiety in children, but there were methodological issues with both studies.

In their study, Kain's team investigated the effects of melatonin on reducing preoperative anxiety and delirium in 148 children undergoing anesthesia and surgery.

Children treated with midazolam showed significantly less anxiety than did children treated with melatonin, they report.

In contrast, children treated with melatonin showed a reduction in the occurrence of delirium after surgery.

"As 3 million children undergo surgery in the U.S. each year, these findings reveal noteworthy health care and treatment implications," Kain said.