WHEN YOU SLEEP MAY GOVERN MOOD, REPORT SAYS.

Byline: Angela La Voie Knight-Ridder Tribune News Wire

Varying the times you sleep may have a significant impact on your mood, researchers report.

In a new study of 24 men and women, those who slept during the day and were awake at night reported worse moods than people who slept primarily at night.

The findings may help explain the high rates of anxiety and depression reported among shift workers who have irregular sleep-wake patterns, suggested study author Dr. Diane B. Boivin, a research fellow in the circadian, neuroendocrine and sleep disorders section at Brigham and Women's Hospital in Boston.

``It's good stuff ... their conclusions are sound,'' said Timothy H. Monk, director of the human chronobiology research program at the University of Pittsburgh School of Medicine.

While researchers know that ``one of the main symptoms of jet lag and night work is that our mood isn't up to par, we're moody and irritable,'' researchers have not been able to explain this phenomenon, he said.

In the study, the researchers experimented with the study participants' sleep-wake schedules during a two-month period. The participants remained indoors in dim light throughout a portion of the study period because light exposure helps regulate the body's clock, or circadian rhythm, said Boivin, whose findings appear in the February issue of the Archives of General Psychiatry.

The findings start ``to move beyond generalizations to specifics on what happens to circadian rhythms and how those rhythms might affect mood changes ... and we can actually predict some of those mood changes,'' Monk said.

But while the new study is useful in documenting how the body's internal clock and sleep patterns affect mood, ``none of this surprises me,'' said Charmane Eastman, director of the biological rhythms research laboratory at Rush-Presbyterian-St. Luke's Medical Center in Chicago.

No matter how much someone sleeps, an individual will be less happy and less alert and will perform less well at the low point of the body's circadian rhythm, explained Eastman, also an associate professor of psychology at Rush-Presbyterian-St. Luke's.

When you travel across time zones, the body's internal clock readjusts, but when you work the night shift, your body can never fully adjust to your schedule, she said.

Boivin explained that when an individual travels to a new time zone, the body's clock readjusts as an individual realigns the sleep-wake schedule to fit the new daylight schedule.

``Night shift workers have two things against them,'' Eastman said. They work when their body is less alert - when their performance is lowest, they are most prone to accidents and they're moodiest, she said.