As for students who cram for a test until the daylight hours, they may find it difficult to get back on track the next morning. Kronauer said since people are most sensitive to light in the evenings, working through the night can wreak havoc with the circadian pacemaker.

"The later you're working, the more you'll feel it," he said.

TV Watching Linked to Adult Diabetes

With school out for summer, many give in to the temptation to catch up with "Jerry Springer" and "Friends." But a recently released study from Harvard University researchers said too much television can be hazardous to your health.

The data, which shows a conclusive link between television watching and risk for adult diabetes, presented last weekend during the American Diabetes Association's annual conference. Researchers found that men who spent 40 hours a week in front of the blue glow were more than twice as likely to to get diabetes than those who watched for less than two hours a week.

"The reason we looked at TV watching and diabetes is because previous studies have found that TV watching is related to weight gain and obesity," said Dr. Frank B. Hu from the School of Public Health, the lead researcher of the study.

Research spanned eight years and followed the exercise and television watching patterns of more than 40,000 men.