s parents pack their children off to college this week, they would be wise to add one more piece of advice to protect the health of their offspring: make sure to get eight or more hours of sleep every night.

Like many college students, Jenny Waller, 21, is something of a night owl. In her first weeks at the University of Michigan a few years ago, Miss Waller rarely went to bed before 3 or 4 in the morning.

"In college," she said, "your mom isn't there to tell you to go to bed, and for me, things only got worse. Within a month, I was staying up all night, going to bed at 9 a.m. and pretty much missing all of my classes. Many nights I would sit with my textbooks, but I couldn't concentrate. I wouldn't let myself get to bed until I finished the work.

"But it was a vicious cycle. The later I stayed up, the worse my concentration got, making studying pretty much impossible. I would read the same paragraphs over and over, and pretty much cried about it."

Three months later, Miss Waller was told that she had clinical depression, and she temporarily withdrew from college.

Her history is not uncommon. In the last few years, mental health professionals have asked whether sleep deprivation plays a role in the increase in cases of depression reported on campuses.

According to a study by psychologists at Kansas State University and published in February in Professional Psychology, the number of college-age students treated for depression has doubled since 1989. The study involved more than 10,000 students at more than 100 colleges.

That incidence is twice the rate for the general population: one in 10 men and one in four women will have a clinical depressive episode in their lifetimes. Since 1989, the number of college students consulting doctors for sleep problems increased even more, some experts say.

"There's no question that college kids are sleeping less than they used to," said Dr. Roseanne Armitage, director of the Sleep and Chronophysiology Laboratory at the University of Michigan Depression Center.

Last year, college students averaged 6 to 6.9 hours of sleep a night, far less than the suggested 8 to 9.25 and down from 7 to 7.5 in the 1980's.

Psychiatrists are not certain whether sleep problems are a potential cause or a symptom of depression. Treating depression with antidepressants is not always as effective for sleep problems as for other symptoms. Some medications like the widely prescribed selective serotonin reuptake inhibitors can actually cause insomnia. Many experts have even succeeded with patients with severe depression for short periods by depriving them of sleep.

The role of sleep disturbances in depression has, however, gained the interest of neuroscientists since a study from the National Institute of Mental Health in 1989 reported that sleep disturbances lasting longer than two weeks increased the risk of developing many psychiatric illnesses, especially depression.

"A good analogy," Dr. Armitage said, "would be having a high serum cholesterol and the risk of heart attacks. Just because you have a high cholesterol level does not necessarily mean you are definitely going to have a heart attack. But it is a definite risk factor. The same could be said for sleep disturbances and the risk of developing depression."

Dr. John F. Greden, chairman of the psychiatry department at the University of Michigan, said: "We have pretty good evidence that staying up late all night and then trying to catch up with an erratic schedule of naps quickly creates a situation called delayed sleep phase insomnia. This is the kiss of death for mood regulation."

Many students stay up until 3 a.m., sleep until 1 p.m., try to catch up with a nap and then do it again night after night, Dr. Greden said. But getting back on schedule for 8 or 9 a.m. classes is difficult. The students' sleep is perpetually disrupted, as if they had jet lag, and especially for those with a vulnerability to depression, the patterns are highly likely to be a risk factor.

Nor are long vacations like summer breaks good ways to catch up.

"We know very little about what transpires during the summer, when most students return home," Dr. Greden added. "But, if sleep problems persist because of untreated depression, students are likely to return back to campus in autumn even more vulnerable."

Dr. Fred B. Newton, the director of student counseling at Kansas State and a co-author of the study published in February, said: "Good mental and physical health requires a semblance of harmony and balance in your life. That includes adequate sleep and diet. College does not always promote this."

Dr. Sherry A. Benton, a psychologist at Kansas State and another co-author of the study, said students today faced more diverse and challenging pressures than students 20 years ago.

"Some academic programs," Dr. Benton said, "consider a student to be a slacker if he or she doesn't stay up all night studying. College is more expensive than ever, and there are more students working jobs to pay tuition, in addition to the usual desires to socialize, pursue extracurricular activities, 24-hour access to the Internet and the enormous pressure for students to get all A's in order to succeed, to get into medical, law or even graduate school. Something has to go, and most often it is sleep."

Dr. Mary Alice Carskadon, a professor of psychology at Brown who is a leading researcher of college students' sleep patterns, said many signs pointed to a connection between insufficient sleep and increasing depression.

"Every study we have ever done over the past decade on high school and college students shows the less sleep they get the more depressed mood they report," Dr. Carskadon said. "It is a persistent and strong association that we are able to measure in all the different ways we have looked at this population's sleep patterns from surveys to sleep diaries to manipulating their sleep in the laboratory.

"At Brown, the median bedtime is 2 a.m. That means half the kids are going to bed later than that, and often these kids cannot stay awake during their classes. We've stopped 8 a.m. classes, and frankly, the 9 a.m. classes are a struggle for many of our students."

Dr. David F. Dinges, chief of the sleep and chronobiology division at the University of Pennsylvania, has conducted studies that show that frequent episodes of depressed moods can at a minimum cause significant problems for students, especially when they are learning concepts and concentrating on homework.

Jodi Keller, 19, an undergraduate at Michigan, attributes her first serious episode of depression to a lack of sleep and the overcrowded schedules that most students accept as normal routine.

"When short of time," Ms. Keller said, "it's always sleep that I sacrifice first. I can't remember how many all-nighters I have pulled in order to complete my schoolwork and get good grades."

Another Michigan undergraduate, Victoria Chien, 21, has been treated for serious episodes of clinical depression since she was 17. Miss Chien said, "When I don't get adequate rest, my depression becomes much more severe."

Nevertheless, she remains active in the late-night culture.

"Sleep deprivation," Miss Chien said, "is a pretty big problem for me. I try to make it up over the weekends, but it doesn't help much."