Stress about schoolwork, not rowdy behavior, is keeping most of America’s college students from getting a good night’s sleep, according to a new psychological study.

The study, published in the latest edition of the Journal of Adolescent Health, draws its conclusions from a survey of 1,125 students between the ages of 17 and 24 attending an unidentified “urban Midwestern university.” The study's authors -- psychology professors from Virginia Commonwealth University and the University of St. Thomas, in Minnesota -- acknowledge that the sleep habits of young adolescents have already been “extensively documented.” They argue, however, that comparatively fewer studies have examined how these sleep behaviors change when older adolescents enter college, “a time of minimal adult supervision, erratic schedules, and easy access to over-the-counter, prescription, and recreational drugs.”

College students, the study notes, have “chronically restricted sleep.” Only around 30 percent of the students surveyed reported that they were getting at least eight hours of sleep, as most physicians recommend for young adults. On the other end of the spectrum, a quarter of the students reported that they were getting less than 6.5 hours of sleep a night. Overall, the average sleep time was around 7 hours a night.

Students appear to be making up for their lack of sleep from the workweek during the weekend. The average reported bedtime on a weekday at 12:17 a.m. shifted to 1:44 a.m. during the weekends, and the average reported rise time on a weekday at 8:02 a.m. shifted to 10:08 a.m. during the weekends.

It apparently does not take long for college students to get accustomed to their adjusted sleep schedule. The study finds that the average weekday bedtimes and rise times of first-year college students are 75 minutes later than those of a similar cohort of high school seniors.

Sixty-eight percent of the college students surveyed reported that “stress” was the factor that “most interferes with initiating sleep.” The next most popular rationales identified were “temperature” at 10 percent and “light or noise” at 8 percent. More than half of those who reported that “stress” kept them awake at night clarified that the stress was “academic” in nature as opposed to “emotional.”

The authors note that it was surprising to them that stress, “rather than sleep schedule regularity, alcohol or drug use, exercise frequency, or electronics usage” was cited most by the students for their lack of sleep.

Not only did these students report they were not getting enough sleep, but the survey also found that they were getting a poor quality of sleep, as measured by scientific instruments such as the Pittsburgh Sleep Quality Index. Three-fourths of the students noted that they felt “dragged out, tired, or sleepy” once a week or more. In addition, 15 percent said they fell asleep in class once a week or more.

The authors argue that college officials should take note of their findings.

“College students who are consistently getting poor-quality sleep are at risk for problems far more serious than simply struggling to function in daily activities,” the study reads. “As chronic insomnia is a risk factor for major mood and substance abuse disorders, physicians, college healthcare professionals, and residence life workers should be more proactive in screening for sleep difficulties and in articulating the importance of sufficient, restorative sleep in college students’ well-being.”