UCLA professor of psychiatry Andrew J. Fuligni, UCLA graduate student Cari Gillen-O’Neel, and colleagues report that sacrificing sleep for extra study time, whether it’s cramming for a test or plowing through a pile of homework, is actually counterproductive. Regardless of how much a student generally studies each day, if that student sacrifices sleep time in order to study more than usual, they are likely to have more academic problems, not less, on the following day.

The study findings appear in the current online edition of the journal Child Development.

"No one is suggesting that students shouldn’t study," said Fuligni, the study’s senior author. "But an adequate amount of sleep is also critical for academic success. These results are consistent with emerging research suggesting that sleep deprivation impedes learning."

For the current study, 535 Latino, Asian American, and European American students in the 9th, 10th, and 12th grades were recruited from three Los Angeles–area high schools. They were asked to keep a diary for a 14-day period, recording how long they studied, how long they slept, and whether they experienced two academic problems: not understanding something taught the following day in class and performing poorly on a test, quiz, or homework.

Across the board, the researchers found that study time became increasingly associated with more academic problems, because longer study hours generally meant fewer hours of sleep. In turn, that predicted greater academic problems the following day.

Of course, those students who averaged more study time overall tended to receive higher grades in school. But, said Fuligni, "Academic success may depend on finding strategies to avoid having to give up sleep to study, such as maintaining a consistent study schedule across days, using school time as efficiently as possible, and sacrificing time spent on other, less essential activities."