Studying late into the night actually makes your academic performance worse the next day.
Regardless of how much a student generally studies each day, it seems, giving up sleep for more study time is counterproductive.
"No one is suggesting that students shouldn't study," says UCLA professor of psychiatry Andrew J. Fuligni.
"But an adequate amount of sleep is also critical for academic success. These results are consistent with emerging research suggesting that sleep deprivation impedes leaning."
The study involved asking 535 students in the ninth, 10th and 12th grades to keep a diary for a 14-day period. They recorded how long they studied, how long they slept and whether or not 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.
"At first, it was somewhat surprising to find that in the latter years of high school, cramming tended to be followed by days with more academic problems," says graduate student Cari Gillen-O'Neel.
"But then it made sense once we examined extra studying in the context of sleep. Although we expected that cramming might not be as effective as students think, our results showed that extra time spent studying cut into sleep. And it's this reduced sleep that accounts for the increase in academic problems that occurs after days of increased studying."