Korean high school students sleep an average of 5 hours and 27 minutes a night, an hour less than four years ago, with 70 percent acknowledging that they are sleep deprived, a survey suggested Monday.

The poll by the National Youth Policy Institute asked 9,521 elementary and secondary school students about their sleep, rest and causes of stress.

Korean students reported an average of 7 hours and 6 minutes of sleep per night, with elementary school students sleeping for 8 hours and 19 minutes and middle school students for 7 hours and 12 minutes, both down about 10 minutes from 2009, according to the survey.

For elementary school students, 61.6 percent responded that studying at home is the primary cause of their lack of sleep, followed by watching TV and films and listening to music at 60.2 percent.

The majority of middle school students, or 67.6 percent, watch TV and films and listen to music at night, which leads to sleep deprivation.

As for high school students, 52.6 percent lack sleep because they spend time studying at night.

Not enough relaxation, coupled with too much stress, may have resulted in the high rate of suicidal thoughts among the secondary school students.

Notably, 36.9 percent of those attending secondary school answered that they had had suicidal thoughts in the past year due to poor grades (40.4 percent) and family problems (27.6 percent).

Among those surveyed, about 60.5 percent said they had less than two hours of time to relax on weekdays; 29.7 percent said they had less than an hour.

Seven in 10 Korean students are under great stress due to poor grades, and 51.6 percent because of concerns about the future.

By Ock Hyun-ju, Intern reporter (laeticia.ock@heraldcorp.com)