New research shows teenagers have been becoming increasingly more sleep deprived over the past two decades.

This phenomenon was found to be most prevalent in female students, racial and ethnic minorities, and students of lower socioeconomic status, Columbia University's Mailman School of Public Health reported.

The study was the "first comprehensive evaluation of recent sleep trends by age and time period for U.S. adolescents." To make their findings the researchers looked at surveys taken of 270,000 adolescents from 1991 to 2012. The study participants were in 8th, 10th and 12th grades, and reported how often they got seven or more hours of sleep. The adolescents reported if they got seven hours of sleep every day, almost every day, sometimes, rarely, or never. The researchers noted that the survey did not control for weekday versus weekend sleep.

The study found ethnic minorities and those whose parents had lower levels of education were less likely to report regularly getting over seven hours of sleep but were more likely to report getting an adequate amount of sleep.

The largest decrease in the percentage of individuals getting at least seven hours of sleep per night was seen among 15-year-olds, which is a crucial time in development. Seventy-two percent of teens in this age group reported regularly getting seven-plus hours of sleep per night in 1991, by 2012 that percentage had fallen to 63.

"Although the underlying reasons for the decreases in hours of sleep are unknown, there has been speculation that increased Internet and social media use and pressures due to the heightened competitiveness of the college admissions process are adding to the problem," Keyes said. "Declines in self-reported adolescent sleep across the last 20 years are concerning and suggest that there is potentially a significant public health concern that warrants health education and literacy approaches."

The findings were reported in a recent edition of the journal Pediatrics.