New research suggests that the amount of time a teenager spends in front of a television or computer screen correlates with how well they do on their exams, BBC News reported.

Researchers at the University of Cambridge found that each extra hour per day spent watching TV, using the internet or playing computer games during Year 10 is associated with poorer grades at General Certificate of Secondary Education (GCSE) at age 16.

"Spending more time in front of a screen appears to be linked to a poorer performance at GCSE," Dr. Kirsten Corder, first author of the study, said in a statement. "We only measured this behavior in Year 10, but this is likely to be a reliable snapshot of participants' usual behavior, so we can reasonably suggest that screen time may be damaging to a teenager' grades. Further research is needed to confirm this effect conclusively, but parents who are concerned about their child's GCSE grade might consider limiting his or her screen time."

For the study, researchers collected and analyzed data from 845 students who attend high schools in Cambridgeshire and Suffolk, measuring levels of activity and sedentary behavior at age 15 years and then comparing this to their performance in their GCSEs the following year.

Researchers found that screen time was associated with total GCSE points achieved. Each additional hour per day of time spent in front of the TV or online at age 14.5 years was associated with 9.3 fewer GCSE points at age 16 years, The Independent reported. This is the equivalent to two grades in one subject (for example from a B to a D) or one grade in each of two subjects, for example. Two extra hours was associated with 18 fewer points at GCSE.

Screen time and time spent reading or doing homework were independently associated with academic performance, suggesting that even if participants do a lot of reading and homework, watching TV or online activity still damages their academic performance.

The researchers found no significant association between moderate to vigorous physical activity and academic performance.

As well as looking at total screen time, researchers analyzed time spent in different screen activities. Although watching TV, playing computer games or being online were all associated with poorer grades, TV viewing was found to be the most detrimental.

The findings are detailed in the International Journal of Behavioral Nutrition and Physical Activity.