A study by British Scientists found that teenagers who spend too much time on the internet, TV or playing computer games reduce their academic performance.

According to Fox News, the study conducted by researchers from Cambridge University involves 800 students from age 14 to 15. The study found that teenagers who spend one extra hour on their computer, mobile device, and TV screens have two grades worse in exams than those who don't. The study found that physical activity had no effect on the teenagers' academic performances.

Kristen Corder of Cambridge's Centre for Diet and Activity Research said, "We only measured this 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's grades."

Corder co-led the study, which was published in the International Journal of Behavioral Nutrition and Physical Activity. The study found that the ideal average amount of screen time a day is four hours.

One extra hour of screen time at the age of 14 leads to 9.3 fewer exam points at 16, which is equivalent to two grades. Meanwhile students who spend an extra hour of doing homework and reading gets an average of 23.1 more points than those that do not.

As noted by Independent, the authors also concluded that spending extra time on sports activity has no effect on students' grades.

University of Oxford experimental psychologist Andrew Pryzblski is sceptical about how the study interpreted the results, saying that the study is flawed since it didn't take into account the academic prowess of those involved during the start of the research period.

Further research is needed to confirm the link between extra screen time and lower grades. But the scientists advised parents to think twice about letting their children spend too much screen time, especially TV  as it is reportedly the most detrimental among all the different types of screen.