New York, Sep 27 (IANS): Parents, please take note. Researchers have found that when there is a TV or video games in the bedroom, children tend to spend less time reading, sleeping or participating in other activities -- and this can adversely affect their grades.

In addition to affecting their performance in school, TV in the bedroom may also increase their risk for obesity, said the study published in the journal Developmental Psychology.

Children with bedroom media watched programmes and played video games that were more violent, which increased levels of physical aggression, the study found.

"When most children turn on the TV alone in their bedroom, they're probably not watching educational shows or playing educational games," said lead author Douglas Gentile, Professor of Psychology at Iowa State University in the US.

"Putting a TV in the bedroom gives children 24-hour access and privatises it in a sense, so as a parent you monitor less and control their use of it less," Gentile explained.

Bedroom media makes it easier for children to spend more time watching or playing, which displaces other beneficial and healthful activities.

For example, researchers tracked children over a period of 13 and 24 months and found bedroom media (both TV and video games) increased total screen time, which indirectly affected school grades.

The data pointed to one explanation - third through fifth grade students who spent more time watching TV, spent less time reading.

Increased screen time was also associated with higher body mass index, physical aggression and symptoms of video game addiction, according to the study.

"We know from decades of research on addiction that the No. 1 predictor of addiction is access. You can't be addicted to gambling, if there is no place to gamble," Gentile said.

While this study looked specifically at TVs and video games in the bedroom, Gentile expects the effects to be the same, if not stronger, given the access children now have to digital devices.