Teens spend about nine hours in front of a screen, according to a 2015 study from Common Sense Media. Kids aged 8-12 are spending almost six hours a day glued to tablets or phones.

If the average teen wakes up at 7 am and goes to bed at 10 am, that means he is spending nine of his 15 waking hours on a smartphone, tablet or computer. Where does he spend the remaining six hours? At school, most likely.

That 9-hour figure is nearly double the amount of time the average American adult spends on a smartphone.

To make matters worse, a new study has found that lots of screen time equates to poor mental health in teens, particularly girls. Experts recommend limiting screen time to just one or two hours a day at most.

If you're the parent of a screen hog, you know just how difficult it can be to pull teens away from their phones. Here are some tips to limit screen time.

1. Be the Example

Teens have minds and personalities of their own, but they're still developing and paying attention to your habits. Set a good example by limiting your own screen time when you're at home.

If the kids have to follow the rules, you do, too.

Teens will be more likely to follow the screen time rules if everyone has to abide by them. It will also teach your children a lesson in commitment, discipline and restraint. These are all important skills that can be applied to other areas of life.

2. Treat Screen Time as a Privilege

Having a smartphone, tablet or laptop is a privilege – not a right. That's a difficult concept for many teens to accept, as electronics and the Internet are so readily available.

Treat screen time as something that needs to be earned rather than given freely. And make it clear that this privilege can be taken away at any time.

How do you ensure that screen time is viewed as a privilege and not a right? One way is to only allow your teen to enjoy some time on her phone or laptop after she's finished her chores, homework and dinner.

3. Using Parental Controls and Monitoring

Parental controls and monitoring programs can help you keep firm control over your child's screen habits.

For computers, Windows 10 offers a series of parental controls, including screen time settings. The operating system allows parents to choose the hours in which teens may use the computer and for how long. For example, you can allow your teen to use the computer between 6 pm and 10 pm for no more than two hours total.

If the teen tries to access the computer outside of these hours or beyond the designated time limit, a popup will appear that requires an adult to log in to provide access.

Parents can also install monitoring apps on their teens' phones to keep an eye on their activities and gauge how much time is being spent in front of the screen.