It's easy to see why social networking sites like Facebook are so popular -- they connect friends and family and offer instant peeks into the lives of others. But if you're not careful, Facebook can become addictive and hardcore users have reported "zoning out" for hours at a stretch looking at pictures, checking profiles and sharing links.

Yes, Facebook addiction is real. In fact, a Norwegian study suggests the symptoms of Facebook addiction resemble those of drug and alcohol addiction, as well as chemical abuse. The researchers have even developed the Bergen Facebook Addiction Scale -- the first to be scientifically validated -- to measure the severity of Facebook dependency:

The Bergen Facebook Addiction Scale

To do this test, rate each of the following item: (1) Very rarely, (2) Rarely, (3) Sometimes, (4) Often, or (5) Very often.

• You spend a lot of time thinking about Facebook or plan use of Facebook.
• You feel an urge to use Facebook more and more.
• You use Facebook in order to forget about personal problems.
• You have tried to cut down on the use of Facebook without success.
• You become restless or troubled if you are prohibited from using Facebook.
• You use Facebook so much that it has had a negative impact on your job/studies.

If you score "often" or "very often" on at least four of the items, it may suggest that you have a problem, says lead researcher doctor of psychology Cecilie Schou Andreassen.

Facebook addiction stats

So who's more likely to be addicted to Facebook? "It occurs more regularly among younger than older users. We have also found that people who are anxious and socially insecure use Facebook more than those with lower scores on those traits, probably because those who are anxious find it easier to communicate via social media than face-to-face," says Andreassen. Women and the extroverted are also more likely to develop an addiction to Facebook.

If you're guilty of spending too much time on Facebook, here's how to cut back:

Set a time limit. An hour a day on Facebook is more than enough time to catch up with others for most people.

Limit the number of automatic feeds and status updates you receive to close friends and family members. Do you really need updates and news feeds from old acquaintances and people you hardly talk to?

Turn off email notifications. Ask your friends to send important messages via text, phone or email instead.

Delete the Facebook app from your phone. If your friends need to reach you while you're outside, ask them to call you.