From time to time, you hear people make the tongue-in-cheek assertion that they're "addicted" to Facebook. But recent data suggests that there might be some truth to such statements.

A group of researchers from the University of Milan and the Massachusetts Institute of Technology (MIT) identified chemical reasons at the root of the pervasive need to check social networks, Boy Genius Report has learned.

They found that users exhibit physical and psychophysiological responses when they log onto Facebook, similar to the sensations experienced by people when they play an instrument or engage in some kind of creative activity.

Researchers monitored 30 subjects ages 19-25 as they looked at photos of nature, tried to solve math problems, and perused Facebook. They recorded physical reactions including skin conductance, blood volume pulse, electroencephalogram, electromyography, respiratory activity, and pupil dilation to uncover a pattern.

The study says: "Statistical analysis of the psychophysiological data and pupil dilation indicates that the Facebook experience was significantly different from stress and relaxation on many linear and spectral indices of somatic activity. Moreover, the biological signals revealed that Facebook use can evoke a psychophysiological state characterized by high positive valence and high arousal."

It added that it's possible users reach a "positive affective state" when they access their social networks.

The report comes the same week that a University of Chicago study found Facebook can be more addictive than cigarettes or alcohol.

With Facebook boasting 845 million users and Twitter at around 300 million, this research could be part of the reason for their enormous numbers. In fact, the researchers indicated that people seek out sites like Facebook and Twitter to receive this type of satisfaction, which has in turn, boosted their growth.

There's been no shortage of Facebook studies lately. Another report released last week found that those with a low self-esteem could suffer more by using the site, as posting negative items to Facebook often makes them appear less likable to their friends.

In other Facebook news, the company last week filed for a $5 billion IPO. For more, see What a Facebook IPO Means For Users, Facebook IPO: What They're Saying, How Much Are Facebook Execs Making?, and the slideshow below.