If you’ve got a smartphone, check it. Chances are, it’s flashing a light or showing you an icon to signal a new text, e-mail, Facebook message, or even the archaic missed call. And that feels good. Face it, it’s a bummer when you pick up your phone after a while and no one has pinged you.

Such a bummer, in fact, that people who constantly check for pings joke that they’re addicted to their smartphones. The now-antiquated sounding “Crackberry” play on RIM’s Blackberry (RIMM) was just a precursor to the glowing touch screen devices, begat by Apple’s iPhone (AAPL) in 2007, that everyone seems to be carrying these days. And as researchers are beginning to suspect, the old joke about not being able to put down the phone may not just be funny, but true.

Though Nancy Petry, a researcher at the University of Connecticut Health Center’s department of psychiatry who studies behavioral treatment for addiction says smartphone lovers may not meet the full criteria for having an addiction. “I think people show what people might call addictive tendencies toward things like smartphones,” she says, but notes that there’s no psychiatric diagnosis.

That’s actually a touchy subject in the psychiatric community—not smartphone addiction, per se, but addiction to its content—namely, the Internet. There’s been a recent push in the psychiatric community to include an Internet addiction as a psychiatric disorder.

The difference between an addiction and other kinds of compulsive behavior, loosely, is that addictions cause people do something compulsively even though it’s detrimental to their lives.

Researchers have presented evidence that people are addicted to sex, gaming, and the Internet, but only compulsive gambling will change categories in the fifth version for the main reference book for psychiatric disorders, the Diagnostic and Statistical Manual of Mental Disorders (DSM-V). When the new version comes out in 2013, compulsive gambling will be included in the same section as substance abuse.

How smartphones are slot machines for the brain

Smartphones actually could tap into one of the same pathways in the brain that make slot machines so addictive, according to Judson Brewer, the medical director at the Yale Therapeutic Neuroscience Clinic.  One of the reasons gambling is so addictive is that it taps into a powerful associative learning pathway.

Associative learning means that your brain is trained to make you feel either good or bad after a certain event. Winning a jackpot feels great, so gamblers get a very strong hit of good-feeling chemicals when they win, which makes them want to do it again. “That forms an associative memory,” says Brewer. “Wanting is the stickiness that creates the glue between what you just did and that feeling.”

It turns out that reinforcing that reward intermittently creates a more powerful need than offering a reward consistently. If people hit the jackpot every time they pulled a lever, gambling would be boring. But because they don’t know when the reward is going to come, they want it that much more. Smartphones, in a way, also channel intermittent rewards.

Think about getting pinged—alerted to a new message. You’re not sure when it happens, but when it does, it’s usually something interesting, worth a glance or maybe even an immediate response. A text is no monetary reward, but you can still train your brain to expect one—and crave it.

Pings may access a similar reward pathway to gambling, but when does an annoying habit like checking your Blackberry during a meeting cross into behavior that’s damaging enough to call an addiction?

It doesn’t, according to the overall scientific consensus, though there are dissenters. Among them, are smartphone users themselves. In a survey of 200 students at Stanford University, 34% rated themselves as being addicted to their phones, and 32% of the remaining participants worried they someday would be addicted. Petry, however, says that scientifically speaking, phone addiction simply isn’t on the same level as other disorders. “When you can’t get to your e-mail, you get distraught. If the Internet connection is down, you get angry, but it’s not really destroying your life.”

Researchers have studied compulsive gambling for years, Petry says, and there’s strong evidence that people with the disorder will ruin their lives doing it, even though they want to stop. There’s been less research done on more recent forms of addiction. For something as new as smartphones, Petry says, “there are probably tiny bits of research. But that certainly wouldn’t meet the criteria to say that this is the psychiatric diagnosis.”

One of the tiny bits of research out there is a study by the International Center for Media & the Public Agenda at the University of Maryland. Two hundred students at the College Park campus had to forgo any media for 24 hours—no computers, no smartphones, no TV—and record their experiences. The result is a bunch of qualitative data, and lots of complaining. But most of the complaints related to the loss of the phones. You can chalk it up to college-age kid drama, but some participants wrote some powerful stuff.

One student who had recently purchased a phone running Android, Google’s (GOOG) answer to the iPh0ne said, “I am very attached to it as I am constantly sending and receiving e-mails, checking Facebook, and playing different games or using applications. Our cellphones have become such a large part of our lives, it is the one thing I always have with me at all times.” Another didn’t trust himself not to check his phone for a day. “I literally had to have my friend hide my phone so I wouldn’t check it by accident.”

This study was looking more at how students use digital media in general, not just the device that provides it. While Internet addiction probably won’t make it into DSM-V, the number of researchers proposing that it be included offers some evidence that people use the Internet compulsively. The pairing of content people want so much with a platform that triggers a powerful reward pathway could be trouble, although there probably won’t be enough evidence to make smartphone addiction an official diagnosis for some time. And even when the amount of research on it has substantially increased, Petry says, it may not support a diagnosis.

But if people are worried that they’re texting too much, they probably are. Petry suggests that if you get anxious when you can’t access your smartphone, you should try to limit how you use it. Use it only for work, or just for games and talking to friends.

“The big recommendation is to find things that make you happy other than smartphones,” she says. In 2010? Let’s just hope such a thing exists.