To say that the Internet has revolutionized modern life is like saying that refrigerators keep things cold. It's so obvious by now that even commenting on it seems dated, something that might have been interesting 10 years ago but is now simply taken as fact.

Of course, with every revolution come a few casualties. And in the age of 24-hour cybersurfing, second lives, and a website for just about every vice known to man, addiction specialists are starting to link compulsive Internet use to depression. And like other forms of depression, this uniquely modern form can be rather hard to diagnose.

Remember when the phrase "always on" entered the vernacular? In the late 1990s, it was a luxury to have quick and reliable Internet access in your home; today, it's practically viewed as a right to have it everywhere you go.

I spend several hours online every day; I have to for my work. But while I'm online, I'm not just working: I check email, play Scrabble, look up random topics, peruse old friends' Facebook photos, and absorb an enormous amount of information without seeming to retain much of it. When I get offline, I feel a wave of well-being wash over me. And what happens within 20 minutes? I find myself back online.

I suspect this describes most people I know, including those who work in offices where they are ostensibly "always at work." But are we depressed because of it? We may be, or maybe we spend so much time online because we're depressed. Like most chicken-or-the-egg questions, this is probably the wrong question to be asking. Better we should ask ourselves if our "second lives" are eclipsing our real lives, and if so, are we worse off for it?

Internet addiction and its psychological effects have been studied for years. Since 1995, the Center for Internet Addiction Recovery has been treating people for the affliction, whether self-diagnosed or determined by a doctor. Studies are conducted on Internet addiction every few years, suggesting that nothing we're seeing now is necessarily new. But with broadband, a limitless cyberspace, and handheld devices that make it all just a finger-tap away, Internet addiction may be getting a lot more serious. And it could well be making a lot of people depressed.

In 2007, MacKenzie Funk wrote an article for Harper's about her experience at a treatment facility for Internet addicts in China. There, patients were brought back to Earth after having all but lost their minds from a near-constant online existence. Many of them had stayed up for days at one of China's Internet cafes, glued to role-playing games and developing avatars through programs like Second Life, itself a subject of study by Internet addiction researchers.

And that was already three years ago. Are we, indeed, faced with an even greater problem today?