defined as? no. i mean, there are people who casually game, and people who game a lot, all the time but are still perfectly functional, then there are people who take it so far (like the guy in the RoK) who end up dying.
so no
but can gaming become an addiction? yes. i mean, almost anything can be psychologically addictive. my ex was definitely addicted to cannabis... a substance that isn't chemically addictive, but take that boy's weed away from him for a week or more, and you'd watch him get more and more withdrawn, depressed, with explosive anger, he slept a lot, he didn't eat, he was miserable and a drain. almost dysfunctional. reintroduce it and suddenly, he's back to normal. (he went off it for a month at one time and he basically sunk further and further until he couldn't take it anymore)... he had literally every single symptom of psychological withdrawal. there was no room for error there, i, nor his mother, had to be a psychology major to realise he was having severe withdrawal. mind you, he argued to the point of violence that it was simply a craving, not a dependence, that he didn't 'need' it (thus me rolling my eyes and telling him if he "didn't need it" then he could quit for a month... he failed at the contest). ...everyone around him knew better.
in some ways, gaming can be similar. one stops playing, and they become demotivated, overreact to stress and rapid mood changes, depression, etc etc. i mean, it's not impossible.
the problem is, is psychological addiction is not as common.
and also, psychological withdrawal is hard to pinpoint, as many of the symptoms can also be pointed to as simply lack of relaxation. so it's really, really hard to say, and that, i think, would need an actual psychological evaluation, and most of us here wouldn't be qualified to make the call. but video games (like weed, actually) affects your dopamine receptors... you DO get a flood of dopamine when you achieve well in a game, and if there's nothing else in your life that gives you the same rush, it's really easy to see how games can become disastrously addictive to some... ie, a teenage kid in an abusive and/or neglectful household, where his accomplishments aren't acknowledged as important... or, say, an asian student in a competitive environment who is never rewarded for doing well enough in school (even tho they have near perfect marks)... which would explain why gaming psychological addiction may be more prevalent in those regions.
the internet can be addicting, as well. to a crippling degree. i can't say i'm 'diagnosed' but i can draw from myself on this one and say the internet absolutely can and it has less of the dopamine firing-off than games, so i can totally see how games would be. i'm probably absolutely addicted to the internet, to the point i've been late to work on accident as a result, forgo sleeping almost every night, have forgone food and have even forgone cigarettes to keep browsing the internet... i've tried to quit using the internet as much at different times in my life as i realised how pathetic it was, but i get sucked back in every time, no matter how much more accomplished i feel when i'm NOT using the internet as much/often as i otherwise would. it feels really shitty, but it does affect me every fucking night... half the reason i don't play games as often as i'd like is due to this, so yeah... and honestly, at this point, i think the only thing that would quit the cycle is getting professional help. pathetic as shit, and sad, but there you go. mundane shit CAN be addictive. it's almost every fucking day i use the internet and think "i should be drawing" "i should be playing vidya" "i should learn more russian" but two hours later and i'm neck deep in a reddit AMA thread about the USSR or north korea or browsing the consumerist or snopes or some other site i use to "not be on forums all night". this is really anecdotal, but i don't know of any studies about psychological addiction for the internet and video games (and other technology) to draw from... so i'll parallel gaming addiction to my own (probable) internet addiction. because i'm shameless i guess (jk, i'm actually a ball of shame, but anonymity, amirite)
psychological addiction is a kind of addiction that doesn't get a lot of time spent to it, and, just like mental health in general, isn't taken as seriously as 'physical' addictions and health (drug addiction, alcoholism, these are more physical addictions). there is a massive stigma against psychological addiction, which causes it to be seen as 'not as serious'. and because it's pretty much invisible and seems harmless on the outside, a lot of people make fun of it. even people in this thread have made light of it... with the "well that RoK guy is an exception..." but the thing is, is addiction gets much worse the longer it's left unchecked. you have to kill the addiction before it gets that bad, and saying it's only when it gets that bad that it's an addiction is... well, telling enough for how we take addiction and mental health as a non-serious issue.
play responsibly.
tl;dr: defined as addiction? no. can it be an addiction? absolutely, gaming fits almost every check for a high capacity to be psychologically addictive under the right circumstances. but for most, no.
edit: and no, just because gaming doesn't directly enhance a set of skills (other than hand-eye coordination, reaction time and maybe some other minute skills) doesn't mean it is easier diagnosed as an addiction than any other psychological addiction. someone who spends 8 hrs a day drawing and calls out of work on the regular to just "finish one more painting" and who wishes they could stop drawing to hang out with friends or family or do something else productive like learn a new language is just as addicted as the people in those everquest horror stories. that you learn a skill or not isn't part of the diagnosis, that's ridiculous, and would mean that the psychologist in question would be able to denote what is, or is not, a "worthless" activity over a "worthwhile" activity... which would cause a bias in the analyser, which is grounds for malpractice. whether something is worthwhile/worthless has no bearing on the question "is [person] exhibiting signs of psychological addiction to X?" the patient will give worth to their addiction, anyway, that's the fucking nature of addicts of ANY kind, physical or psychological.