At certain points, we say that there are certain things in life that we cannot go without. This isn't always true, since not having a cell phone will not actively cause someone to cease existing, but it does mean that without intervening forces, we will never give some things up. There are certain extremes, such as cocaine and alcohol, which leave little to doubt about how addictive they are. But there are certain other habits that are more difficult to prove as addictive; for example, someone who is a regular caffeine consumer forced to go several days without the stimulant, will likely have more trouble focusing or staying awake during certain hours, but he is much less likely to suffer hallucinations, violent temper changes, and sweat, than someone addicted to a drug as defined by the FDA. But the more interesting case is video games. There are numerous stories about individuals who have failed to compete in the real life arena because they were busy playing. And several studies have shown that people who spend significant amounts of time playing games show brain function changes similar to those who abuse illegal substances. This is made interesting by the fact that video games are not a substance, but cause the same effect on the brain, including making some people change behavior to extremely violent or neglectful. The question is: should video game addiction be treated as a separate mental disorder?
Reference article: http://www.siliconrepublic.com/comms/item/25321-internet-addiction-is/