I like this rule of thumb to know if a behavior can be a psychiatric disorder: "when it interferes with normal functioning". It's purposely vague and subject to interpretation but it's a good first filter.

  For an addiction X, you can ask questions like: 
  * do I think about X most of the time
  * would I choose X over family/friends/health
  * when engaged in another activity, do I want it to be done quickly so I can go back to X
  * do I feel distressed when I can't do X
  * ...

Looking years ago, my younger self has been addicted to WoW before realizing how little joy the game sparked when playing. And one day I just did not launch it and I was done with it. I certainly feel lucky to have been bored by the game before it did too much damages. Other additions are not so kind on the health/mind/wallet.