Lacking determination to be socially active; making minimal to no appearances at group events; intentionally missing and not replying phone calls, text messages and voice mails and avoiding social networks on the internet (AIM, Facebook, Twitter, MySpace, etc.) to the extent where your friends think you're living under a rock.
Often acknowledged as an effect of post-heartbreak/depression and lasts for several months at a time.
Girl: "Where's Jamie been? Is he okay?"
Boy: "He must have caught Patrick Star Syndrome, I haven't heard from him in ages."
Girl: "That girl must have broken his heart, huh?"
Boy: "You bet."