I still think of hikikomori as being different from other types of shut ins. Despite what the link says, there is a social and cultural aspect to this particular form of reclusive activity. There is very high pressure to achieve in Japan, with extremely high standards. It is also considered shameful not to meet these goals. This drives those who can not achieve to living an underground lifestyle. I went through a period of my life where I literally could not leave the house (or even my room) and would get panic attacks if I did so. Even though social pressure had a big helping hand in this, I still could not consider myself hikikomori. I can identify though.