Health is the extent to which an individual or group is able: to satisfy needs, to realize aspirations, to change or cope with their environment.
Research had shown that hikikomori have difficulties in coping and poor existentialism. In another word, they were not able to satisfy needs, to realize aspirations nor to change or cope with their environment. We should probably be more conscious about the emotional and social dimensions of health. Hikikomori is definitely a health problem that should not be ignored.
References: 1.) Pencheon D. et.al., Oxford Handbook of Public Health Practice. Oxford University Press 2005. Chapter 1.4, Peter Gentle. Assessing Health Status; 2.) Yong K.F. Exploring Hikikomori-A Mixed-methos Qualitative Research. Hong Kong University, 2008