Criteria for Something to be Considered a Mental Disorder I know this will probably be closed for being broad, but I think it certainly has an answer.

What are the criteria for something to be considered a mental disorder?

Does a disorder need to be observable physiologically? Or is behavior/perception that is far from the norm enough?
This is not just a broad question, it also differs depending on the specific person holding a specific orientation working at a specific clinical/academic setting. For a DSM-V discussion, see "What is a Mental/Psychiatric Disorder? From DSM-IV to DSM-V" by Stein et al.