here in the United States yes memory loss is part of the diagnostics definition of what DID is.. here is a link to the the DSM5 dissociative disorders pages.

http://www.dsm5.org/proposedrevision...Disorders.aspx

on this page is a link to each of the dissociative disorders definfition, diagnostic criteria pages.

when you click on Dissociative Identity Disorder it tells you

the new proposed definition diagnostics
Rationale which is why they are proposing these definition diagnostics
a proposed severity testing
the current definition diagnostics used today so people can compare the present way the USA defines DID with the new proposed definition / diagnostics

pertaining to your question...

the proposed revision states...

B. Recurrent gaps in the recall of everyday events, important personal information, and/or traumatic events that are inconsistent with ordinary forgetting.

and the current (DSM IV TR) criterion states

C. Inability to recall important personal information that is too extensive to be explained by ordinary forgetfulness.

where I live and work a side effect is reaction from treatment.. side effect from taking medication for example. but I understand what you mean. if Im correct in thinking you mean is memory loss a symptom that comes with mental disorder, yes that is why its part of the definition diagnostics here in the USA.

the Quizes you find here and other places on the web are not meant for diagnostic purposes. here in the USA it takes more than doing a quiz to be diagnosed with DID. example you can answer yes or no on a quiz of whether you have memory loss but a quiz cant look into your brain and see whether your memory loss is from a seizure disorder and what kind of seizure disorder, quizzes cant tell you if you have Alzheimer's, MS or Parkinson's which also carry the same symptom of memory loss.. so here in the USA it takes many physical tests like EEG, MRI CAT Scans and others, besides doing quizzes..

also the quizzes dont tell you long term, they just tell you how you are at the moment you are taking them,

when I was diagnosed DID I had to have many interviews with a psychiatrist, interview with my physician, medical tests like those stated above and many more, a psychiatric evaluation that included oral and written tests, two weeks inpatient under observation at a mental ward, I also had to release my records for elementary/jr high and high school, mental health records, medical health records....

for some people the process takes two weeks to complete for others it takes a month or more depending upon scheduling of all the physical and mental exams, interviews, scans...