Need quick information - re: self-report trauma history surveys

["Stephanie Dallam" <sjdscout@xxxxxxxxxxxxx>]

Hi,
I have a time-sensitive question about self-report trauma history surveys.
Sometimes participants fill out most of the items but leave one or more
item(s) blank.  

There are various possible reasons one could imagine for leaving an item
blank.  Does anyone know if this has been systematically studied for trauma
history survey instruments?  

In particular, does anyone know if there is any information on whether
missing responses are more likely to be associated with true "yes" or "no"
answers on trauma history questionnaires (or surveys of other potentially
stigmatizing or personal information)?  That is, if someone is asked to
indicate an experience like rape on a self-report survey form and leaves the
item blank, is this known to be more likely associated with a true "no" or
"yes" response?

Thanks,

Stephanie Dallam