Transitioning techniques can be used to bring up sensitive topics based on previous comments.
To screen for depressive symptoms (SIG-E-CAPS), each can be rhymed off as follows:
"How has your mood affected your life over the past few weeks? For example, how has it affected your sleep? Your interests?... etc"
For patients who seem reluctant to go this way, beginning with, "Do you have any troubles sleeping?" is a good way to go.
It may be a good idea to have screening tools available in the waiting room, for folks to check out, check off, and bring up if they would like.
Psychiatric Review of Symptoms: a Screening Tool for Family Physicians (Am Fam Phys, 1998)
Screening for Mental Health - US non-profit