(PDF sorry)
Key screening questions are basically:
* ever thought about harming yourself?
* recently?
* have you thought of a plan for how you would do it?
* have you taken any actions on that plan?
The farther down they get that list, the more concerned you should be. emergency intervention if they Yes all four.
Many people have dark thoughts but have a fear/preservation instincts that protects them from rash inclinations. But once someone starts acting on their thoughts, they need close attention from someone quick and strong enough to intervene. As noted, though, knowing someone's state requires their willingness to honestly share it, so caregivers need to be trustworthy and be trusted.
Giving someone hope and a way forward can help them walk back from the edge, but being manipulative or deceptive or coercive can push them over.