Is there research on de-escalation training?

Yes. Numerous studies have researched the methods and outcomes of de-escalation techniques and training, as part of a multi-modal approach to reducing workplace violence.

RAND Europe was commissioned by NHS Improvement (UK) to report on the evidence of de-escalation training programmes in healthcare settings: They included 19 reviews, which covered over 800 unique studies from 1984 to 2017 spanning four settings. The report focuses on individual skills-based training approaches to workplace violence prevention, specifically emphasising de-escalation tactics. See RESOURCES or access link here.