I'm not aware of any articles reporting on PTSD specifically for clusters. There is some criteria if the dx of PTSD applies to clusters . Dr Larry Schor brought this up while presenting at a CB meeting. Technically he is correct although there is a visceral reaction to his perspective.
https://www.researchgate.net/project/Study-Title-Cluster-Headache-Investigating-severity-of-pain-suicidality-personal-burden-access-to-effective-treatment-and-demographics-among-a-large-International-survey-sample
He has presented data several times but i don't believe he has published in a peer reviewed journal