Almost everyone will experience a traumatic event in their lifetime, any lived experience in which a person experiences a lot of stress can be defined as traumatic . This trauma can effect multiple parts of a persons life, and especially relationships. Trauma has numerous effects on the persons well being both physical and mental and this can ultimately manifest in ones relationships too.
An article from ISTSS, International Society for Traumatic Stress Studies, reports of the effects of trauma on relationships. Check out the article below.
https://istss.org/ISTSS_Main/media/Documents/ISTSS_TraumaAndRelationships_FNL.pdf