The severity of PTSD can be increased by a number of factors, including: Experiencing or witnessing a traumatic event. Experiencing repeated exposure to traumatic events. Having a history of trauma or abuse. Having a mental health condition, such as depression or anxiety, that makes the person more vulnerable to PTSD. Having a low level of emotional stability. Having a strong sense of self-identity or self-worth. Having a difficult relationship with a caregiver or support system.