The key difference between OCD and post-traumatic stress disorder (PTSD) is that the intrusive thoughts of people with PTSD are of content relating to traumatic events that actually happened to them, whereas people with OCD have thoughts of imagined catastrophes. PTSD patients with intrusive thoughts have to sort out violent, sexual, or blasphemous thoughts from memories of traumatic experiences.
The main difference between OCD and PTSD is that intrusive thoughts in PTSD involve real traumatic events experienced by the individual, while OCD involves imagined disasters. Both conditions require patients to process these thoughts within the context of their experiences.