I take Effexor for the anxiety and Seroquel for the intrusive thoughts...well, both of them help the intrusive thoughts I guess. My other meds I can skip and not suffer immediately but either if those two if I miss more than a dose I am a PTSD mess.
It does seem to be different for each person though. I had to go through basically every antidepressant there is to figure out that Effexor is the best one for my issues.