Great Question. Ptsd falls under the class of anxiety disorders. It is interesting that you asked if it is a behavioral disorder. I treat primarily complex ptsd. My combat ptsd patients have hyper-responsive fight or flight reactions. Irritability, high levels of anger & aggression can be very problematic. Ptsd is a destroyer of marriages & families. Road rage & violence when dissociated are major issues.
Threat of death. PTSD is a post trauma reaction to being in the situation of impending real or perceived loss of life, or inability to is scape. Examples of this would come from being in combat situations, or severe physical or sexual abuse. There are degrees of PTSD, it is not a matter of either the patient does or does not have it, it's not all or none.
PTSD. It is classified as an Anxiety Disorder.