“Like Brannan’s symptoms”
The author uses an analogy claim. In this situation, Brannan’s symptoms are being compared to hypervigilance.
“Hypervigilance sounds innocuous, but it is in fact exhaustingly distressing, a conditioned response to life-threatening situations”
A categorical claim is used in this situation because of the fact that it’s listing all of the symptoms of Hypervigilance.
“Imagine your nervous system spiking, readying you as you feel your way along the walls, the sensitivity of your hearing, the tautness in your muscles, the alertness shooting around inside your skull”
Analogy and categorical claim were used in this situation. The feeling of being nervous, sensitivity of hearing, and the tautness in your muscles are being states as symptoms of PTSD. In fact, the author compares the symptoms of being scared and the symptoms of PTSD.
“And then imagine feeling like that all the time”
The author wants you to actually picture yourself feeling these symptoms all the time when trying to figure out the effects of PTSD on a person. I would say this is a recommendation or proposal claim only because the author wants you to actually picture the feeling. This would be a casual claim also because it claims that the people that have PTSD experience the same way all the time.
“Caleb has been home since 2006, way more than enough time for Brannan to catch his symptoms”
This is a casual claim because the author believes that being around someone for a long time can cause them to catch the symptoms.