PTSD Service Dogs: Triggers
A PTSD Service Dog does not prevent trauma-specific triggers. An example would be a veteran who is triggered by the sound of helicopters, and the dog would not prevent helicopters from coming around.
What a Service Dog DOES do:
A Service Dog for PTSD can help prevent environmental triggers.
The Service Dog can help the handler get more personal space in public, and do so without attracting attention that the handler doesn't want. The dog can be used as a buffer and keeps other people from unexpectedly getting right next to the handler. Thus, the intensity of being out in public can be reduced to a nice lower level...and the handler can feel much better about going out in public again.
Stress alerting. In a stressful situation, it can be easier to see how a dog is reacting (panting, licking, looking away constantly, and other stress-reduction techniques specific to dogs) and thus the handler can realize that both the dog and handler need a break. Also, once the dog is fully bonded to the handler, often the dog will pick up on the handler's stress levels and alert the handler that they are becoming stressed (even before the handler would notice the symptoms in themselves), and in this way, the dog becomes a biofeedback tool. (Also, the dog can be used as an excuse for the handler to removethemselves from the stressful situation.)
Medication reminders. The dog can be trained for the task of reminding the handler to take their medication, thus keeping all the effects that happen when the handler doesn't take their medication regularly.