What Causes Canine PTSD?
Abandonment:
One key study ran in Japan in 2012 after the earthquake in Fukushima. The earthquake resulted in the abadonment of numerous dogs.
Urinary cortisol levels of abandoned dogs from Fukushima and non-disaster canines from Kanagawa were taken and examined, and behaviors of both groups were documented. The results showed extreme stress after ten weeks in the Fukushima dogs than in dogs from Kanagawa. Behavior of the Fukushima dogs was less aggressive, which reveals their stress manifested elsewhere. They also had lower levels of trainability and attachment to others, which is extremely important. PTSD patients have demonstrated impaired learning paired with the inability to bond with others, which draws a connection between C-PTSD and PTSD. The inability to learn and bond could be where some of the stress is manifested, as opposed to aggression, as well.
The Military
Dogs are frequently used in military work and about five percent of them were reported to have Canine PTSD in 2012, though some reports go as high as ten percent. It is the most common cause of Canine PTSD, and as early as 2010, military dogs were being sent home with Canine PTSD. This is not surprising, considering anywhere between 10 to 30% of human veterans return home with PTSD themselves, depending on which war they may have been a part of. Typically, the stress and rigor of military work, the loud nosies, witnessing death on a daily basis, and/or constantly being exposed to fear or anxiety-inducing situations can influence a dog over time, resulting in Canine PTSD. Dogs have also been left behind after the war, determined to be "excess equipment", especially after the Vietnam War. (Ironically, Vietnam War veterans have the highest rate of PTSD: 31%.) Being abandoned--with the combination of seeing such trauma in the military--can result in extreme Canine PTSD, though recent legislation has ensured dogs are not "forgotton" when the war is over. No study has been performed concerning military dogs and Canine PTSD because the disorder is so new.
Abuse:
In a study published in the Journal of Applied Animal Welfare Science in 2014, dogs with a history of abuse were compared against a control group who had no history of abuse. Both groups underwent a behavioral assessment using the C-BARQ (designed to assess canine behavior). The following results were found: abused dogs were more fearful of strange humans and dogs, displayed aggressive behavior, had obsessive behaviors, seeked attention, were hyperactive, and barked persistantly. Most of these behaviors are commonly seen in victims of Canine PTSD. Similarities between the behaviors seen the abuse dogs and dogs with Canine PTSD are aggressive behavior, increased fearfulness, and hyperarousal--which can encompass obsessive behaviors and hyperactiveness. Therefore, this increases the likelihood abused dogs suffer from Canine PTSD. However, the study did not focus specifically on Canine PTSD, but the results can be compared against the symptoms of Canine PTSD to draw a link with abuse and Canine PTSD.