still learning. I agree with both dr. Eriquez and dr. Hazlett. It can hard to tease environment vs genetics apart. Because so many people with ptsd have had early experiences of trauma, there is significant possibility that their related gene pool (relatives) may also have been traumatized. We still have a lot to learn about ptsd.
Yes and no. Certain people are more susceptible to ptsd- such as people with anxiety disorders or depression, or a family history of same. Both of them are inherited disorders. So, indirectly ptsd may be heritable. But there is still the element of severe environmental stress as a necessary component of ptsd.
It isn't clear yet. Ptsd has become a broad category of disorders and is in danger of being an imprecise diagnosis. Most studies using accepted criteria have not shown genetic links. Some sources of stress are combat, sexual abuse, witnessing or experiencing traumatic events with severe injuries or even death. It remains unexplained how two people experience the same trauma at the same time and only one develops ptsd.
No. it is environmentally induced by severe trauma.