What causes PTSD?

Answer 1

Trauma (infringement or neglect/abandonment based, as there are two types). Specifically, the higher risk of debilitating symptoms will come not only from a emotional reactivity predisposition (diathesis-stress model), but also from a magnification factor kind of thing of the type of trauma. For instance, if it was pervasive, highly personal, and permanent (total loss of control) these will accelerate a "learned helplessness" response (a la Martin Seligman's theory) and accerbate the trauma effects and severity of the resulting PTSD.

Answer 2

Virtually any trauma, defined as an event that is life-threatening or that severely compromises the physical or emotional well-being of an individual or causes intense fear, may cause PTSD. Such events often include either experiencing or witnessing a severe accident or physical injury, receiving a life-threatening medical diagnosis, being the victim of kidnapping or torture, exposure to war combat or to a natural disaster, exposure to other disaster (for example, plane crash) or terrorist attack, being the victim of rape, mugging, robbery, or assault, enduring physical, sexual, emotional, or other forms of abuse, as well as involvement in civil conflict. Although the diagnosis of PTSD currently requires that the sufferer has a history of experiencing a traumatic event as defined here, people may develop PTSD in reaction to events that may not qualify as traumatic but can be devastating life events like divorce or unemployment.