There is no single reason that causes trauma to occur. In the physical sense of the word, it is often down to accidents, such as car crashes or falls from height, that cause traumatic effects on the body. In some senses, inadequate preparation or assessment of the risks will be the underlying cause of such accidents, but, there again, no amount of mitigation can prevent all traumatic events from occurring. Bear in mind, too, that some physically traumatic events occur quite deliberately, such as acts of war, for example. In the psychological sense, traumatic effects seem to be observable in nature
. Some animals will appear to change their behaviours following a traumatic event as though they are traumatised in the way we understand people can be. Opinions differ as to why conditions like post-traumatic stress disorder occur. Still, they may well be bound up in the natural fight or flight state that all animals go through when there is - potentially, at least - an overload of negative stress hormones
, such as cortisol.