The above answer is misleading. Study has shown a genetic predispostion, carried by the males. For further information refer to the New England Journal of Medicine, in particular the article on Familial Occurrence of Neurocardiogenic Syncope.
Hi,
How are you?
Neurocardiogenic syncope is by far the most common cause of sudden fainting. It is very rarely life threatening although injuries can occur due to fall. It is not genetic.
However it is important to identify the triggers. Avoidance of triggers are cornerstone of treatment.
Wearing graded compression stockings and beta blockers have been found to be helpful.
http://en.wikipedia.org/wiki/Vasovagal_syncope