The tendency to faint can be inherited genetically. But the predisposition for fainting to be caused by stress or exposure to seeing blood is not inherited .
Fainting or vasovagal syncope is a brief loss of consciousness when the body reacts to certain threats, and it usually occurs in one in four people. After studying 44 families, Samuel Berkovic and his colleagues at the University of Melbourne (Australia) showed that a single gene, present on chromosome 15, could cause the tendency to faint to be transmitted from parents to children. However, whether the cause was the sight of blood, undergoing a medical procedure in the hospital, an injection, feeling pain, being afraid or standing for a long time turned out not to be hereditary, as the researchers concluded in the journal Neurology .
