Genetic and physiological. There may be a genetic suscepti bility to a certain category of
specific phobia (e.g., an individual with a first-degree relative with a specific phobia of an-
imals is significantly more likely to have the same specific phobia than any other category
of phobia). Individuals with blood-injection- injury phobia show a unique propensity to
vasovagal syncope (fainting) in th e presence of the phobic stimulus.