Franklin Roosevelt once said, "The only thing we have to fear is fear itself," but unfortunately phobias are a real and persistent part of millions of Americans' lives. These can range from the common, such as acrophobia (fear of heights), arachnophobia (fear of spiders) and claustrophobia (fear of enclosed spaces), to the truly bizarre, including arachibutyrophobia (fear of peanut butter sticking to the roof of the mouth), Bolshephobia (fear of Bolsheviks) and vestiphobia (fear of clothing).
But unlike fears, which are normal responses to danger, phobias are irrational or excessive responses to a danger that is often exaggerated or imagined. According to the American Psychiatric Institute for Research and Education, 7.8 percent of all American adults have phobias. Phobias are the most common psychiatric illness among women and the second most common among men over 25.
Often these phobias become a debilitating part of a person's life. Some of the most common fears, such as social phobia, animal phobias and agoraphobia (fear of unfamiliar settings), force those afflicted to make significant lifestyle changes in order to function normally.
This has led researchers to search for the cause of such fears. Though it has been well-established that phobias are largely hereditary, it was previously unclear which particular factors are inherited. Researchers at the Hopkins School of Medicine, led by O. Joseph Bienvenu, tested whether basic personality traits, such as extraversion and neuroticism, played roles in the development of phobias.
Extraversion refers to a person's tendency to be venturesome, energetic, assertive, sociable and to experience positive emotions. Neuroticism, on the other hand, deals with the propensity to experience negative emotions, such as nervousness, sadness and anger. Earlier studies have suggested that introversion and neuroticism are linked within families to social phobia and agoraphobia, but they do not address whether this link is actually due to common genetics or a shared environment, since children of phobics could easily "learn" the behaviors of their parents.
In order to test this question, the researchers interviewed thousands of sets of twins to determine the causes of social phobia, agoraphobia and animal phobias. Twin studies effectively allow the study of genetic versus environmental factors, as identical twins share both genes and childhood experiences, while fraternal twins share only experiences.
During such interviews, interviewers determined whether the participants possessed fears that included meeting new people, public speaking, going out of the house alone, being in crowds or open spaces, and animal-related fears. These fears were diagnosed as phobias if the fear and related avoidance of the situation interfered significantly with the participant's life.
Not only did the study confirm that low extraversion and high neuroticism were highly correlated with social phobia and agoraphobia in a single person, but the correlation was much higher in identical twins than in non-identical twins, demonstrating that the genetic factors that affect extraversion and neuroticism account in large part for genetic susceptibility to those phobias.
Animal phobias, on the other hand, did not appear to be correlated with extraversion and were only weakly associated with neuroticism. This suggests that such fears are due mainly to environmental factors and may be learned over time.
The ramifications of these results are profound. If scientists can determine the genes that influence neuroticism or introversion, one could also potentially determine the causes of social phobias and agoraphobia. More effective diagnoses of phobias and, potentially, genetic therapy treatments could be developed in order to help those with debilitating fears.
