Public speaking was the most common fear for twin women in Virginia

Back in 1992 the Archives of General Psychiatry published an article written by K. Kendler, M. C. Neale, R. C. Kessler, A. C. Heath, and L. J. Eaves titled Genetic Epidemiology of Phobias in Women (Interrelationship of agoraphobia, social phobia, situational phobia, and simple phobia). You can find an abstract at PubMed, or read the full text here.

They asked a sample of 2163 women who were in the Virginia Twin Registry a series of 16 questions about four categories of unreasonable fears that were severe enough to interfere with their lives (phobias), and listed their results in Table 1. I’ve shown those results above in a bar chart. (Click on it to see a larger, clearer view). Those fears were grouped into four categories:

AGORAPHOBIA
Being in Crowds - 6.6%  
Going out of the house alone - 4.1%
Being in open spaces 0.9%

ANIMAL PHOBIA
Snakes - 5.5%
Spiders - 3.3%
Bats - 1.6%
Insects - 1.0%

SITUATIONAL PHOBIA
Other high places - 7.4%
Airplanes - 4.7%
Other closed places - 3.7%
Bridges - 3.1%
Tunnels - 2.9%

SOCIAL PHOBIA
Giving a speech - 9.4%
Meeting new people - 4.4%
Using public bathrooms - 1.9%
Eating in public - 1.6%

The most common fear was giving a speech (social), followed by other high places (situational), being in crowds (agoraphobia), snakes (animals), and airplanes (situational).

They did a very detailed analysis, which I’m not going to try to summarize here, to find influences of genetic and environmental risk factors,. An image of the Kessler Twins came from Wikimedia Commons.