Many psychologists consider fear of government to be some sort of mental illness.
Rates are highest, but not limited to, those who are disaffected in some fashion, especially those who have a strong personal grudge against the federal government for one reason or another. Onset is acute. With further exposure, the patient becomes increasingly paranoid, and slowly withdrawals from reality. However, mental deterioration is so gradual that the patient is often unaware of it. For instance, in the patient's warped mindset, each new piece of gun-control legislation is rationalized to be one more step in an ultimate plot by the federal government to confiscate guns altogether.