The total score (fear and avoidance for all 24 items) should be interpreted as follows:
<50 = mild (clinically insignificant) social anxiety
55-65 = moderate social anxiety
65-80 = marked...
Neurotic anxiety is a type of anxiety that the object doesn't exist. i.e: your professor is a cold one, without smile, and suddenly you feel that he is angry toward you, and you're being anxious to...
Typically, it is because you were genetically predisposed for it. It's caused by an imbalance in your biological system, causing your nervous system to react too frequently, or too strongly.