About 4 percent of the American population suffers from schizotypal personality disorder. It is also somewhat more prevalent in men than women. Schizotypal persoanlity disorder represents approximately 1 to 2 percent of all personality disorders diagnosed, according to a large Norwegian study.  As in other personality disorders, more people display some, but not all criteria of the disorder, meaning that their behavior may be notably "different," but they do not qualify for a clinical diagnosis.