Aspergers. Because of the nature of Asperger's disorder, the social interactions they experience are different than the "normal" group. Anxiety, misperception, poor communication, black and white thinking are prominent and these symptoms/characteristics may not always mesh well in a relationship.
Surprised? really? I am not aware of the stats, but it's not too surprising, is it? Aspergers is characterized by reduced empathy, social connectedness, confidence expressed joy -- & by increased anxiety. These are hardly characteristics that would facilitate healthy relationships. Still, many asperger individuals do have lasting marriages. It still comes down to finding a good partner & being a good person.