Here's a fascinating article from India:
A study of skin disorders in patients with primary psychiatric conditions.
Which neatly goes over a "mixed variety of physical and mental illnesses".
Only 2% were diagnosed with DOP, and less than 5% of the skin disorders were psychogenic.
Now, I don't think this group is at all representative of the people who claim to have Morgellons, since it's a sample of people who have a primary psychiatric condition. But the varied nature of the study group is probably representative of the mixed variety of Morgellons sufferers.
Here's a nice quote:
"The skin occupies a powerful position as an organ of communication and plays an important role in socialization throughout life. The interface between dermatology and psychiatry is complex and of clinical importance"