As I understand pica, it occurs when the body is lacking certain vitamins and minerals so the person craves non-food items. I'm not positive, but I don't think a therapist is the one to talk with about pica. I think it's a medical issue.
Also, some women get pica when they're pregnant. For example, when my aunt was pregnant she had an urge to eat Noxema face cream. Her doctor prescribed some minerals and the urge went away.