Most physicians connect pica to the body's deficiency in iron or zinc, while others consider emotional disturbances such as poverty, neglect, or delays in mental or physical development.
Often pregnancy triggers pica, with symptoms going away as fast as they appeared once the woman is no longer pregnant.
You may have heard of people eating dirt or clay. This is geophagia, a specific type of pica. But some cultures believe eating dirt improves fertility and it is often thought this myth drives this behavior, not an actual craving.
It is important to note that no matter what odd substance is eaten, none of them provide the iron or zinc the body is lacking. For that reason, if you suspect you may suffer from pica, or you know somebody who does, you should see your doctor for a proper diagnosis.