Functionally, these neurons are either motor (conducting impulses that will cause activity such as the contraction of muscles) or association (conducting impulses and permitting 'communication' between neurons within the central nervous system).
The scant research that has been done on the causes of pica suggests that the disorder is a specific appetite caused by mineral deficiency in many cases, such as iron deficiency, which sometimes is a result of celiac disease or hookworm infection.
Doctors use the term pica to describe craving and chewing substances that have no nutritional value â such as ice, clay, soil or paper. Craving and chewing ice (pagophagia) is often associated with iron deficiency anemia, although the reason is unclear. At least one study indicates that ice chewing might increase alertness in people with iron deficiency anemia. Less commonly, other nutritional problems may cause you to crave and chew ice.