Pica is a term that refers to cravings for substances that are not foods. Materials consumed by patients with pica include dirt, ice, clay, glue, sand, chalk, beeswax, chewing gum, laundry starch, and hair.
Pica is the craving or ingestion of nonfood items. The cravings found in patients diagnosed with pica may be associated with a nutritional deficiency state, such as iron-deficiency anemia; with pregnancy; or with mental retardationor mental illness. The word picais derived from the Latin word for magpie, a species of bird that feeds on whatever it encounters.
The mental health professional's handbook, the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, text revision (2000), which is abbreviated as DSM-IV-TR, classifies pica under the heading of "Feeding and Eating Disorders of Infancy or Early Childhood." Adiagnosisof pica requires that the patient must persist in eating nonfood substances for at least one month. This behavior must be inappropriate for the child's stage of development. Further, it must not be approved or encouraged by the child's culture.
The cause of pica is not known. Many hypotheses have been developed to explain the behavior. These have included a variety of such factors as cultural influences; low socioeconomic status; deficiency diseases; and psychological disorders.
Malnutrition is often diagnosed at the same time as pica. A causal link has not been established. Eating clay has been associated with iron deficiency; however, whether decreased iron absorption is caused by eating clay or whether iron deficiency prompts people to eat clay is not known. Some cultural groups are said to teach youngsters to eat clay. Persons with iron deficiency anemia have also been reported to chew on ice cubes. Again, the mechanism or causal link is not known.
Eating paint is most common among children from families of low socioeconomic status. It is often associated with lack of parental supervision. Hunger also may result in pica.
Among persons with mental retardation, pica has been explained as the result of an inability to tell the difference between food and nonfood items. This explanation, however, is not supported by examples of nonfood items that were deliberately selected and eaten by persons with limited mental faculties.
Pica, iron deficiency, and a number of other physiological disturbances in humans have been associated with decreased activity of the dopamine system in the brain. Dopamine is a neurotransmitter, or chemical that helps to relay the transmission of nerve impulses from one nerve cell to another. This association has led some researchers to think that there may be a connection between abnormally low levels of dopamine in the brain and the development of pica. No specific underlying biochemical disorders have been identified, however.