A survey of a large clinic population reported that 75 percent of 12-month-old infants and 15 percent of 2- to 3-year-old toddlers placed nonnutritive substances in their mouth. Pica is more common among children and adolescents with mental retardation. It has been reported in up to 15 percent of persons with severe mental retardation. Pica appears to affect both sexes equally.

Pica is most often a transient disorder that typically lasts for several months and then remits. In younger children, it is more frequently seen among children with developmental speech and social developmental delays. A substantial number of adolescents with pica exhibited depressive symptoms and use of substances. Several theories have been proposed to explain the phenomenon of pica, but none has been universally accepted. A higher-than-expected incidence of pica seems to occur in the relatives of persons with the symptoms. Nutritional deficiencies have been postulated as causes of pica; in particular circumstances, cravings for nonedible substances have been produced by dietary insufficiencies. For example, cravings for dirt and ice are sometimes associated with iron and zinc deficiencies, which are corrected by their administration. A high incidence of parental neglect and deprivation has been associated with cases of pica. Theories relating children’s psychological deprivation and subsequent ingestion of inedible substances have suggested that pica is a compensatory mechanism to satisfy oral needs.

Eating nonedible substances repeatedly after 18 months of age is usually considered abnormal. The onset of pica is usually between ages 12 and 24 months, and the incidence declines with age. The specific substances ingested vary with their accessibility, and they increase with a child’s mastery of locomotion and the resultant increased independence and decreased parental supervision. Typically, young children ingest paint, plaster, string, hair, and cloth; older children with pica may ingest dirt, animal feces, stones, and paper. The clinical implications can be benign or life threatening, depending on the objects ingested. Among the most serious complications are lead poisoning (usually from lead-based paint), intestinal parasites after ingestion of soil or feces, anemia and zinc deficiency after ingestion of clay, severe iron deficiency after ingestion of large quantities of starch, and intestinal obstruction from the ingestion of hair balls, stones, or gravel. Except in persons with mental retardation, pica usually remits by adolescence. Pica associated with pregnancy is usually limited to the pregnancy itself. The DSM-IV-TR diagnostic criteria for pica are given in Table 41-1.

No single laboratory test confirms or rules out a diagnosis of pica, but several laboratory tests are useful because pica has frequently been associated with abnormal indexes. Levels of iron and zinc in serum should always be determined; in many cases of pica, these levels are low and may contribute to the development of pica. Pica may disappear when oral iron and zinc are administered. A patient’s hemoglobin level should be determined; if the level is low, anemia can result. In children with pica, the lead level in serum should be determined; lead poisoning can result from ingesting lead. When a child’s lead level is high, this condition must be treated.

The differential diagnosis of pica includes iron and zinc deficiencies. Pica also can occur in conjunction with failure to thrive and several other mental and medical disorders, including schizophrenia, autistic disorder, anorexia nervosa, and Kleine-Levin syndrome. In psychosocial dwarfism, a dramatic but reversible endocrinological and behavioral form of failure to thrive, children often show bizarre behaviors, including ingesting toilet water, garbage, and other nonnutritive substances. A recent case report presented an association of pica with hypersomnolence, lead intoxication, and precocious puberty. Precocious puberty implicates the hypothalamus as a site for at least part of the dysfunction. Lead intoxication is known to be associated with pica as well as several other neuropsychiatric abnormalities in memory and cognitive performance. A few children with autistic disorder and schizophrenia may have pica. For children who exhibit pica along with another medical disorder, both disorders should be coded according to DSM-IV-TR.

In certain regions of the world and among certain cultures, such as the Australian aborigines, rates of pica in pregnant women are reportedly high. According to DSM-IV-TR, however, if such practices are culturally accepted, the diagnostic criteria for pica are not met.

The prognosis for pica is usually good because in children of normal intelligence it generally remits spontaneously within several months. In childhood, pica usually resolves with increasing age; in pregnant women, pica is usually limited to the term of the pregnancy. In some adults, however, especially those with mental retardation, pica can continue for years. Follow-up data on these populations are too limited to permit conclusions.

The first step in the treatment of pica is determining the cause whenever possible. When pica is associated with situations of neglect or maltreatment, these circumstances naturally need to be altered. Exposure to toxic substances, such as lead, must also be eliminated. No definitive treatment exists for pica; most treatment is aimed at education and behavior modification. Treatments emphasize psychosocial, environmental, behavioral, and family guidance approaches. An effort should be made to ameliorate any significant psychosocial stressors. When lead is present in the surroundings, it must be eliminated or rendered inaccessible or the child must be moved to new surroundings.

Several behavioral techniques have been used with some effect. The most rapidly successful technique seems to be mild aversion therapy or negative reinforcement (e.g., a mild electric shock, an unpleasant noise, or an emetic drug). Positive reinforcement, modeling, behavioral shaping, and overcorrection treatment have also been used. Increasing parental attention, stimulation, and emotional nurturance may yield positive results. One study found that pica was negatively correlated with involvement with play materials and occurred most frequently in impoverished environments. In some patients, correcting an iron or zinc deficiency has eliminated pica. Medical complications (e.g., lead poisoning) that develop secondarily to the pica must also be treated.