Pica is most common in people with developmental disabilities, including autism and mental retardation. Pica may also occur in adults who crave a certain texture in their mouth. The causes of pica is thought to be a biochemical deficiency and more frequently iron deficiency.  Iron deficiency (or "sideropenia") is the most common known form of nutritional deficiency, such as iron or zinc, that may trigger specific cravings.

 Eating of clay or soil and the ingestion of starch may be culturally based and is regarded as acceptable by various social groups. Clay eating and starch eating are seen in the United States in some southern, rural, and African American communities, primarily among women and children. Starch eating, in particular, is frequently started in pregnancy as a treatment of morning sickness, and is seen most often in pregnant and postpartum females.

 Individuals with mental retardation and developmental disabilities in particular, may also display this behavior.  The traditional view is that the occurrence of pica is a learned behavior maintained by the consequences of that behavior. Maternal deprivation, parental separation, parental neglect, child abuse, and insufficient amounts of parent/child interactions have been associated with pica. Treatment options include: discrimination training between edible and nonedible items, self-protection devices that prohibit placement of objects in the mouth, sensory reinforcement involving screening (covering eyes briefly), contingent aversive oral taste (lemon), contingent aversive smell sensation (ammonia), contingent aversive physical sensation (water mist), brief physical restraint, and overcorrection (correct the environment, or practice appropriate alternative responses).

The common causes and risk factors of Pica include nutritional deficiencies, cultural and familial factors, stress, low socioeconomic status, nondiscriminating oral behavior, and possibly and underlying biochemical disorder or iron deficiency.

The signs and symptoms of Pica include eating nonnutritive substances for a period of at least 1 month, continuing to eat nonnutritive substances which is inappropriate to the developmental level, and this behavior occurring as a culturally sanctioned practice.

Treatment emphasizes psychosocial, environmental, and family guidance approaches. Other successful treatments include mild aversion therapy (associating the pica behavior with bad consequences or punishment) followed by positive reinforcement for appropriate eating.

Medications may help reduce the abnormal eating behavior, particularly if pica occurs in the course of a developmental disorder such as mental retardation or pervasive developmental disorder.