Pica is more common than most people expect. In the general adult population, about 5% report eating non-food substances at least once, while roughly 1% do so repeatedly. But prevalence varies dramatically depending on the group: young children, pregnant women, and people with developmental disabilities all experience pica at significantly higher rates.
Prevalence in the General Population
A population-based study of over 2,400 adults found that 5.3% reported pica behavior at some point, while 1.08% engaged in it on a recurring basis. These numbers likely undercount the real prevalence, since many people feel embarrassed about eating non-food items and don’t disclose it to anyone, including their doctors.
Among children in the general population, fewer than 4% meet criteria for pica, according to CDC data. However, pica isn’t diagnosed in children under two years old because mouthing and swallowing non-food objects is considered a normal part of development at that age. A clinical diagnosis requires the behavior to persist for at least one month.
Rates in Children With Developmental Disabilities
Pica is dramatically more common in children with autism spectrum disorder or intellectual disabilities. A CDC study tracking preschool-aged children from 2008 to 2016 found the following rates:
- Children with both autism and intellectual disability: about 28%
- Children with autism alone: about 14%
- Children with intellectual disability alone: about 10%
- General population children: less than 4%
That means a child with both autism and an intellectual disability is roughly seven times more likely to have pica than a typically developing child. The reasons aren’t fully understood, but sensory-seeking behavior, difficulty distinguishing food from non-food items, and communication challenges all play a role.
Pica During Pregnancy
Pregnancy is one of the strongest risk factors. In a study of nearly 2,400 pregnant women in India, about 27% reported eating chalk, clay pots, or raw rice during pregnancy. Similar patterns show up across cultures, particularly in sub-Saharan Africa and South Asia, where eating soil or clay during pregnancy has been documented for centuries.
The cravings often center on earthy or starchy substances. Some researchers have proposed that the body may be responding to nutritional gaps, particularly iron or zinc deficiency, though the evidence on this is surprisingly mixed. A WHO-published case-control study in Iran found no significant association between pica and iron deficiency or anemia in children, suggesting the relationship is more complex than a simple nutrient shortfall.
What People With Pica Actually Eat
The range of non-food items is wide. According to Cleveland Clinic, commonly consumed substances include dirt, clay, or soil; chalk; ice; paint chips; paper; hair, string, or thread; laundry starch; charcoal; soap; eggshells; ash; pebbles; pet food; and coffee grounds. Ice is one of the most frequently reported, and it’s also one of the few that carries minimal physical risk.
The type of substance tends to vary by context. Pregnant women more commonly crave earthy materials like clay and chalk. Children, especially those with developmental disabilities, are more likely to eat paint chips, dirt, or paper. The specific substance matters because it determines the health risks involved.
Cultural Context Changes the Picture
Geophagy, the deliberate eating of soil or clay, has a long history as a cultural practice in parts of sub-Saharan Africa, South Asia, South America, and among Indigenous peoples of the Americas. Some Australian Aboriginal communities eat white clay for medicinal purposes. These practices have traveled with migration: in Britain, geophagy is associated with communities from West Africa and South Asia, with imported Calabash chalk sold in ethnic shops. Similar patterns have been documented among African migrants in Vienna.
This creates a gray area in diagnosis. The DSM-5 specifies that pica should only be diagnosed when the behavior falls outside culturally supported practices. So a pregnant woman eating clay in a community where this is traditional and expected would not automatically receive a pica diagnosis, even though the same behavior in a different context might warrant one.
Health Risks Depend on What’s Consumed
The biggest concern with pica is what the non-food substance does inside the body. Lead poisoning is a well-documented risk, particularly for children eating paint chips in older housing. One study found that among children living in older residential areas, 40.5% had urine tests suggesting lead exposure, compared to 17.8% of children in newer housing. About 9% of mothers in that study reported their children were eating plaster or paint.
Beyond lead, other risks include intestinal blockages from hair, cloth, or other fibrous materials; parasitic infections from contaminated soil; tooth damage from chewing hard objects like pebbles; and poisoning from chemicals in soap, laundry starch, or other household products. Ice, while not toxic, can damage tooth enamel over time.
The risk profile is highly individual. Someone compulsively eating ice faces a very different situation than a child regularly consuming paint chips. This is why identifying what substance is being eaten matters as much as diagnosing the behavior itself.
Why Pica Develops
There’s no single cause. Nutritional deficiencies, particularly iron and zinc, have long been proposed as triggers, and treating those deficiencies sometimes resolves the cravings. But studies have failed to show a consistent link, and many people with pica have perfectly normal nutrient levels.
Stress, anxiety, and obsessive-compulsive tendencies are also associated with pica in adults. In children with developmental disabilities, the behavior may stem from sensory needs, limited ability to communicate hunger or discomfort, or difficulty learning which items are safe to eat. During pregnancy, hormonal changes may alter taste and smell perception in ways that make non-food substances appealing.
Treatment typically involves addressing any underlying nutritional deficiency, behavioral therapy to redirect the eating behavior, and in some cases managing the medical complications that have already developed from the substance being consumed.