What is Pica?

And we are back at it with our 5th installment in this series of comprehensive reviews. If you haven’t checked the others out, you can find all of them by clicking here. Today’s review discusses yet another eating disorder which was only recently (well, in the past 6 years, but in DSM years, that is “recent”) granted its status as a distinct eating disorder. Let’s take a deep dive and learn more about this peculiar disorder that doesn’t quite seem to fit the mold of any other disorder here.

Definition and Diagnosis

According to the DSM 5, to be diagnosed with pica, a person must display four primary criteria:

  • Persistent eating of non-nutritive substances for a period of at least one month.

  • The eating of non-nutritive substances is inappropriate to the developmental level of the individual.

  • The eating behaviour is not part of a culturally supported or socially normative practice.

  • If occurring in the presence of another mental disorder (e.g. autistic spectrum disorder), or during a medical condition (e.g. pregnancy), it is severe enough to warrant independent clinical attention.

We should note also that pica often occurs with other mental health disorders associated with impaired functioning (severe learning disabilities).

Once a child is over 5 years old, pica becomes more concerning and should signal medical professionals to refer children to experienced behavioral therapists and/or dietitians.  However, the DSM recommends a cutoff as early as 24 months.

The current edition of the DSM moved pica into its own distinct category in an effort to avoid overpopulating the Eating Disorders Not Otherwise Specified (EDNOS) (now called Otherwise Specified Feeding and Eating Disorders, or OSFED) classification.  This move effectively removed any age requirements for diagnosis of the disorder, which is similar to the change seen in classification of ARFID.

Items eaten by individuals with pica often include paper, chalk, soil, feces, and other non-nutritious items (Young, 2010).  The two most commonly eaten items in pica are earth (known as geophagia) and ice (known as pagophagia).

The disorder has been linked to obsessive-compulsive disorder (OCD) because of the compulsive nature of this eating behavior.  Those with pica are fully aware they are deviating from regular dietary practices, and they are often in understanding of the health consequences, yet the behavior persists.

History

Pica dates all the way back to the Greco-Roman civilization, specifically concerning the consumption of dirt and clay (Rose, Porcerelli & Neale, 2000).  The word “pica” comes from pica pica, the Latin word for the magpie bird, a bird with distinct behaviors of ingesting non-nutritive items (Johnson, 1990).

Its first inclusion in medical literature came about back in 1563, in which clay and dirt-eating was described in pregnant women and children (Parry-Jones, B & Parry-Jones, WL, 1992). Like ARFID, pica was initially classified under “feeding disorders in infancy and early childhood” in the DSM-IV.  The current edition of the DSM opted to give pica its own independent diagnostic status due to the severity and distinction of this disease.

Statistics

The epidemiology of pica is still largely ambiguous, as two main factors make it exceedingly difficult to accumulate any meaningful data.  First, unanimity in a definition for pica is still missing (the DSM’s criteria leave a lot to be desired and are not as quantitative as they could be) (Rose, Porcerelli & Neale, 2000).  Second, defining “non-food items” can be difficult, as cultural differences (Boyle & Mackey, 1999; Grigsby, Thyer, Waller & Johnston, 1999) and ambiguously defined food items (such as resistant starches or gums) throw a wrench in what might otherwise be a straightforward answer (Young, Wilson, Miller & Hillier, 2008).

However, there are some generally agreed upon figures.  As the vast majority of pica cases are seen in three specific groups (pregnant women, young children, and those with severe learning disabilities), these are where the most robust numbers lie.  As such, pica likely affects 12-20% of children 6 years old or younger (Murray et al., 2018; Al-Sharbati, Zaidan, Al-Hussaini & Al-Khalili, 2003), 20-28% of pregnant women (Fawcett, EJ; Fawcett, JM & Mazmanian, 2016), and 10% of patients with severe learning disabilities (McAlpine & Singh, 1986).

Etiology and Pathophysiology

Some of the proposed etiologies include:

Cultural expectations

One factor that distinguishes pica from other eating disorders is its widespread and heterogeneous prevalence among different cultures.  From members of the South American Otomac tribe to Tanzanian slaves (Woywodt & Kiss, 2002) to the post-Civil War American South (Parry-Jones, B & Parry-Jones, WL, 1992) to Nigerian tribe members in search of “kanwa” (Morton, 2017), pica’s cultural prevalence is glaring.

Because of its culturally relative status, pica remains hard to diagnose objectively.  For example, pregnant women in Northern India will commonly consume ash, brick, charcoal, clay, and dirt for their positive spiritual benefits (Bhatia & Kaur, 2014).  This same practice seen in, for instance, middle class suburbia in the United States would much more likely point a medical professional towards a diagnosis.

Hunger

The hunger hypothesis was probably the earliest, most primitive of the pica hypotheses.  It states simply that people pathologically consume non-food items when they are hungry and nothing else is available (Bateson & Lebroy, 1978).  This hypothesis originated from The Geography of Hunger, a 1950s work by Brazilian physician and nutrition specialist Josué de Castro (Vasconcelos, 2008).

Micronutrient deficiencies

This is a major etiological theory in the literature. The primary micronutrients we are looking at here are iron, zinc, and calcium. For example, pagophagia is said to often occur during periods of iron deficiency (López, Ortega & de Portela, 2004).  It is hypothesized that consuming ice serves to activate the sympathetic nervous system (or possibly the dive reflex) to prompt vasoconstriction peripherally and improve perfusion.  In other words, blood is more efficiently shunted to the brain (Hunt, Belfer & Atuahene, 2014).

This is further evidenced by population-based studies that have found rates of pica to be significantly correlated with micronutrient deficiencies, specifically iron and ferritin (the iron-containing protein that often serves as a marker of serum iron) (Nchito et al., 2004).  One major meta-analysis found that pica’s correlation with these deficiencies (though still causally nebulous) was on par with other well-established deficiency causes (Miao, Young & Golden, 2015).

Protection against toxins and pathogens

One theory that has circulated in the past decade posits that the non-nutritive eating patterns of pica exist as a fundamental mechanism of protection, especially during the most vulnerable stages of mitosis (human cell replication) and embryonic development, namely pregnancy and early childhood (Young et al., 2008).

In fact, this is a primary reason we believe morning sickness arises in newly pregnant women.  The heightened nausea and emetic response would serve to expel potential teratogens (substances that risk poisoning or injuring the embryo) in the GI tract (Flaxman & Sherman, 2000).

More generally, this potential role of pica could mean certain non-food items would help block dangerous pathogen absorption through one of two vehicles.  The substance could literally bind the pathogen and block absorption, or it could coat the mucosal lining of the tract to prevent absorption this way (Young et al., 2008).

Others

Some other, albeit significantly less researched, theories on the etiology of pica include a possible stress-protective role (Singhi, S; Singhi, P & Adwani, 1981; Bhatia & Gupta, 2009) and dyspepsia (Tijjani et al., 2011).

Dangers

It has been reported that the vast majority of cases of colonic obstruction can be linked to pica (Senol et al., 2013).  Since the nonfood items ingested in pica are not technically digestible and will necessarily cause blockages throughout the lower GI tract, developing some degree of intestinal obstruction is almost guaranteed in anyone practicing pica behaviors for long enough (Anderson, Akmal & Kittur, 1991).

As mentioned, though bidirectional causality is a confounder still (meaning we don’t know whether the pica is causing the micronutrient deficiencies or the micronutrient deficiencies are causing the pica), a huge number of studies have unanimously supported pica’s association with lower hemoglobin, hematocrit, and zinc concentrations (Miao et al., 2015).  Subsequently, it is also a big risk factor for anemia.

Pica has important implications for one’s dental health, and as such, this is an area that dental schools and dental continued education programs are increasingly looking at.  When pica is associated with hard, unrefined, gritty items like sand or rocks, there is a high risk of abfraction (biomechanical wear of the tooth due to undue forces placed upon it), attrition (loss of elements of tooth structure due to tooth-on-tooth friction), and erosion (gradual and sustained loss of tooth tissue at the surface) (Johnson, Shynett, Dosch & Paulson, 2007).

Treatment

It is recommended that any treatment course for pica should begin with attention to any possible intestinal stoppages, heavy metal poisoning, or other GI distress issues. Basic nutritional counseling could be an effective treatment strategy, though much more research is needed.  This also varies greatly depending on which population this is being tailored to. Young children will clearly need a much different approach than pregnant women, for example.

Decreasing exposure to craved substances by reducing access and/or replacing it with edible options of similar physical properties/texture (Matson et al., 2013) can be an effective middle line of defense.  Mild aversion and reinforcement therapy techniques have shown to be at least moderately effective; these have patients associate immediately negative outcomes with the consumption of the nonfood items of choice and then positively reinforce eating the “substitution foods” (Mishori & McHale, 2014).

SSRI protocols are not unheard of here, though efficacy is highly questionable.  The atypical antipsychotic olanzapine and the stimulant methylphenidate have both been used in clinical trials, both to moderately promising success but with too much heterogeneity in findings to recommend any pharmacological line of defense just yet.

Prognosis

Surprisingly little is known about the average prognosis of the course of pica.  This is partially because this depends so greatly on which food items are being consumed and how long the patient has suffered from the disease, and it is partially because the three groups it chiefly affects all have different prognostic patterns associated.  For example, it is not unheard of for pica to spontaneously resolve in pregnant women and children, but it is experienced more chronically on average in those with mental disabilities (Leung & Hon, 2019).

Resources

  • NEDA - The largest national eating disorder advocacy forum, which regularly hosts outreach events, funds important research, and directly helps those affected via their helpline.

  • ANAD (National Association of Anorexia and Related Disorders) - Non-profit corporation that advocates for and seeks to spread awareness of eating disorders, especially anorexia nervosa and bulimia nervosa.

  • AED (Academy for Eating Disorders) - Organization that specializes in ensuring the professional standards of eating disorder research, treatment, and information.

NEDA’s Helpline number is: 1-800-931-2237

References

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  4. Bhatia MS, Gupta R. Pica responding to SSRI: an OCD spectrum disorder? World J Biol Psychiatry 10: 936–938, 2009.

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