The cause of pica behavior has eluded researchers for centuries. Sayetta describes several theoretical approaches that attempt to explain the etiology from nutritional, sensory, physiologic, neuropsychiatric, cultural, or psychosocial perspectives. Nutritional theories are most commonly cited, which attribute pica to specific deficiencies of minerals, such as iron and zinc. Many studies describe patients with low iron or zinc levels whose pica behavior diminishes with iron or zinc replacement, although the empiric evidence for zinc is less convincing than it is for iron. It is postulated that the red clay in southern United States is used because of its high iron content, although clay has been shown to be an iron chelator and can aggravate the problem.
The sensory and physiologic theories center on the finding that many patients with pica say that they just enjoy the taste, texture, or smell of the item they are eating. Geophagia has been used to alleviate nausea by some patients and can give a sense of fullness to patients who are trying to lose weight. A neuropsychiatric theory is supported by evidence that certain brain lesions in laboratory animals have been associated with abnormal eating behaviors, and it is postulated that pica might be associated with certain patterns of brain disorder in humans.
Iron deficiency and pica have been reported in association with celiac disease in childhood.[11,12] Santos and Werlin describe 4 patients who each complained of vague abdominal symptoms of intermittent pain and loose stools. All patients required biopsy to confirm the diagnosis of celiac disease. The gastrointestinal symptoms, pica symptoms, and anemia all resolved with institution of a gluten-free diet. The authors believed that, in these cases, the pica was secondary to the iron deficiency, and the anemia was due to malabsorption. Cases such as these lend support to the theory that pica results from a low iron state.
Psychosocial theories surrounding pica have described an association with family stress.[3,8] Edwards et al found that pagophagia was associated with a smaller social support network, and they hypothesized the behavior to be a method of alleviating stress. In addition, many pregnant women in that study stated that eating freezer frost or ice helped during stressful times.
Addiction or addictive behavior has also been suggested as one possible explanation for pica behavior in some patients. The evidence to support this view is that pica often persists after the physiologic cause is alleviated. If iron deficiency leads to pica, the pica behavior should cease once iron is replaced. Cessation of pica behavior with iron replacement does not happen often, however. Whether continued pica behavior constitutes an addiction or simply a learned pattern of behavior is unclear.
Recently, there has been some evidence that pica is a part of the obsessive-compulsive disorder (OCD) spectrum of diseases, which would lend support to neuropsychiatric theories. Case reports describe patients with severe mental retardation and OCD patterns, as well as patients of normal intelligence with OCD.[15,16] Stein et al describe 5 patients who were examined at outpatient anxiety disorder and OCD clinics. These patients described their pica behavior as one of the ritualistic behaviors they were compelled to carry out, and that eating the substance led to relief of tension or anxiety. Patients were treated with traditional therapy for OCD, which consisted primarily of psychotherapy, although the effect on pica was variable. Four of the five cases responded to selective serotonin reuptake inhibitors. Neurobiologic testing results (decreased serotonin metabolite concentration in cerebral spinal fluid and frontal lobe hypoactivity on SPECT [single photon emission computed tomography]) for 2 of the patients were more consistent with problems with impulse control, part of the spectrum of disorders in the OCD category. These case reports lend support to the concept that, in some patients, pica might be a manifestation of OCD.
J Am Board Fam Med. 2000;13(5) © 2000 American Board of Family Medicine
Cite this: Pica: Common but Commonly Missed - Medscape - Sep 01, 2000.