http://kidshealth.org/parent/emotions/behavior/pica.html
The kinds of items consumed by people suffering from Pica cover a great range including dirt, clay, paint chips, plaster, chalk, cornstarch, laundry starch, baking soda, coffee grounds, cigarette ashes, burnt match heads, cigarette butts, soap, ice, glue, hair, buttons, paper, sand, toothpaste, and even feces.

(Pictured here are the contents of someone’s stomach who suffered from Pica. You can see a great variety of items including metal nails, beads, and stones.)
One can readily assume the kinds of health risks that consuming non-food items can pose. One could accidentally consume lead from paint, or toxins in dirt, even parasites. Now the question that’s on all our minds is what goes through these peoples minds when they continuously feed themselves things they know aren’t intended for consumption?
One example of a patient suffering from pica was a 33-year-old, African American woman admitted to the emergency room with vague abdominal complaints, increasing abdominal girth, weight gain, and episodic nausea and vomiting of several months' duration. Upon further examination it was concluded that these symptoms were a result of her unusual habit of eating dirt. Curiously enough the patient could never attribute her symptoms to this habit, and tried to blame them on other things. When asked about her cravings to eat dirt she recalled first trying dirt as a child, but said that soon after she had stopped because she was afraid of what her parents would do if they found out. Later on when she was 19 years old she had the first of two miscarriages. At this time she described how after the burial service she took a handful of dirt from the grave and ingested it. After the burial of her second stillborn she experienced other bouts of eating dirt as well as throughout other pregnancies. Later on when she had two young children she began instructing her children to gather soil from a neighbors flowerbed for her to eat, (although she never actually told them what the dirt was for).
When asked what about eating dirt appealed to her, she responded with a detailed description of what ingesting dirt was like for her. She said that she enjoyed grabbing a portion of dirt with the plastic pail her children had gathered it with, looking at it, smelling it, and feeling it in her hand, then finally shoving the whole handful into her mouth savoring the “gritty feeling” in her throat.
There are several different proposed causes of Pica. Some are more common than others, however there is no one specific cause because of its vague neurological roots. Some reasons why this disorder is thought to occur includes nutritional deficiencies triggering peculiar cravings, dieting which people eat non nutritional items in attempt to achieve fullness without calories, and also OCD disorder (obsessive compulsive disorder) and schizophrenia.
Pica, as well as many other bizarre mental disorders in modern times has a clear medical cause, but appears to be something out of witchcraft or magic in times of less scientific knowledge. Consider the symptoms of the people thought to be victims of witchcraft during the Salem which trials. A heavily researched theory is that a fungus called ergot, which sometimes infects rye grains, in fact triggered these symptoms of so called “witchcraft”. This fungus produces chemicals, which are very similar to LSD and cause vicious hallucinations and seizures. It’s strange medical phenomenon like this, as well as Pica and many other medical situations that are interpreted very differently depending on the amount of scientific and psychological knowledge available at that time.
Here are my sources...
http://psy.psychiatryonline.org/cgi/content/full/39/5/465
I trust this to be a good source because they are affiliated with many notable organizations such as the Academy Of Psychosomatic Medicine and American Psychiatric Publishing Inc.
http://kidshealth.org/parent/emotions/behavior/pica.html
This seemed like a trustworthy source because of how it is relatively well known it is, and how notable companies endorse it.
http://www.smithsonianmag.com/history-archaeology/brief-salem.html
The Smithsonian Institution is a well-known and reputable source and has been for a long time.