Research that has been done on the causes of pica suggests that the disorder is a specific appetite caused by mineral deficiency in many cases, such as iron deficiency, which sometimes is a result of celiac disease or hookworm infection. Often the substance eaten by someone with pica contains the mineral in which that individual is deficient.
More recently, cases of pica have been tied to the obsessivecompulsive spectrum, and there is a move to consider OCD in the etiology of pica. However, pica is currently recognized as a mental disorder by the widely used Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). Sensory, physiological, cultural and psychosocial perspectives have also been used by some to explain the causation of pica.
It has been proposed that mental-health conditions, such as obsessive-compulsive disorder (OCD) and schizophrenia, can sometimes cause pica.
I might have a mineral deficiency, one that is mainly found in pastries and pies. ;-)