What sorts of things are your children ingesting? Any other diagnoses like ADHD or autism? My son was never diagnosed with PICA but one of the odd behaviors I noticed years ago was how he would gnaw on plastic (bottle caps, pencil caps, etc.) and chewing them like they were gum. It was extreme . . . he looked and acted like a drug addict looking for a fix . . . it was obvious he was "craving" something and looking to feed some underlying need. When we started biomed therapy to treat his ADHD, he stopped the behavior as soon as he started vitamin supplementation. Even now, if he starts the behavior again, I know it's time to have him evaluated again and sure enough, the behavior stops once his vitamin regimen is tweaked and corrected to accommodate his growing needs.
at 7:35 AM on Oct. 1, 2008