Definition: 'pica is a pattern of eating non-food materials, such as dirt or paper'. So goes the description provided by PubMed Health. Indeed, pica is apparently not such an uncommon issue among young children and women in particular, as partners of pregnant women the world over think back to late night shopping trips for such 'inedibles' as pickled onions or marmite (just kidding).
Seriously though, pica during pregnancy can be a very real occurrence. Likewise, many parents will have probably seen something approximating pica at some point in their child's early years; whether it be that lovely wallpaper border you bought for the little darlings room (that wasn't cheap!) or that elusive missing piece of the jigsaw puzzle (which re-emerges a few days later from a galaxy far, far away in a nappy or toilet basin). I think Piaget called it the 'sensorimotor stage'.
Pica in cases of autism and related conditions has been discussed before on this blog in one of my posts on zinc. Indeed the link with zinc in cases of autism (as in, some suggestion of deficiency in quite a few cases) shares some interesting comparisons with regards to zinc deficiency and cases of pica slightly outside of autism as per studies like this one and this one. Zinc is not the only element being linked to pica as per other research on iron deficiency suggestive of a link.
Given this and other data with regards to what happens to pica when such nutritional deficiencies are remedied, one gets the impression that there may be some kind of nutritional search potentially on-going in cases of pica rather than just mindless eating. But that might not be the whole story as per my recent post touching on gustational sensitivity and autism.
Where pica is present, there are a number of potentially important issues that might need to be looked at.
- Bezoars and other foreign bodies are always going to be a concern depending on what is being eaten and its size. Various case studies litter the research environment with regards to intestinal obstructions in individual cases of autism as per these studies by Serour and colleagues* and Conyers & Efron**. I'm not quite sure about some of the suggestions put forward to stop pica behaviours such as the "minimally obtrusive, secure mask" suggested by Taylor & Walker*** and even less so for the use of aromatic ammonia examined by Rojahn and colleagues****. That's not to say however that behavioural 'training' might not have some effect on pica as per teaching about edible and non-edible items reported by Kern and colleagues*****.
- Given the material and objects that pica may include (e.g. soil) there is always a risk of either some kind of poisoning or infestation as a result. So blood levels of things like lead have been touched upon in the research literature (here) and indeed quite recently suggested to be something to watch where pica may be an issue****** (full-text). I assume other metals might also require similar monitoring. Insofar as infestation, and in particular, parasitic infestation, the research literature with autism in mind is still sparse. Certainly parasites such as Giardia lamblia causing giardiasis are known to be associated with pica and there may be others too.
- A final issue to bear in mind relates to the potential functional effect of long-term pica on teeth and dental health. I appreciate that dental health can be a tricky issue in relation to autism for lots of other different reasons not least difficulties in installing a consistent brushing routine and the effects of potential comorbidities such as bruxism (teeth grinding). If one considers that pica may include objects which are not necessarily all soft and fluffy such as stones/rocks, or may have the propensity to lead to frequent vomiting, you could see how teeth and oral health might also suffer.
Appreciating that pica is not a part of every autistic persons behaviour, there are perhaps a few things that can be learned from pica when present. Regular readers of this blog will (hopefully) know that I am a bit of a believer in endophenotypes when it comes to autism - so subgroups are potentially apparent in the larger constellation that is know as 'autism'. The tie-up between pica and nutritional deficiencies is potentially an important clue to one of those phenotypes and dare I suggest it, a possible marker waiting in the wings?
* Serour F. et al. Intestinal obstruction in an autistic adolescent. Pediatric Emergency Care. 2008; 24: 688-690.
** Conyers R. & Efron D. Agitation and weight loss in an autistic boy. Journal of Pediatrics & Child Health. 2007; 43: 186-187
*** Taylor MB. & Walker RA. A minimally obtrusive, secure mask for prevention of access to the mouth. Clinical Rehabilition. 1997; 11: 77-79
**** Rojahn J. et al. Suppression of pica by water mist and aromatic ammonia. A comparative analysis. Behaviour Modification. 1987; 11: 65-74.
***** Kern L. et al. Reducing pica by teaching children to exchange inedible items for edibles. Behaviour Modification. 2006; 30: 135-158
****** Clark B. et al. Is lead a concern in Canadian autistic children? Pediatrics & Child Health. 2010; 15: 17-22