The British Journal of Developmental Disabilities
Vol. 45, Part 2, JULY 1999, No. 89
PICA AND TRACE METAL DEFICIENCIES IN ADULTS
WITH DEVELOPMENTAL DISABILITIES
Irene Swift, Dana Paquette, Kristina Davison and Haider Saeed
Introduction when pica is defined as the compulsive eat-
ing of both non-food and food items
Pica is an eating disorder defined as the (Danford and Huber, 1982).
frequent consumption of non-food items This disorder can lead to serious health
and the excessive, compulsive eating of problems, including intestinal obstruction
food and food-related substances (Danford by ingested foreign bodies, vomiting and
and Huber, 1982). It is more common in spe- lead intoxication (Danford and Huber, 1982).
cific populations such as pregnant women, There is thus considerable interest in dis-
children aged 1 to 6 years and people with covering the aetiology of this eating disorder
developmental disabilities (Feldman, 1986). as an aid in eliciting treatment or even cure.
Among people with developmental dis- Among individuals with developmental
abilities, pica is the most frequently ob- disabilities, many causes of pica have been
served eating disorder (Danford and Huber, proposed. The inability to distinguish non-
1982). Studies conducted in institutional set- food items from food items is one example
tings report a prevalence of 9% to 16% when (Bicknell, 1975). Pica has also been viewed as
using a definition of pica restricted to the a developmental mouthing difficulty re-
ingestion of non-food items (Lofts et al., lated to the intellectual disability itself, thus
1990; McAlpine and Singh, 1986; Tewari et requiring behaviour modification treatment
al., 1995; Wakham et al., 1992). A prevalence (Ausman et al., 1974). These hypotheses can
of 25% has been found in this population be supported by findings of an increase in
*Irene Swift, M.B., B.S.
Assistant Professor, Department of Family Medicine, Queen’s University at Kingston
Primary Care Physician, Rideau Regional Centre, PO Box 2000, Smith Falls, Ontario, Canada
Tel: 001 613 284 0123 Fax: 001 613 284 0669
Dana Paquette, M.Sc.
At time of study: Research Associate, Developmental Consulting Program, Queen’s Univer-
sity at Kingston
Present Position: Analyst, Cancer Bureau, Laboratory Centre for Disease Control, Health
Kristina Davison, B.Sc.
Medical Student, School of Medicine, Queen’s University at Kingston
Haider Saeed, B.A.
Educational Associate, Developmental Consulting Program, Queen’s University at Kingston
* For Correspondence
the occurrence of pica with the severity of the need for further research. However, the
mental retardation (Danford and Huber, interpretability of the results is limited due
1982; McAlpine and Singh, 1986; Tewari et to the small control groups. In addition,
al., 1995). Researchers have also proposed both studies neglected to adjust for other
that pica is related to certain psychiatric dis- variables found or thought to be associated
orders, such as depression, in adults with with pica, such as sex, level of mental retar-
developmental disabilities (Jawed et al., dation, age, autism, depression or schizo-
1993) and autism (Kinnell, 1985). Other phrenia (Danford and Huber, 1982; Jawed et
causes suggested in the literature include al., 1993; McAlpine and Singh, 1986;
boredom, hunger and addiction McLoughlin, 1987; Tewari et al., 1995).
(McLaughlin, 1987; Tewari et al., 1995) The aim of the present study was to de-
Among non-disabled groups, attention termine the prevalence of pica in adults
has focused on trace metal deficiencies as a with developmental disabilities living in an
possible cause of pica. It is proposed that institutional setting, and to describe the
pica is a result of an instinctive ability to rec- types of pica detected classified according
ognise a deficiency and to know which sub- to the various items ingested. In addition,
stances contain that vital nutrient (Feldman, this study examined the association between
1986; McLaughlin, 1987). The presence of trace metal levels and pica in individuals
pica among non-disabled groups has been with developmental disabilities. A case-con-
correlated with low serum iron levels trol design was used to explore the associa-
(Bothwell, 1972; Geissler et al., 1998), low se- tion between pica and levels of iron, zinc,
rum and hair zinc levels (Chen et al., 1985) copper and magnesium while adjusting for
and elevated serum copper levels (Cheek et associated variables.
Few studies have explored this “nutri-
tional hypothesis” among adults with de- Method
velopmental disabilities. Danford et al.
(1982) evaluated 60 adults with pica and 6 Rideau Regional Centre (RRC) is a pro-
without for iron, zinc, copper and magne- vincial residential facility in eastern Ontario
sium levels. Plasma zinc and iron were sig- for adults with developmental disabilities.
nificantly reduced in those with pica, At the time of the study, RRC served 689 in-
plasma copper was slightly but not signifi- dividuals. To determine the prevalence of
cantly elevated in those with pica, and pica within the facility, all residents were
plasma magnesium was in the low normal assessed for the occurrence of pica behav-
range and did not differ significantly be- iours. A variant of Danford and Huber’s
tween the two groups. Lofts et al. (1990) ana- (1982) definition of pica was used to identify
lysed the serum zinc levels of 128 residents the case group: the frequent consumption
with pica and 30 frequency-matched con- of non-food and food-related substances. A
trols. The mean serum zinc level was signifi- survey questionnaire, distributed to the staff
cantly lower in the group with pica, of all living areas, was used to identify resi-
supporting the notion that trace metal defi- dents with pica behaviour. The question-
ciencies may play a role in the aetiology of naire asked for the name of each resident
this disorder among persons with develop- with pica along with the names of the spe-
mental disabilities. cific items they had ingested. These data
These two studies (Danford et al., 1982; were then confirmed by verbally question-
Lofts et al., 1990) were useful in establishing ing the ward staff, consulting the “high risk
board” on every area and checking the ence with MDS Laboratories). Levels were
medical problem list of each resident’s file. considered abnormal (low or high) if they
These steps identified fifteen additional resi- fell outside of the MDS reference ranges.
dents with pica who were missed by the The reference range was dependent on the
original survey questionnaire. age and sex of the participant for iron, and
Residents with pica were categorised was sex dependent for copper (9.0 - 23.0
into single, multiple and nondiscriminating umol/l for males, 11.0 - 30.0 umol/l for fe-
pica according to the types of substances in- males). The reference range for magnesium
gested. Those who consumed only one type was 0.70 - 1.00 mmol/l, and 11.5 - 23.0 umol/l
of item were categorised as single pica, those for zinc regardless of the age or sex of the
who consumed a combination of two to participant.
five items were categorised as multiple pica, Information on level of mental retarda-
and those who consumed six or more items tion, age, sex, autism and psychiatric disor-
were described as nondiscriminating, as per ders such as depression and schizophrenia
Danford and Huber’s (1982) categorisation was collected from the charts of both cases
of pica. Residents with pica were also classi- and controls.
fied into: non-food pica (e.g. string, ciga- Statistical analysis was performed using
rettes, paper); food-related pica (e.g. coffee the Statistical Package for Social Sciences.
grounds, food from garbage); and com- Chi-square and Fisher’s Exact Test were
bined non-food and food-related pica. used to examine associations between pica
In total, 152 residents (22.1%) of RRC and trace metals, age, sex, level of mental re-
were found to have pica behaviour. In order tardation, and psychiatric disorders. Logistic
to measure plasma minerals (iron, zinc, cop- regression was conducted to further exam-
per and magnesium), blood samples were ine the relationship between pica and any
collected from those residents engaging in variable associated with pica at p<0.1.
pica and an equal number of non-pica con-
trols. These samples were collected at the
same time as blood drawn for routine an-
nual studies, which includes a complete Results
blood count and liver function tests. The
control group consisted of the first 152 resi- Among the 152 residents engaging in
dents from the remaining non-pica popula- pica behaviour, the male to female ratio was
tion of the facility to have annual 1.5 : 1. Most (84.2%) had a profound level of
bloodwork completed. mental retardation. The ages ranged from 24
Blood was drawn into Vacutainer tubes to 77 years with a mean age of 45.1 years
by the laboratory technologist, who used a (SD = 9.4). Of those with pica, 89.2% en-
stainless steel needle in the early morning. gaged in non-food pica, 4.7% in food-related
The glassware had previously been spe- pica, and 6.1% in a combined non-food and
cially washed to remove any residual trace food-related pica. Almost a third (28.1%) of
metals from the production process. Serum those with pica had a preference for a single
was sent to a private laboratory (MDS) for item, 53.4% had multiple pica and 18.5%
analysis. Iron was analysed using the Auto- were nondiscriminating in their preference.
mated Chemiluminescence System method, The items consumed are indicated in TA-
copper and zinc with the atomic absorption BLE I. The most frequently consumed items
method, and magnesium using the were strings and thread (30.9%), followed
colorimetric method (personal correspond- by cigarettes and cigarette butts (20.4%),
faeces and vomit (20.4%), and cloth and rags with low serum zinc had 6.25 times the
(18.4%). odds of having pica.
Comparisons were made between the
152 cases and 152 controls on trace metals,
age, sex, level of mental retardation, autism, Discussion
depression and schizophrenia. As indicated
in TABLE II, significantly more individuals This study revealed pica to be of notable
with pica had a profound level of mental proportion among people with develop-
retardation (p<0.001), low levels of zinc mental disabilities living in an institutional
(p<0.001) and low levels of iron (p<0.001). setting. Almost a quarter (22.1%) of the 689
Logistic regression was conducted us- residents of Rideau Regional Centre en-
ing pica as the outcome, and iron, zinc, and gaged in pica behaviour. The prevalence re-
level of mental retardation as the independ- sembles that reported by Danford and
ent variables (see TABLE III). The results in- Huber (1982), who found 25.8% with pica.
dicated that iron, zinc and level of mental Further study is needed to determine the
retardation were all independently associ- prevalence of pica among persons with de-
ated with the presence of pica. According to velopmental disabilities living in commu-
the odds ratios, an individual with a level of nity settings. Environment may have an
mental retardation in the profound range impact on the prevalence of pica depend-
had 3.9 times the odds of having pica. Par- ing on the structured activities available, ac-
ticipants with low serum iron had 5.43 cessibility of pica objects, and the amount of
times the odds of having pica, and those supervision (Tewari et al., 1995; McAlpine
Number of residents who consumed the following items (n = 152)
Items consumed* n %
String, thread 47 30.9
Cigarettes, cigarette butts 31 20.4
Faeces, vomit 31 20.4
Cloth, rags 28 18.4
Grass, leaves 23 15.1
Paper 17 11.2
Dirt, soil 14 9.2
Food from floor or garbage 12 7.9
Shampoo, soap, toiletries 7 4.6
Plastic, plastic wrap 6 3.9
Hair, fingernails 5 3.3
Toilet water 5 3.3
Stones, rocks 5 3.3
Crayons 4 2.6
Coffee, coffee grounds 2 1.3
Other (shoes, paper clips, peach pits, etc.) 40 31.3
*Not mutually exclusive
and Singh, 1986). Such studies will become and Huber, 1982; McAlpine and Singh,
increasingly important as people with 1986; Tewari et al., 1995). A few exotic pica
developmental disabilities continue to items were also found, such as Christmas
move from institutional to community ornaments and colostomy bags. Important
settings. to note is that almost a third of those with
Many different types of pica were iden- pica behaviour had a preference for a single
tified in this survey. As found in previous item. This replicates the findings of Danford
studies, ingested items included paper, and Huber (1982) who reported that indi-
cloth, cigarettes, thread and grass (Danford viduals with pica were generally specific
Comparison of residents with and without pica (%)
Without pica Pica P-value*
Variable (n = 152) (n = 152)
21 - 30 4.7 3.3 0.789
31 - 40 29.3 28.3
41 - 50 40.0 44.1
51 - 60 19.3 17.8
=>61 6.7 6.6
Male 63.3 59.9 0.383
Profound level of Mental Retardation 53.3 84.2 0.000
Schizophrenia 1.4 2.9 0.441
Autism 5.6 8.8 0.312
Depression 0.7 0 1.000
Copper (High) 2.7 2.0 0.565
Iron (Low) 4.7 27.0 0.000
Magnesium (Low) 0 1.4 0.244
Zinc (Low) 3.3 23.8 0.000
*Chi-square or Fisher’s exact test
Summary of regression analysis with pica as outcome
Variable ß P-value* OR (95% CI)
Level of Mental Retardation 1.362 0.0000 3.90 (2.17 - 7.01)
Iron 1.693 0.0002 5.43 (2.23 - 13.22)
Zinc 1.832 0.0004 6.25 (2.27 - 17.19)
about the choice of items ingested. These by Lofts et al. (1990), who found that zinc
findings run contrary to the belief that the supplementation reduced pica behaviour.
occurrence of pica among people with de- Randomised clinical trials of the effects of
velopmental disabilities is related to the in- zinc or iron supplementation on pica be-
ability to discriminate between edible and haviour are needed to better understand the
nonedible items (Bicknell, 1975). direction of this relationship among people
In this study, we found no association with developmental disabilities. Also, the
between pica and age, sex, nor with the spe- negative side effects of excessive supplemen-
cific psychiatric disorders of autism, depres- tation treatment must be considered. Some
sion or schizophrenia. Pica was significantly studies have shown that large doses of zinc
associated with level of mental retardation. may result in copper deficiency, macrocytic
Eighty-four percent of those with pica had a anaemia and neutropenia (Lofts et al., 1990).
profound level of mental retardation as When considering a treatment for pica,
compared to 53.3% in the non-pica group. it is important to take into account a
Caregivers and health care practitioners car- number of variables, including biological,
ing for people with a level of mental retarda- environmental and behavioural factors. An-
tion in the profound range should be on the ecdotal data from the residential facility sup-
alert for the presence of this disorder. Previ- port this notion. One case of pica was said
ous studies have found pica to be an under- to have resolved after the removal of envi-
reported problem that can have serious ronmental stressors, while a second case
medical complications (Danford and Huber, was resolved following iron supplementa-
1982). tion. Pica is a complex disorder that likely
Pica among persons with developmen- has multiple aetiologies, and the analysis
tal disabilities has been commonly viewed and treatment of this disorder should reflect
as simply the result of the intellectual dis- this complexity. The current study provides
ability. The current study, however, estab- evidence of an association between trace
lishes a link between pica and low levels of metal deficiencies and the occurrence of
serum zinc and iron, independent of the pica among adults with developmental dis-
individual’s level of mental retardation. abilities.
These results suggest that trace metal defi-
ciencies may play a role in the aetiology of
pica among some individuals with develop- Summary
mental disabilities. However, more research
is needed into the direction of the relation- A survey of residents with pica was con-
ship, since causation cannot be implied due ducted in a provincial facility for adults
to the design of the study. It is possible that with developmental disabilities. Of the total
the pica itself is causing gastrointestinal population of 689 residents, 152 (22.1%) en-
malabsorption of nutrients, leading second- gaged in pica behaviour. Almost a third of
arily to deficiencies. Another possibility is the residents with pica had a preference for
that nutritional deficiencies are induced by a single item. An equal number of residents
pica through the replacement of normal without pica was chosen as a comparison
food groups with the non-nutritive item group. An analysis of the study population
(Danford et al., 1982). of 304 residents revealed no association be-
Supporting the hypothesis of trace metal tween pica and age, sex, autism, depression
deficiencies as a cause of pica among adults or schizophrenia. Pica was however signifi-
with developmental disabilities is a study cantly associated with a profound level of
mental retardation and low levels of serum Jawed, S. H., Vallepur, H. R., Krishnan, H. R.,
zinc and iron. The clinical and research im- Prasher, V. P. and Corbett, J. A. (1993).
Worsening of pica as a symptom of depressive
plications of the results are discussed.
illness in a person with severe mental
handicap. British Journal of Psychiatry, 162, 835-
Acknowledgement Kinnell, H. G. (1985). Pica as a feature of autism.
British Journal of Psychiatry, 147, 80-82.
The authors thank Susan Leslie for her Lofts, R. H., Schroeder, S. R. and Maier, R. H.
technical support. (1990). Effects of serum zinc supplementation
on pica behavior of persons with mental
retardation. American Journal on Mental
Retardation, 95, 103-109.
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