Autism seems to be increasing worldwide, if not in London

EDITOR – As described by others, in some areas of the world there has
been an increase in the number of children reported to have autism.(1 2)
The extent to which this increase is due to improved reporting, changes in
diagnostic patterns, a true increase in the incidence/prevalence, or a
combination is unknown. Autism is most likely of mutlifactorial etiology
with many causal factors, both genetic and environmental. We would like
to pose another factor that may be a cause of autism – iodine deficiency.

In a number of countries with reported increases in autism there has
been a concomitant increase in the prevalence of iodine deficiency.(3 4 5)
Another line of evidence is the effect of iodine deficiency on brain
development and the findings in some children with autism. Iodine
deficiency during the prenatal period has been associated with a number of
adverse effects on the brain resulting in a continuum of effects from mild
to severe depending on the degree of iodine deficiency, from lowered IQ to
severe mental retardation, i.e., cretinism. The mechanism of iodine
deficiency is that insufficient levels of iodine lead to an imbalance in
thyroid hormone metabolism with a decrease in circulating thyroxin (T4) in
both the pregnant mother and the fetus. This results in irreversible
changes in brain architecture such as less dense neural connections.(6) It
has been reported that some children with autism have “underconnectivity”
in certain regions of the brain.(7)

In conclusion, there are similarities between the effects of iodine
deficiency on the brain of the developing fetus and the pattern of brain
dysfunction seen in some children with autism. We believe that there is
evidence to support the theory that some of the reported increase in
reported autism might be attributed to iodine deficiency, and that this
warrants further investigation

Kevin M. Sullivan, Associate Professor

cdckms@sph.emory.edu

Glen F. Maberly, Professor

Rollins School of Public Health of Emory University, Atlanta GA, USA

Competing interests: None declared.

1 Prior M. Is there an increase in the prevalence of autism spectrum
disorders? J Paediatr Child Health 2003;39:81-82.

2 Yazbak FE. Autism seems to be increasing worldwide, if not in
London. BMJ 2004;328:227.

3 Kibirige MS, Hutchison S, Owen CJ, Delves HT. Prevalence of
maternal dietary iodine insufficiency in the north east of England:
implications for the fetus. Arch Dis Child Fetal Neonatal Ed 2004
Sep;89(5):F436-9.

4 McDonnell CM, Harris M, Zacharin MR. Iodine deficiency and goitre
in schoolchildren in Melbourne, 2001. Med J Aust 2003;178(4):159-162.

5 Skeaff SA, Thomson CD, Gibson RS. Iodine Deficiency Disorders
(IDD) in the New Zealand population: another example of an outmoded IDD
control programme. Asia Pac J Clin Nutr 2003;12 Suppl:S15.

6 Stanbury JD, Ed. The Damaged Brain of Iodine Deficiency. Cognizant
Communication Corp, New York. 1994.

7 Just MA, Cherkassky VL, Keller TA, Minshew NJ. Cortical activation
and synchronization during sentence comprehension in high-functioning
autism: evidence of underconnectivity. Brain 2004:127(Pt 8):1811-1821.

Competing interests:
None declared