ABSTRACT
This chapter discusses the research involving gastrointestinal problems and autism spectrum disorders, evaluate theories concerning how they are related, and discuss implications for practice. The Opioid Excess Theory has been refined and it has been hypothesised that the opioid peptides derived from gluten and casein are able to enter the bloodstream through the lumen of the intestine due to two biological deficits, inadequate production of enzymes to digest gluten and casein and increased gut permeability. The hypothesis that the measles, mumps and rubella (MMR) vaccine is related to autism has been extensively evaluated from a range of perspectives. One approach has been the use of ecological studies that have studied the relationship between the MMR vaccine and autism. While constipation can result from numerous factors, in this case it was attributed to inadequate intake of fibre and fluids, and possibly stool withholding.
