Abstract
Gluten free/Casein free (GFCF) diets are one of the most common types of Complementary and Alternative Medicines (CAM) used in Autism Spectrum Disorders (ASD) despite little evidence to support positive effects. There has been no theory driven literature that has investigated parent's reasons for their use. The Theory of Planned Behaviour (TPB) was used to examine parent's intentions to use GFCF diets for their child with an ASD. Treatment and causal beliefs were also examined. Parents (n = 33, children aged 3-17 years) were influenced by anticipated regret, positive outcomes and attitude. Future interventions should provide information to parents and health professionals about the possible causes of ASD and therapy options which are in line with current recommendations.