The theory that more severe symptoms of autism spectrum disorder (ASD) may be due to increased levels of toxic metals, and as such excretion via pharmaceutical chelating agents could lead to symptom improvement, is highly controversial. Although between 6–11% of families of children with ASD in various English-speaking countries have reported trying chelation therapy, research on its safety and efficacy in this population is scarce.

A new review in the Cochrane Library found only one randomized double-blind study to evaluate the efficacy of repeated doses of oral dimercaptosuccinic acid (DMSA) in decreasing core features of ASD in children who have previously received a three-day course of oral DMSA and are known to be high excreters of heavy metals. The study was separated into two phases, with 65 children completing phase one and 41 completing phase two. In phase one, participants were randomly assigned to receive seven days of glutathione lotion (experimental group) or placebo lotion (control group) followed by oral DMSA 10mg/kg three times per day for three days for all participants to test topical glutathione’s potential role in increasing the efficacy of oral DMSA. In the second phase, a subset of participants identified as high heavy metal excreters were randomly assigned to three days of oral DMSA or placebo, followed by 11 days off, with the cycle repeated up to six times. All children (mean age 6.3 years) had a confirmed diagnosis of ASD by a psychiatrist, psychologist, or developmental pediatrician.

The reviewers found no high-quality evidence to suggest that chelation therapy is an effective treatment for improving ASD symptoms. The study had a high or unclear risk of bias and the quality of evidence was poor. Based on the potential harm of chelation therapy and no proven benefits for children with ASD, it should not be recommended as an alternative treatment for ASD.