According to Davis et al (2013)
“Chelation treatment aims to eliminate specific metals from the body. However, empirical evidence has yet to support the hypothesis that the core ASD symptoms are caused by the presence of such metals in the body. Because empirical evidence does not support the hypothesis that the core ASD symptoms are associated with specific levels of metals in the body, the use of chelation to remove metals from the body in order to ameliorate ASD symptoms could be seen as unfounded and illogical.”
and
“Moreover, even if metal poisoning contributed to the ASD symptoms, it would still be unclear whether chelation treatment would have the ability to reverse existing neurological problems caused by such exposure, or whether it would only be able to prevent further damage (i.e., worsening of symptoms). In other words, even if the metal poisoning theories held true, it does not necessarily lead to an expectation that chelation would ameliorate current communication and social skills deficits and behavioral impairments, rather than prevent additional or more extensive impairments.”
There have been various claims for chelation as a treatment for autistic people. For example, Defeat Autism Now! (2005) claimed that
“Many DAN! physicians have reported good improvements with DMSA, although the improvements are sometimes accompanied by gut problems. Reported benefits include rapid progression of language ability, improved social interaction, improved eye contact, and decreased self-stimulatory behaviors (stimming). Children with motor problems have experienced significant improvement in both strength and coordination.”