The National Institute of Mental Health decided to give up on its study of a therapy called chelation to treat children with autism.

Whether to start such a study or not has been a subject of controversy for a couple of years but the study never got started.

Chelation therapy consists in the administration of chelating agents to remove heavy metals, such as lead, arsenic or mercury from the body. The therapy has been approved for more than 50 years for the treatment of lead poisoning, but it is not approved for the treatment of autism. Its use as a potential autism treatment is based on the widely spread theory that mercury in vaccines triggers autism. But, according to the US Centers for Disease Control and Prevention, since 2001, with the exception of some influenza vaccines, the mercury-containing preservative has not been used in routinely recommended childhood vaccines. And still, some parents refuse to get their children vaccinated for fear they would develop autism.

The chelation study had reportedly been on hold since 2007 when animal trials linked a specific chelation treatment to brain damage in rats. Some critics called the study “unethical.”

“The Board determined that there was no clear evidence for direct benefit to children that would participate in the chelation trial and that the study presents more than a minimal risk. NIMH has decided that resources are better directed at this time to testing other potential therapies for autism spectrum disorders, and is not pursuing the additional review required to begin the study,” NIMH said in a statement.

Some scientists embraced the decision fearing that such a study would cause more health problems to autism children.

“I think they’re making the right decision not to go forward with the study. Our data raise concerns about administering (the chelation compound) to children who do not have elevated levels of heavy metals,” Barbara Strupp, a professor of psychology and nutritional sciences at Cornell University, who was involved in the rat study.

On the other hand, some parents of autistic children are disappointed in the decision to cancel the study, as they believed in the efficiency of the chelation therapy.

“By discontinuing this study, the NIMH will not prove the effectiveness of chelation therapy one way or another. Instead, they have merely left parents with more unanswered questions,” Rebecca Estepp, national manager of Talk About Curing Autism, a support group for families with autistic children. She is the mother of a 10-year-old autistic boy.

Estepp also added that she knows of thousands of children who have improved and even had their autism symptoms disappear following chelation therapy.

Autism is a spectrum of different disorders ranging in severity and in symptoms from the mild Asperger’s syndrome to more severe autism. The disease, characterized by poor social interactions, impaired communication and repetitive behavior, affects as many as 1 in every 150 kids in the U.S., according the Centers for Disease Control and Prevention. Studies have shown that males are four times more likely to have autism than females.