Mercury and autism link strengthened

According to researchers a family history of mercury poisoning could be a significant risk factor for developing autism.

The researchers from Swinburne University in Melbourne surveyed 522 Australian survivors of Pink disease - a form of mercury poisoning common in the early 20th century - found one in 25 of their 398 grandchildren aged six to 12 had an autism spectrum disorder. This prevalence is six times higher than the one-in-160 diagnosed in the general population. Author Associate Professor David Austin said, “We asked the pink disease survivors to report any health conditions that their children or grandchildren had been diagnosed with… The survey included questions about Down syndrome, fragile X syndrome, attention deficit hyperactivity disorder (ADHD), epilepsy and autism.” The prevalence rate of most disorders was comparable to general population figures, however, the rate for autism was extremely high.

Pink disease affected 1 in 500 young children with a hyper-sensitivity to mercury, it caused a range of severe symptoms including loss of speech, loss of interest in usual activities, hypersensitivity to light, pain and, in up to 20 per cent of cases, death. When mercury was identified as the culprit and removed as an ingredient in teething powders in the 1950s, the disease was essentially wiped out.

The study, published this week in the Journal of Toxicology and Environmental Health, found the grandchildren did not have elevated rates of other conditions such as epilepsy, Down syndrome or attention deficit hyperactivity disorder. Authors write that this study added to mounting evidence of a link between genetics, mercury sensitivity and autism-spectrum disorders. They said the research also strongly suggested autism was caused by combined genetic and environmental factors.

Since autism was first recognized as a disorder, scientists have been trying to identify its cause. There have been two warring camps; one that attributes autism to genetics and the other which claims it is caused by an environmental trigger…This study suggests that it may actually be a combination of the two. That is, genetic susceptibility to a trigger (mercury) and then exposure to that trigger. In this sense, it is like a peanut allergy. For most of us peanuts are completely harmless but, for those who are allergic, there can be serious consequences if there is exposure,” Austin said.

Researchers at Swinburne Autism Bio-Research Initiative (SABRI) are now extending their research by examining cellular and genetic characteristics of Pink Disease survivors and people with autism. The results are expected to be released in 2012. In the meantime, Austin suggests those with a suspected family history of pink disease to minimize their exposure to mercury. This is particularly important for young children and women who are pregnant or breastfeeding. “This can be done by observing the recommendations of Food Standards Australia regarding seafood consumption, opting for non-amalgam dental fillings and requesting preservative-free vaccines from your doctor,” Austin said.

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