A recent paper from the MIND Institute , published in the Journal of the American Medical Association (JAMA) entitled Mitochondrial Dysfunction in Autism caused a bit of a stir. One which is far beyond what is supported by the paper’s conclusions or data, I will add.
The study is very small: 10 autistic children and 10 controls. The authors used a very nonstandard methodology. Perhaps the best summary of this study so far can be found on the Simons Foundation blog SFARI ( Defects in mitochondria linked to autism ). Deborah Rudacille discusses the methodology and brings in quotes from the study’s lead author ( Cecilia Giulivi ) as well as established experts in the field of mitochondrial disease and autism such as Jay Gargas .
Before I get too far ahead of myself, here is the abstract:
Context Impaired mitochondrial function may influence processes highly dependent on energy, such as neurodevelopment, and contribute to autism. No studies have evaluated mitochondrial dysfunction and mitochondrial DNA (mtDNA) abnormalities in a well-defined population of children with autism.
As the abstract states, the MIND Institute study methodology involved: “Mitochondrial dysfunction and mtDNA abnormalities were evaluated in lymphocytes from 10 children with autism and 10 controls”. Lymphocytes (a type of white blood cell). Children were concecutively recruited and genetically unrelated. Mitochondrial function was tested first, and given the results seen, children were brought back for a second blood draw where mitochondrial DNA (mDNA) and nuclear DNA (nDNA) were examined.
As shown in the figure below, they found that the autistic children had different mitochondrial activity levels than their controls. Note that “low” activity is not referenced to any standardized norms, but to the 10 control children.
They also performed genetic testing. Table 3 from the paper is reproduced below:
They show that, by their methodology, 7 of their 10 autistic kids have some form of genetic signature for mitochondrial dysfunction. 2 of 10 of their controls meet their criteria as well.
The Simons blog quotes the study author, Prof. Giulivi on this choice:
“Lymphocytes do not rely as heavily on mitochondria as the brain does,” she says, “so if this is happening in cells that don’t use mitochondria as much, it’s likely to be happening in cells that rely more heavily on mitochondria, like neurons.”
They also quote Dr. Fernando Scaglia , of the Baylor Clinic:
However, the unconventional decision to use lymphocytes should have been validated, says Fernando Scaglia, associate professor of molecular and human genetics at Baylor College of Medicine in Houston. “I’m not saying that studies done in lymphocytes are useless,” says Scaglia, an expert in inherited metabolic disease. “But they should be validated in other tissue.”
and Prof. Gargas of the University of California at Irvine:
“Lymphocytes are fine to study chromosomal DNA, but they are a horrible source for studying mitochondrial DNA,” he says.
In the end, if we stick to the idea that this is a very preliminary report and relies on a new unproven methodology at that, we can consider the study as posing interesting questions. Is mitochondrial dysfunction more prevalent in autistics than the general population? Are there ways to test this in a faster, less intrusive manner than is often used? If we take this study in context, there may be some value. Unfortunately as Seth Mnookin has already pointed out , this study has already been used to promote ideas that are clearly outside of the study and conclusions. This is the unfortunate world of autism research: it is hard for people to push the boundaries and risk being wrong. Not because it may cause the researchers some embarrassment, but because there are a multitude of people waiting to misuse information and mislead.