Might mitochondria—the little packets inside cells that make energy for both brain and body—play a role in autism?

Perhaps in some cases of the disorder, two researchers believe. They are Daniel Rossignol, M.D., a primary care physician affiliated with the International Child Development Resource Center in Melbourne, Fla., and Richard Frye, M.D., Ph.D., of the University of Texas Health Science Center at Houston.

Mitochondria are best known for producing energy for the cell from oxygen and food. Because of mitochondria's role in energy production, children with mitochondrial disease have some level of dysfunction in high-energy organs such as the brain. Children with mitochondrial disease can have either normal intelligence, mental retardation, or developmental delay.

On the basis of a review of 65 studies, Rossignol and Frye concluded in a report in the January 25 Molecular Psychiatry that 1 in 20 children with autism has mitochondrial disease, which is much higher than the incidence in the general population, which is about 1 in 10,000 children.

Moreover, they compared children with both autism and mitochondrial disease with children who had autism without mitochondrial disease and with nonautistic children with mitochondrial disease and uncovered some interesting findings.

For example, children who had both autism and mitochondrial disease were significantly more likely than children with autism but no mitochondrial disease to develop normally early in life and then to lose some previously acquired skills.

Furthermore, children who had both autism and mitochondrial disease were significantly more likely to experience seizures and gastrointestinal abnormalities than were children with autism but no mitochondrial disease and children with mitochondrial disease but no autism.

"Overall, this evidence supports the notion that mitochondrial dysfunction is associated with autism spectrum disorders," the researchers concluded, but they added that more studies are required before the role that mitochondrial dysfunction plays in autism can be defined.

But if there is a causal effect, then the question is: Could treating mitochondrial disease improve the health of children who have both autism and mitochondrial disease?

Rossignol believes that to be the case, he told Psychiatric News. "[Some] studies reported improvements with antioxidants such as carnitine, coenzyme Q10, and B vitamins. We also see improvements in children with autism and mitochondrial disease when we use these in clinical practice."

The research was funded by the Autism Research Institute and the Jane Botsford Johnson Foundation. Both Rossignol and Frye noted a possible conflict of interest in their paper. Rossignol has two children with autism and treats autistic children with both standard and integrative treatments. Frye provides expert testimony for children with mitochondrial disorders who may have been injured from vaccines. ("In our review," Rossignol told Psychiatric News, "there were several published cases of regression into autism and mitochondrial disorder that were associated temporally with vaccination, often in association with fever. However, there is very little published research on this subject.")

"Numerous studies have now documented the presence of mitochondrial dysfunction in a subset of patients with autism spectrum disorders," David Fassler, M.D., a child and adolescent psychiatrist and a clinical professor of psychiatry at the University of Vermont, told Psychiatric News. "The results of the current meta-analysis are consistent with such previous reports … . The authors readily acknowledge the limitations of their study, including reliance on small sample sizes and possible referral and/or publication bias. However, I would certainly concur with their conclusion that this is a promising area for future research. Hopefully, such efforts will ultimately enhance our ability to diagnose and treat children, adolescents, and adults with autism spectrum disorders."

An abstract of "Mitochondrial Dysfunction in Autism Spectrum Disorders: A Systematic Review and Meta-analysis" is posted at <www.nature.com/mp/journal/vaop/ncurrent/full/mp2010136a.html>.