High BDNF Levels in Autism

Children with autism have increased blood levels of brain-derived neurotrophic factor (BDNF), according to a new meta-analysis. This protein spurs the formation of neuronal connections, or synapses, which may be unusually abundant in individuals with autism. But the study comes with a list of caveats, and it is still unclear what role, if any, BDNF plays in autism, experts say.

Studies probing the link between BDNF and autism have shown mixed results: Some report elevated levels of the protein in people with autism, but others indicate the opposite or no difference relative to controls. Varied methods for collecting and storing samples may contribute to the discrepancies, says Yoke Peng Loh, head of cellular neurobiology at the National Institute of Child Health and Human Development and lead investigator on the new study.

To tease a signal from the noise, Loh and her colleagues compiled results from 19 studies — involving a total of 2,896 children — which measured blood levels of BDNF in children with autism and typical children. “It would be very interesting, we thought, to correlate any changes in blood levels of BDNF and autism,” Loh says.

The analysis revealed that BDNF levels are higher in children with autism than in those without the condition. The results are published in the November issue of JAMA Pediatrics. They jibe with those of two meta-analyses published in August.

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