A new paper from the MIND Institute and UC Davis links pre-pregnancy obesity (>198 lbs) and excessive weight gain during pregnancy (>40 lbs) with increased risk for autism spectrum disorder (ASD) or developmental delay in the offspring. In the population studied, >20% of the mothers with an ASD child were obese compared with 14% of mothers without an ASD child, so this is not a huge effect but is statistically significant. Among other problems, obesity is associated with an inflammatory state, which includes elevated levels of the cytokine IL-6, which our animal studies have shown is critical for mediating the changes in fetal brain development that lead to autism- and schizophrenia-like behaviors in the offspring (see also our paper on maternal IL-6 effects on the placenta). These issues are discussed in more detail in my book. The most interesting point about this new paper is that it suggests a link between the rising incidence of obesity and the rising incidence of ASD. Could they be related? Is stress also increasing during pregnancy? IL-6 rises during stress, and maternal stress increases the risk for schizophrenia in the offspring.
Another interesting aspect of this story is the genetic contribution to obesity. Along with the environmental changes that undoubtedly contribute to the obesity epidemic (easy access to high calorie foods and sedentary lifestyles), twin studies indicate a high heritability for this metabolic condition. A recent paper from the Children’s Hospital of Philadelphia identified several variations in the genome (known as copy number variations, CNVs) are associated with childhood obesity. Most interesting to me was that one of these variations occurs in FOXP2, a gene identified as being important for speech and language (covered in detail in my book). Although this CNV finding applies to only a tiny number of children, it hints at another possible connection between ASD and obesity.