Scientists at NIH in Baltimore provide evidence why asthma and autism could be linked to acetaminophen use. In their opening paragraph, the authors state that genes involved in asthma and autism are associated with innate immune pathways. They go on to provide evidence that various immune system abnormalities are documented in autism, including abnormalities in macrophages and mast cells. Along with this, families of children with autism have higher rates of autoimmune conditions. The scientists also refer to the "interesting" statistic that the percentage of children with autism and asthma both increased at the same point in time in 1980, when the CDC recommended stopping the use of aspirin and switching to acetaminophen.
ABSTRACT
Autism and autism spectrum disorders are enigmatic conditions that have their origins in the interaction of genes and environmental factors. In this hypothesis, genes statistically associated with autism are emphasized to be important in inflammation and in innate immune pathways, including pathways for susceptibility to asthma. The role of acetaminophen (paracetamol) in an increased risk for asthma is described, and a possible similar link to an increased risk for autism is suggested.
There is strong epidemiological evidence that acetaminophen use in late pregnancy and/or in the first year of life increases the risk of subsequently acquiring childhood asthma and related allergic disorders. This may be due to direct effects on immunological pathways or secondary effects such as through alterations in blood serotonin, glutathione, or transsulfuration. Fever has been shown to have a modifying effect on behaviors in autism, and acetaminophen is widely used to treat childhood fever as well as symptoms associated with childhood infections and childhood vaccines. Acetaminophen use has been shown to be associated with autism in a preliminary study63.