Connections Between the Brain and Heart in Autism

Recently, two interesting research summary articles published online at Spectrum indicate that children and adults with autism display characteristic differences in heart rates, suggesting the autonomic nervous systems of their brains also function differently. In “Nerves that control heart rate may contribute to autism,” published February 19, 2019, Nicholette Zeliadt describes contrasts between heart rate changes in typical children and those with autism. [To read this article, please click here.]

Referencing “Developmental trajectories of autonomic functioning in autism from birth to early childhood,” published March 2019, in Biological Psychology, this Spectrum article explains research done at Brown University in the United States. [To read this research article, please click here.] Under the direction of Stephen Sheinkopf, associate professor of psychiatry and human behavior, researchers studied 118 children from ages one month to six years by measuring their heart and breathing rates. Of this group, 12 had autism, and the other 106 did not have autism. They were assessed every 6-12 months.

Normally, a person’s heart rate increases when inhaling and decreases when exhaling, a condition known as respiratory sinus arrhythmia (RSA). The autonomic nervous system controls these slight changes. These changes in breathing and heart rate are also linked to regulating emotions and paying attention to social cues, which are often impaired in autism.

The researchers found that all of the children showed similarly decreasing heart rate, which occurs over time with normal development. However, the children with autism were slower than their typical peers to develop the normal fluctuation of heart rate that occurs with breathing. Moreover, this phenomenon was most obvious after 18 months of age when behavioral symptoms of autism often emerge. By the age of 6, children with autism catch up with their typical peers in this trait (RSA) and demonstrate similar fluctuation of heart rate with breathing.

After observing the differences in heart rates and breathing between typical children and those with autism, researchers concluded, “RSA is a marker of functional status in autism rather than a cause of social deficits.” They suggest that the impairment of the autonomic nervous system occurs when autistic behaviors appear. Moreover, they note that children with autism have issues with physiological regulation––such as breathing and heart rate––that develop over time. Because this research only involved children who were exposed to drugs before birth, the researchers plan to study other groups of children to see if heart rate and breathing differences occur more widely.

In another recent Spectrum article, published May 17, 2019, and titled “Nerves that control heart rate may be offbeat in autistic adults,” Jessica Wright describes similar research involving adults. [To read this article, please click here.] She summarizes an article, “Reduced heart rate variability in adults with autism spectrum disorder,” published in Autism Research on April 10, 2019. [To read this research, please click here.]

Under the direction of Adam Guastella, professor of child and youth mental health at the University of Sydney in Australia, researchers examined resting heartbeats of 110 adults aged 16-41. Half of the participants had autism, and the other half included typical adults. All of the people in the study had no known heart conditions, and none of them were taking heart medications.

Usually, people’s resting heartbeat varies, showing flexibility and readiness to respond to environmental changes. However, researchers discovered that in adults with autism, the resting heart rate rarely varied. Moreover, those with autism had a higher baseline heart rate than the typical people. The lack of change in heart rate suggests issues with the autonomic nervous system responsible for reacting to social stimuli as well as heart rate and breathing. Researchers note that these results may explain issues with social skills common in autism as well as heart problems that can lead to early death in people with autism.

Of the participants in the study who had autism, half of them were taking medications, specifically antidepressants and antipsychotics. However, there was no difference in the heart rates between the adults with autism taking medications and those with autism who were not taking medications. Nonetheless, researchers indicate the need for further study to examine the impact of medications upon those with autism.

While both of these research studies indicate connections between heart rates, the autonomic nervous system, and autism that begin in infancy and continue through adulthood, more research clearly needs to be done. For example, what triggers at age 18 months may be responsible for the emergence of autistic behaviors? What is the connection between impairment of the autonomic nervous system and the apparent need for antidepressant and antipsychotic medications commonly prescribed for autism? What can be done to regulate heart rates so that adults with autism do not die young from heart conditions? Certainly, gaining knowledge regarding autism proves helpful, but more research must be done before we can hope to find a cure for autism.

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