Researcher Brad Ferguson delves deeper into the role that stress plays in the GI problems so common among kids with autism
Post by psychologist and neuroscientist Brad Ferguson, a doctoral student at the University of Missouri Thompson Center for Autism & Neurodevelopmental Disorders, in Columbia. The center is one of 14 sites in the Autism Speaks Autism Treatment Network (ATN).
I’m pleased to have this opportunity to update the Autism Speaks community on the progress of our investigations into the role that stress plays in the gastrointestinal issues that are so common among children and teens who have autism.
This research is made possible by the support of the Autism Speaks ATN in its federally funded role as the Autism Intervention Research Network on Physical Health (AIR-P).
As you may recall from my first post describing the first phase of this study, we enrolled 120 children and teens with autism, ages 6 to 18. The first time they came to our laboratories, they allowed us to monitor their heart rates and measure the sweat on their fingertips to gauge their stress levels. During the course of the exercise, each child underwent two painless but strongly sensory experiences: putting their hands in very cold water and then holding a vibrating massager.
We found that children with the strongest stress response to the tests – as indicated by increased heart rate and sweating – tended to be the same children whose parents reported constipation and other GI problems on a detailed questionnaire we gave them. My colleague Sarah Marler and I presented our team’s early findings at the International Meeting for Autism Research (IMFAR) last year. (Dr. Marler directs the Medical Exploration of Neurodevelopmental Disorder Clinic at Vanderbilt University, another site in the Autism Speaks ATN.)
Cortisol: The Stress Hormone
Today, I’d like to tell you about the second phase of our study. In this phase, we looked at levels of the so-called “stress hormone” cortisol immediately following the same stress tests described above. Cortisol levels can tell us how the body’s hormonal, or endocrine, system is responding to stress. This deepens the understanding we gained by tracking our study participants’ heart rates and sweat responses.
A powerful hormone, cortisol prepares the body to deal with danger. In other words, it triggers what is often called the “fight or flight” response.
When the brain senses danger, it sends a rapid-fire signal to the adrenal glands (located atop the kidneys). The adrenal glands release cortisol directly into the blood stream. Heart rate shoots up along with blood pressure.
Cortisol also places the immune system and brain on “high alert.”
Clearly, this “fight or flight” reaction is important for survival in a life-threatening situation. It becomes a problem if it occurs chronically in response to everyday sights, sounds and smells. Unfortunately, this is exactly what we suspect happens with many people who have autism.
Cytokines: Messengers of the Immune System
In addition to cortisol, we also looked at several important messenger molecules in the immune system. They’re called cytokines, and they ramp up or ramp down the immune response to protect the body from infection.
There are many types of cytokines. We looked specifically at interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha). Studies suggest that their levels tend to be increased in many people who have autism – as well as people who have irritable bowel syndrome (IBS). IBS is marked by stomach pain and alternating diarrhea and constipation. To a less extreme extent, these are also the GI symptoms we often see in children who have autism.
What’s more, we know that stress can exacerbate IBS. So we thought it important to see if stress influences these IBS-linked cytokines in the kids participating in our study.
Day 2 in the research lab
When each participant came in for this second phase of the study, the day started with a spit sample to measure cortisol levels and a blood sample to measure TNF-alpha and IL-6. In addition, we recorded heart rate and fingertip sweat as we did in the study’s first phase.
Just like they did earlier, the kids then placed their hands in cold water (image at top) and held the vibrating massager (at right).
As before, the idea was to provide a painless but uncomfortable sensory experience. We then took another spit sample to look for changes in cortisol levels.
What did we find?
We found that the children and teens with the biggest increase in cortisol level tended to be the same children and teens whose parents had reported GI problems such as constipation and lower abdominal pain.
We also analyzed their cytokine levels, from the blood tests taken at the beginning of the day. Here too, we found a clear association. The kids with the highest TNF-alpha levels – meaning those with the highest body-wide inflammation – also tended to have parent-reported GI problems.
Where do we go from here?
Our team continues follow up with the families who participated in this study. In particular, we want to track any associations between the children’s immune and stress responses and how they respond to dietary, behavioral and medical management of their GI symptoms.
Our study’s findings raise the possibility that stress-reducing interventions may provide additional benefit.
But as with all relatively small, preliminary studies, we want to see independent confirmation of our findings by other researchers. Also, it bears mentioning that our findings show a correlation but not necessarily causation. In other words, we found an association between increased stress response and autism-associated GI problems. But we don’t know that the GI stress caused the children’s GI problems.
In either case, it still might be possible that doctors will someday use blood and saliva tests – or even heart rate and sweat measurements – to guide personalized treatment of GI disorders in patients who have autism.
Bottom line: We hope our study will help improve quality of life for those with autism and GI problems.
We want to thank all the kids and families who participated in this work, as well as the Autism Speaks community for its support of the Autism Speaks Autism Treatment Network.