I've recently been learning about polyvagal theory at the suggestion of my therapist, and through that research have seen that it is connected to trauma, Autism, Schizophrenia, and many other mental health disorders (I am not diagnosed with any of these disorders, nor do I know much about them). As it stands, I have a theory that I'm playing with about how this connects to ADHD as well. If I'm wrong, please feel free to correct me in the comments.
But first, what is the Polyvagal Theory?
There is a system of nerves that leads directly from your organs to the brain, and it isn't JUST for making them run. The mainline of this nerve is called the vagal nerve, which splits into several sections. This nerve's job is to change the way your body works when you are in danger, and it has three different modes that it can make your body go into.
IT IS NOT CONTROLLED BY CONSCIOUS THOUGHT.
The first is it lets you feel safe and social. It's our body's default state. When your body doesn't perceive any threats, it feels good and changes your body into a relaxed state. Your heart rate slows, your digestive system is working at peak levels, your facial muscles and vocal cords use more energy and move around more frequently, we hear mid-tone sounds more clearly, and the muscles around your limbs relax. These changes in our body not only increase your own feelings of safety but the people around you can automatically pick up on these changes and adopt them as well. It is the last of the modes that your body develops and allows you to use executive functioning skills optimally.
This is when you're feeling creeped out, anxious, or are getting really excited. Your body is having the fight or flight response and is changing the way that you see the world around you. Your heart rate increases, you have higher pain tolerance, your digestion slows, your facial expression goes flat, and you start to lose the ability to hear mid-tone sounds while becoming sensitive to high-pitched and low-toned noises. Your body is forcing you to listen for the tiger's growl, the snake in the grass, or the distant scream of someone who is in trouble. This is the second mode that your body develops and it keeps you safe by moving your mental and physical energy to the places that are most important when finding a threat.
If your body believes that death is imminent it will move into the freeze response. This is where a person shuts down, dissociates, and feigns death. This is an active trauma response and is not something that a person can control. It is automatic and bypasses our higher brain capabilities. This is the first mode that your body develops, and it's created to help you when you are unable to escape or fight off an attack.
How does it work?
Your body moves through each of these modes in a set order. First, you are safe. Then, you are on high-alert. Finally, you freeze. After the threat is done, you move backward through the system in the same order to help you make a quick getaway to safety.
In a Neurotypical Brain...
A person can swap back and forth between the social and high alert state as needed. They might even activate the high alert state on purpose when they are getting ready for a race or going to the gym. The freeze response will only be reserved for large threats and active trauma.
Anxiety is the over-activation of this nerve, making us feel unsafe in a world with fewer sabertooth tigers and a significantly higher amount of deadlines than this system was developed for. Trauma can also impact the sensitivity of this system. In Autism, there may be an under-development in the way this nerve functions which causes them to be stuck in fight, flight, and freeze. This explains the constant over-stimulation that they experience.
A Theory on ADHD
A special note on this section: This is just the musings of my brain and in no way are actually something I've read or learned about. This is pure musings and not tested or verified in any way.
I've talked in a previous post about the ADHD brain not having enough stimulation, which makes the ADHD body and brain become restless and begin seeking outside sources of stimulation (sweets, drugs/alcohol, thrill-seeking, etc). I also know that the chemicals involved in ADHD are related to dopamine and the fight/flight/freeze response. So...
What if part of ADHD is an over-reaction in this system that goes both in the fight/flight/freeze direction (hyper-activity and daydreaming) as well as in the relaxed direction? This would explain why many ADHDers fall asleep when they are calm.
As I have looked deeper into the polyvagal theory I have learned that there is research being done (like this study) on this subject. In people with ADHD, researchers are finding that the vagal nerve is affecting heart function, which could be a sign of abnormal complex cardiac functioning. What we do know is that this nerve is connected to the prefrontal cortex which is developmentally delayed in people with ADHD.
Though I'm not a scientist or medical professional, I believe that this might lead to a whole new understanding of ADHD and its effects on the body. Hopefully, this may lead to new treatment options in people with more persistent symptoms.