Understanding The Parasympathetic Nervous System
You may have heard of the parasympathetic nervous system and its role in mental health problems. Increasingly, understanding the parasympathetic nervous system is known to be essential to good mental healthcare. But what is it, and as a patient can you do anything to help it function better? Let’s break it down.
What is the parasympathetic nervous system?
Understanding the parasympathetic nervous system (PSNS) requires first understanding what we mean in medical terms by nerves. So what are nerves?
Nerves are like wires carrying electrical signals between your brain and the other parts of your body. These signals sustain certain key functions such as your breathing, digestion, and sweating. They also help you to move your muscles and to feel sensations. For example, when you stub your toe, nerves carry the signal, creating pain as a warning to protect you from harm.
The nervous system sends messages between the brain and the rest of the body, including your organs. The nervous system governs a person’s ability to breathe, move, think, hear, and much more. Your clever nervous system is always working, even while you sleep!
The nervous system has two key parts:
- The central nervous system – which is comprised of the brain and spinal cord.
- The peripheral nervous system – which is comprised of nerves reaching off from the spinal cord to all of the body’s other parts.
The autonomic nervous system is a part of the peripheral nervous system that governs involuntary bodily activities such as blood pressure, breathing, heart rate, digestion and even sexual arousal. In turn, one of the components of the autonomic nervous system is the parasympathetic nervous system.
The parasympathetic nervous system is a nexus of nerves that works to relax your body after times of stress or threat. In addition, it helps to govern key processes such as digestion when you are feeling at ease and safe. This is why the parasympathetic nervous system is sometimes nicknamed ‘rest and digest’.
The parasympathetic nervous system works to balance its partner, your sympathetic nervous system, which is also part of the autonomic nervous system. On the one hand, your sympathetic nervous system governs the body’s ‘fight or flight’ response, while on the other, your parasympathetic nervous system governs your body’s ability to relax, to ‘rest and digest’. The parasympathetic nervous system helps govern day to day processes like resting heart rate, resting breathing rate, and metabolism. In essence, your parasympathetic nervous system helps your body to stay in a relaxed state.
How does the parasympathetic nervous system work?
The PSNS is made up of a nexus of little neurons and large nerves spread throughout the body and regulate things like digestion, heart rate, breathing, and sexual arousal. It acts as a counterweight to the sympathetic nervous system, which runs your body’s fight or flight response. If there were no parasympathetic nervous system, your body would simply be running on high alert. Existing in ‘fight or flight’ mode for extended periods of time (with elevated heart rate for example) is not good for the body, or for mental health.
Dr Christos Kouimtsidis, Consultant Psychiatrist, at The London Psychiatry Centre says: “Day to day there are many possible events that can cause a fight or flight response; from an argument with a spouse to the pressure of a job interview or even being late for an appointment. These things can activate the sympathetic nervous system, causing the body to be in a state of high alert – heart rate and blood pressure go up, your pupils dilate, the body is reacting as if in danger (when often in the modern world, the ‘threat’ is not actually physical).”
In counterbalance to this sympathetic nervous system response, the parasympathetic nervous performs the function of ‘downregulating’, lowering your heart rate for example. The PSNS mostly works via a nerve known as the vagus nerve, which transmits messages from the brain to the body, and vice versa from the body to the brain. The vagus nerve encompasses around 75% of the PSNS nerve fibres. It is linked to a number of your organs, including the heart, lungs and parts of the digestive tract, reaching off into smaller nerves throughout your body.
If your parasympathetic nervous system is working well, it lowers your chances of stroke and cardiac problems, stimulates digestive metabolism and gut health, and reduces migraines. Better parasympathetic nervous system function helps better health overall, both physically and mentally. Understanding the parasympathetic nervous system is crucial for practitioners working in mental health – in fact, it is a mistake to crudely separate physical/mental health.
Have you heard the term ‘brain-gut connection’? The vagus nerve sends messages from the brain to the digestive system and vice versa. Practitioners often use the term ‘brain-gut connection’ to talk about the role that the vagus nerve plays in disorders such as depression, post-traumatic stress disorder, and inflammatory bowel disease. These conditions are believed to encompass both the brain and the gut, and science is trying to understand the various ways how. Increasingly research is being conducted into brain-gut connection, and how gut dysbiosis is involved in depression. The role that the vagus nerve plays in disorders such as these is increasingly the focus of researchers trying to better the health of patients. Scientists are interested in the possibilities for ‘vagus nerve stimulation’ to improve PSNS function.
How does depression affect the parasympathetic nervous system?
In popular culture, depression is often talked about as being ‘in the mind’ but the truth is much more complicated than that. Depression affects various systems in the body. When we speak of the ‘brain-gut connection’ for example, the relationship is two way, and researchers have found that ‘gut dysbiosis is involved in the pathogenesis of depression’ – in other words, in the development and progression of depression.
That said, depression is a very heterogeneous disorder, coming in many forms. Many people with depression do not suffer with unipolar depression, but experience anxiety and/or bipolarity too. In unipolar depression (low mood, flat affect, hypoarousal), the parasympathetic nervous system may be dominant. In patients with anxiety, the sympathetic nervous system may be over-functioning (fight or flight, high alert state). Remember, the sympathetic nervous system and the parasympathetic nervous system act as counterweights. Either way, increasingly depression is now understood to be disruptive to the autonomic nervous system.
Indeed research has revealed that depression tends to alter autonomic nervous system function, as revealed in studies of heart rate variability comparing depressed patients against healthy ones. Patients with depression are at increased risk of cardiac problems.
In other words, depression is not simply ‘in your mind’, it’s in the function of your body too.
How do I activate my parasympathetic nervous system?
While depression affects the parasympathetic nervous system and vice versa, the good news is that we are not powerless to affect our PSNS. Long-term, keeping depression at bay will encompass patient self-care techniques that activate the parasympathetic nervous system. Indeed research has shown that lifestyle (nutrition, exercise and sleep habits) can play a key role in depression. Exercise, meditation, even a really good belly laugh can activate your parasympathetic nervous system.
The London Psychiatry Centre has long been a proponent of increasing the mental health profession’s understanding of the parasympathetic nervous system. We have been at the forefront of understanding this connection and bringing it into patient care.
For example, for many years we have provided cardiac screening for our patients. We have also pioneered repetitive transcranial magnetic stimulation (rTMS) in the UK, which research has shown exerts a parasympathetic response in the autonomic nervous system including in blood pressure and heart rate control. Here at The London Psychiatry Centre, awareness of the ways in which the body and brain interact is central to everything we do, putting us at the leading edge of mental health treatment. Our team encompasses cardiologists, endocrinologists, psychiatrists, psychologists, nutritionists and more, truly embodying ‘joined up care’. We can offer telephone or video call appointments from anywhere in the UK too. To find out how we can help, get in touch with us using the below contact details.
