What is psychoneuroimmunology?
Psychoneuroimmunology (PNI) is a relatively new field of study that looks at the interactions between your central nervous system (CNS) and your immune system. Researchers know that our CNS and immune system can communicate with each other, but they only recently started to understand how they do it and what it means for our health.
The nerves in your brain and spinal cord make up your CNS, while your immune system is made up of organs and cells that defend your body against infection. Both systems produce small molecules and proteins that can act as messengers between the two systems. In your CNS, these messengers include hormones and neurotransmitters. Your immune system, on the other hand, uses proteins called cytokines to communicate with your CNS.
What the research says
A cytokine is a small protein that’s released by cells, especially those in your immune system. There are many types of cytokines, but the ones that are generally stimulated by stress are called pro-inflammatory cytokines.
Under normal circumstances, your body releases pro-inflammatory cytokines in response to an infection or injury to help destroy germs or repair tissue. When you’re physically or emotionally stressed, your body also releases certain hormones, including epinephrine (adrenaline). These hormones can bind to specific receptors that signal for the production of pro-inflammatory cytokines.
Here’s a look at some of the recent research and discussions around PNI in the medical community:
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- A 2016 review of existing studies found that stressful experiences during childhood can increase the release of cytokines by your immune system. This is associated with an increased risk of mental illness in adulthood. Researchers believe that this early release of cytokines may cause changes in the brain that increase a person’s risk of developing a mental illness later in life.
- A 2015 article noted that rats produced different types of cytokines depending on the type of stress they experienced. For example, an injury produced one type of pro-inflammatory cytokine. Meanwhile, exposure to a social stressor, such as separation from a close family member, released a different type of pro-inflammatory cytokine.
- Another 2016 review found that both sleep disturbances and sleeping too much seemed to trigger the release of pro-inflammatory cytokines.
- A 2011 review exploring the link between stress and the immune system found that stress may play a role in conditions that affect the immune system, such as cancer, HIV, and inflammatory bowel disease.
What are some examples of PNI?
What does all of this new knowledge mean for our health? Keep reading to learn more about the role that PNI plays in several common conditions.
Psoriasis is a great example of how your immune system, CNS, mental health, and stress levels are all intertwined. It’s a chronic condition that causes your skin cells to grow too quickly. Your body usually sheds extra skin cells, but if you have psoriasis, these extra cells build up on your skin’s surface. This can lead to intense itching and pain.
The overgrowth of skin cells in psoriasis is due to the release of cytokines from your immune system. We know that psychological stress may worsen or trigger episodes of psoriasis. Indeed, people with psoriasis tend to have increased levels of cortisol, a stress hormone.
Your hypothalamus, which is part of your CNS, is responsible for cortisol production. When it senses stressors, it signals your nearby pituitary gland, which signals for cortisol production. This, in turn, can trigger the release of pro-inflammatory cytokines by your immune system. These cytokines then trigger an overgrowth of skin cells.
In addition, people with psoriasis often report having psychological conditions, such as depression, increased stress, and suicidal thoughts. Previous research has linked an increase in cytokine levels with major depression.
There’s currently no cure for psoriasis, but new developments in the field of PNI could change this in the future. In the meantime, here’s how to manage it at home.
A 2013 review of many studies exploring the relationship between PNI and cancer found evidence to suggest that:
- Women with genetic risk factors for developing cancer showed immune system abnormalities in response to stress.
- There appears to be a link in people with breast cancer between depression, the quality of social support they have, and immune cell activity.
- People with breast, cervical, or ovarian cancer who reported feeling stressed or lonely had abnormalities in their immune systems.
- Communication between the immune system and brain may impact symptoms that are related to cancer treatment, including fatigue, depression, and difficulty sleeping.
- Stressful experiences and depression may be associated with a poorer survival rate for several types of cancer.
Coronary artery disease
A review from 2010 looking at the relationship between stress, immune function, and coronary artery disease echoed other studies suggesting that psychological stress increases the production of pro-inflammatory cytokines.
This increase in pro-inflammatory cytokines is associated with an increase in heart rate and blood pressure. In addition, the production of cytokines by your immune system promotes feelings of sickness or fatigue. According to this review, this reaction isn’t immediately harmful. However, long-term stress and cytokine production may contribute to the development of cardiac disease.
The bottom line
PNI is a rapidly growing field of study that looks at the relationship between your CNS and immune system. While some of the research has raised more questions than answers, researchers now know that both physical and emotional stress can have a very real effect on your immune system.
The future of PNI will likely look at how this relationship impacts certain conditions, including cancer and psoriasis. It may even point researchers in the direction of long-awaited cures for both of these conditions, along with many others.