Is There a Link Between Anxiety and Inflammation?

Anxiety is one of the most common mental health disorders across the United States.  It is quite common for a person to feel anxious at some point or the other due to a variety of reasons. In people with a diagnosed Anxiety Disorder, these periods of feeling anxious are more frequent and persistent than others. The severity of the anxiety episodes is also quite high. It becomes very difficult to control the emotions of these people and significantly impacts the quality of their lives.[1, 2, 3]

Anxiety Disorders can be categorized into Generalized Anxiety Disorder, Social Anxiety Disorder, Separation Anxiety Disorder, and Posttraumatic Stress Disorder. Some people have more than one form of anxiety disorder occurring simultaneously. The World Health Organization states that more than 200 million people across the globe suffer from some form of anxiety or the other.[1, 2, 3]

What exactly causes anxiety is still a matter of research according to experts but there are some factors which predispose an individual to getting this condition. This includes some parts of brain getting into an overdrive, imbalance of neurotransmitters, genetic makeup, substance use, and certain medical condition that cause chronic pain. The number of people being diagnosed with anxiety disorder has increased during the period of the current pandemic especially in the western world.[1, 2, 3]

Inflammation on the other hand can be described as the body’s natural reaction to a stimulus that the body perceives to be harmful like bacteria, virus, or other pathogens.  When the body detects any foreign invaders that it believes is a potential threat, the immune response gets active to fight it off resulting in inflammation.[1, 2, 3]

The inflammation subsides once the threat is taken care of. However, in some cases the inflammation is persistent. When this happens, the immune system starts to damage the healthy tissues and cells of the body.  Inflammation may occur in any part of the body, including the brain. While inflammation is a body’s natural way of protecting itself, researchers are now studying whether it may be a cause of mental disorders like anxiety.[1, 2, 3] This article highlights whether there is a link between anxiety disorder and inflammation.

Is There A Link Between Anxiety And Inflammation?

According to various research studies there is growing evidence of a link between inflammation and depression but more research is being done establish a link between anxiety and inflammation.  However, researchers are collecting evidence to establish a link between these two entities.  Anxiety is known to be associated with coronary artery disease and other metabolic disorders.  Because these conditions involve some amount of systemic inflammation and also the fact that depression and anxiety often go hand in hand researchers are of the belief that inflammation may have a role to play in the development of anxiety disorders.[3]

While studying inflammation, experts closed in to specific biomarkers that include tumor necrosis factor alpha, interleukin-6, and C-reactive protein.  The C reactive protein is released from the liver during inflammation.  The function of this protein is to bind to the markers. By doing this, it helps the immune system to fight away infections and pathogens. Interleukin-6 and TNF-Alpha are also inflammatory biomarkers that promote inflammation during an immune system response to pathogens.[3]

Over the years, evidence has been mounting as to the link between inflammation and mental health disorders.  In a study, the researchers analyzed inflammatory biomarkers including CRP, interleukin-6 and TNF alpha in 853 participants. They asked the participants to fill out questionnaires to assess how anxious they felt at that time and their general anxiety levels.[3]

After closely analyzing the data they found out that people with higher levels of anxiety had increased levels of inflammatory biomarkers like interleukin-6 and C reactive protein both in males and females.  A study published in the Journal of Psychiatric Research studied the link between inflammation and posttraumatic stress disorder.  In the study, the inflammatory biomarkers of 14 people with PTSD were analyzed and compared to 14 people who did not have this disorder.  The study showed that people with PTSD showed increased levels of pro-inflammatory biomarkers even though the sample size was very low.[3]

Further review of the link between PTSD and inflammation showed that there was a clear increase in the levels of TNF alpha and interleukin-6 in people with PTSD.  Another study was done on females with diabetes type-2 and phobic anxiety, a clear link was established between inflammatory markers and anxiety. The researchers concluded after the study that increased levels of leptin and other inflammatory markers was associated with high levels of anxiety.[3]

Now that a relationship between inflammation and anxiety was more or less established, one question that still remained unanswered was that whether anxiety causedinflammation or was it the other way round. To get to the bottom of this question, researchers thought of whether inducing a state of inflammation would increase anxiety levels.  For this, the researchers injected the participants of the study with lipopolysaccharide which is a component of cell membrane that induces an inflammatory response.[3]

They found out that as the levels of inflammatory markers increased the levels of anxiety also increased.  They also found that increased level of interleukin-6 was the inflammatory marker that was responsible for highest level of anxiety.  Similarly, in an animal model scientists induced gastrointestinal inflammation in mice and noted increased levels of anxiety in mice.  The study also showed that probiotic bacterium reversed the anxiety like behavior in mice [3].

This result led to another question that being whether gut bacteria had any role to play in mental disorders like anxiety.  This possible link may have not even been considered a few years back; however, today a clear link has been established.  The gastrointestinal system or the gut has a complicated nervous system of its own.  This is also called as enteric nervous system.  There is constant and complex two-way interaction between the enteric and central nervous system.[3]

Digging deep into this interaction, the researchers found that the communication between these two entities not only helped in maintaining gastrointestinal homeostasis but also had significant impact in the mood, motivation, and cognitive function of a person.  Thus there was a clear channel of communication between the gut bacteria and the brain through the enteric nervous system.  There are many studies that point towards a link between anxiety and gut bacteria in which a decrease in gut bacteria led to higher levels of anxiety.[3]

Researchers also investigated the possibility of whether probiotics may help treat anxiety disorders.  They came to the conclusion that while prebiotics had no effect on the anxiety levels probiotics had definite positive impact on the overall anxiety levels of the participants of the study.  Researchers suggested that one possible way through which gut bacteria may influence anxiety levels is by way of inflammation.  This is because gut bacteria has close links with both nervous system as well as the immune system of the body.[3]

Although links between gut bacteria and mental health have emerged, there is still a lot of research that needs to be done on how the gut bacteria influence the functioning of the brain.[3]

After all the research done, the question still remained whether anxiety caused inflammation or was the reverse of it true and the most important question that whether decreasing inflammation may improve anxiety.  For this, a study was done on approximately 300,000 people with a known diagnosis of cancer.  It is well known that people with cancer have a higher risk for psychiatric disorders like anxiety post diagnosis.[3]

The researchers’ analyzed information on how many participants developed mental health conditions like anxiety post diagnosis of cancer and whether they were taking any NSAIDs at least a year before their diagnosis.  After studying the data, they concluded that people who used NSAIDs before their diagnosis were at decreased risk for developing mental health conditions like depression and anxiety than participants who did not take antiinflammatories.[3]

In conclusion, even though there is mounting evidence of a clear link between inflammation and mental health disorders like anxiety, there is still a lot of work in terms of research that needs to be done before scientists get to the bottom of this extremely complex relationship.  The immune system is an extremely complicated subject and mental health disorders are something that is still not completely understood.  Adding to this is the relationship between gut bacteria and its role in influencing brain function makes the picture much more complicated.[1, 2, 3]

However, with time, researchers are optimistic that they will clear the fog surrounding this issue but what they are pretty sure of is that inflammation does have a role to play in the development of anxiety disorder but more research needs to be done in coming to a definite conclusion as to how and to what extent are inflammation and anxiety disorders are connected and use the information to treat complicated mental health conditions like anxiety.[1, 2, 3]

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