Home Mental Health & Well-Being How Is Inflammation Contributing to Mental Disorders?

How Is Inflammation Contributing to Mental Disorders?

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Our brain is connected to our body via the spinal cord, forming the central nervous system. There is no doubt that the brain and body are linked – so why are physical and mental health often managed separately? 

Physical illness is frequently treated by doctors or nurses with a medical “human body” background. Yet, mental illness is usually treated by psychologists/psychiatrists with a mental health background. We can even see this division when looking at university modules. Very few establishments offer degrees that include detailed combinations of both physical and mental health. These two branches of health are frequently viewed in isolation.  

Yet, there are some obvious links between physical and mental health that you are likely to be aware of. Perhaps a more common connection is the impact of a physical illness on an individual’s mental state. For example, a cancer diagnosis could increase the chances of that same individual experiencing depression or anxiety due to the worry and outlook on the disease. Additionally, this connection can also be viewed the other way around. For example, the connection between a diagnosis of anxiety and the impact this could have on the individual’s physical health, such as an increased heart rate, or a dry mouth. However, these connections lead us to wonder whether there is more to this mind-body connection than we currently know and understand.

What is inflammation?

One developing area that focuses on the association between mental and physical illness (specifically the role of our immune system) is known as immuno-psychiatry. This area explores the connection between inflammation in the body and the impact of this on an individual’s mental health. Usually, inflammation is a good and much-needed process for us all. If you cut your skin from a fall, the body’s natural inflammatory response will be triggered. This response can cause swelling, redness, and bruising, stopping bacteria from entering the cut. This process is known as acute inflammation and involves your body preventing infection and promoting healing. However, other circumstances can cause the body to activate a long-term immune response. This is known as chronic inflammation and involves the response continuing for longer than is required. A wide range of factors can contribute to chronic inflammation. These can include factors such as stress, excessive alcohol consumption, high BMI, untreated acute inflammation, autoimmune disorders, and harmful toxin exposure. This presence of chronic inflammation in the brain is what can impact the occurrence of certain mental illnesses such as depression, anxiety, and OCD. 

Inflammation and depression

Research suggests that inflammatory markers (present in the blood during inflammation), can break the brain-body barrier, causing brain inflammation. This then affects crucial neural circuits which can contribute to depression. One study found that individuals suffering from depression had higher levels of inflammation in their bodies compared with those who were not suffering from depression. These findings were concluded regardless of socioeconomic background, illness, or unhealthy behaviours. Interestingly, other studies have also found that when individuals are provided with an inflammatory-causing drug (such as the drugs used for some cancer treatments), higher levels of depression have been found. This is because pro-inflammatory agents can create reduced emotional responses from individuals. 

However, fully understanding the role that inflammation has on depression is complex and requires more research. Some research suggests that inflammation could have an impact on depression due to inflammation rising anhedonia. This means that the inability to experience pleasure is increased, which could contribute to a depressive mood. Other research has suggested that inflammation could slow down thought and movement, again contributing to depression. Further research also implies that inflammation could reduce the release of dopamine (the chemical released that makes you ‘feel good’) or disrupt the connections of the brain’s reward circuit.

Inflammation and OCD

One study found that brain inflammation in individuals with OCD was more than 30% higher than in those without. They also found the inflammation located in the areas of the brain that function differently in an individual with OCD. Interestingly, it was also found that experiencing stress and anxiety caused by resisting compulsions, increased levels of inflammation.

Currently, two known conditions contribute to OCD through the triggering of an immune response. These conditions contribute to a rapid onset of OCD (often overnight) in children, due to an infection. One of these conditions is paediatric acute-onset neuropsychiatric syndrome (PANS), which is a mismanaged immune response to a variety of triggers. This is a more general term that does not specify the type of infection. The other condition is paediatric autoimmune neuropsychiatric disorder associated with streptococcal infections (PANDAS), which occurs due to a mismanaged immune response to a streptococcal infection. It is thought that this can contribute to OCD due to autoimmune antibodies mistakenly attacking brain tissue

Inflammation and anxiety

Additionally, there have also been links identified between brain inflammation and anxiety disorder. This connection involves inflammatory cytokines – which are signalling proteins of the immune system that tell your body to begin repair after an injury and alert your brain of the injury. These inflammatory cytokines result in a change of behaviour. For example, if you were to burn your hand on a stove, this would result in you being extra careful around heat in the future. This could then result in reduced motivation and motor activity, which could lead to changes in behaviour and increased anxiety levels. However, there is still further research needed to understand whether anxiety causes inflammation, or vice versa.

Interestingly, the role of inflammation and anxiety has also been researched in individuals suffering from long Covid. This specifically looked at the role of biomarkers in the blood. One biomarker researched was a marker that indicated the activation of glial cells (these cells provide support to neurons). Activation of these cells suggests brain inflammation. Levels of this biomarker (as well as another biomarker indicating damaged nerve cells) were tested in patients who had either been in recovery from acute Covid for 3 months or were showing neurological symptoms of long-Covid. It was found that individuals suffering from anxiety had higher levels of brain inflammation as indicated by the biomarker. The severity of the anxiety also increased in relation to the rate of brain inflammation found. This does suggest that the connection between anxiety symptoms and biomarkers can indicate physical changes in the brain, which could contribute to chronic anxiety.

The relationship between inflammation and mental illness is extremely interesting and perhaps suggests a different take on treatment. Currently, research is being conducted into treatments for mental illness that focus on targeting and treating the underlying inflammatory processes. This includes anti-inflammatory medicine (including ibuprofen and aspirin), supplements targeting inflammation, and specific anti-inflammatory diets.

Leah Bailie is a pet lover based in the UK.


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