Inflammation and anxiety: how are they linked?

It is not uncommon or unexpected to experience anxiety and depression when diagnosed with MS. What is not clear is exactly what is causing the mood disorders in MS – is it primarily the psychological impact of having a diagnosis of a chronic illness, or could it be the biological process of the disease itself?

New research just published provides evidence that the chemical changes associated with disease activity may be the cause of mood changes in MS.

In multiple sclerosis, immune cells enter the brain and/or spinal cord and cause inflammation and damage. This inflammation (the movement of immune cells into the tissue) is associated with the release of chemicals called cytokines that allow immune cells to communicate with one another. These cytokines can also affect other body systems.
In this study a group of researchers from Italy wanted to investigate the relationship between chemical markers of inflammation (the cytokines), and anxiety or depression in people with MS.

The study involved 405 people with relapsing remitting MS, of which more than a quarter were not on any immune modulating MS medications. They found that people experiencing a clinical relapse were more likely to also be suffering from anxiety or depression, than those in the remission phase. However, once the inflammation associated with this relapse subsided, the anxiety or depression also resolved. They also discovered that people that were showing new lesions on a MRI, but had no physical or clinical symptoms, were also more likely to be experiencing a state of anxiety or depression.

The researchers measured the levels of cytokines, which promote inflammation, in the fluid that surrounds the brain and spinal cord (cerebrospinal fluid, CSF). In people experiencing a relapse, IL-2 levels were higher in people that also suffered from anxiety, and TNF-alpha and IL-1beta levels were higher in people that reported symptoms of depression.

They also found that in the people in remission, high IL-2 levels were able to predict a relapse in the following six-months. Likewise, those with symptoms of anxiety were more likely to have a subsequent relapse.

Mood disorders in a person with MS have often been considered to be a consequence of MS disease awareness and changes in disability. However, this research highlights that this relationship may be more complex and that the chemical changes associated with inflammation in the brain can also cause mood disorders.

These results could lead to the development of tests that detect these markers of inflammation. If inflammation is present, treating neurologists and their patients could be more vigilant in looking out for, and treating, mood disorders. Also, if a patient starts to experience symptoms of anxiety or depression, this may indicate that inflammation is occurring in the brain or spinal cord and may predict new lesions or a relapse.

With thanks to MS Research Australia – the lead provider of research summaries on our website.