London: Growing evidence suggests that inflammation and the immune system may influence mental health, although researchers say there is still not enough evidence to use this connection as a treatment for conditions such as depression and anxiety.
Inflammation is the body’s natural immune response to injury or infection. It can cause familiar signs such as redness and swelling as immune cells work to fight infections and repair damaged tissue. However, inflammation can also occur with certain illnesses, while lower levels of inflammation may be associated with factors such as ageing and obesity.
Prof Daniel M Davis, head of life sciences at Imperial College London and author of Immune Health: A Myth-Busting Guide, explained that inflammation can be indicated by elevated levels of cytokines, molecules used by immune cells to communicate. Some cytokines can affect the brain and influence how people feel, potentially linking immune activity with changes in mood.
Research involving people with rheumatoid arthritis has found that medicines designed to block certain cytokines can also lead to improvements in mood. Brain scans suggest that these effects could be linked to changes in brain activity caused by blocking inflammatory signals.
Other research has also pointed to a possible connection between inflammation and later mental health problems. A study involving nearly 5,000 children found that those with above-average levels of the cytokine IL-6 at age nine, despite showing no signs of depression at the time, were more likely to experience depression by age 18.
Research among adults has similarly identified an association between immune-related illnesses and earlier diagnoses of psychiatric conditions, including depression and anxiety.
However, scientists stress that the relationship remains complex and is not yet fully understood. While several studies indicate an overlap between the immune system and mental health, researchers still need to determine which people could benefit from targeting inflammation and which specific parts of the immune system could be safely targeted.
For now, inflammation should not be considered a proven cause or treatment for depression or anxiety, and more research is needed to understand how the two may be connected.
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