Chronic illnesses can have a major impact on your mental health. About 42 percent of cancer patients and 42 percent of people with rheumatoid arthritis suffer from depression. People with diabetes (27 percent), cardiovascular disease (17 percent) and Alzheimer’s (11 percent) are also at increased risk.
Another thing that all these diseases have in common is that inflammation is part of the clinical picture. And that is no coincidence. Research shows that inflammation can worsen mental problems.
“There is a lot of evidence that elevated levels of inflammation increase the risk of becoming depressed,” says Wolfgang Marx, an expert in nutritional psychiatry at Deakin University’s Food & Mood Center in Melbourne, Australia. ‘It also influences how we respond to treatment for depression. Inflammation seems to play a major role.’
The link between inflammation and depression
Depression has long been seen as a condition resulting from problems with neurotransmitters, says Marx. Serotonin and dopamine are two important neurotransmitters (molecules in the brain that transmit messages) that help regulate mood, motivation and emotions. The thought was always: if those molecules become out of balance, mental health problems will follow.
However, in recent decades, more and more research indicates that the immune system also plays an important role in mental health, and that inflammation in the body can lead to changes in the brain. As early as 1980, researchers discovered that people with psychosis had an increased number of immune cells in the blood. Since then, more researchers have linked cytokines (messengers within the immune system that are involved in initiating and limiting inflammatory responses) and diseases such as depression, bipolar disorders and schizophrenia.
It is undeniable that there is a connection. But researchers do not yet understand exactly how an inflammatory response leads to mental health problems. That is why they test different hypotheses. For example, Marx says, it’s possible that chronic inflammation weakens the production of serotonin and other neurotransmitters, prevents the production of new brain cells, or damages the production of new connections between brain cells. This effect is especially visible in the hippocampus, the part of the brain that regulates memory, emotions and moods.
Trauma leads to increased inflammation levels
To understand how inflammation-related depression develops, some scientists are looking at the risk factors for depression in childhood. It has been known for decades that a traumatic childhood increases the risk of depression as an adult – and also the risk that depression will be difficult to treat. This may be explained and treated by inflammation, says Andrea Danese, a child and adolescent psychologist at King’s College London.
Children who experience abuse and neglect in the first ten years of their lives have elevated levels of certain inflammatory molecules in their early thirties, Danese discovered with his research. Chronic stress can lead to inflammatory responses at any age, but exposure to stress early in life appears to be linked to more persistent forms of depression, he says.
New treatments for depression?
Antidepressants appear to have no effect in about thirty percent of people with depression. The highest inflammation values are often measured in this group. That is why researchers are trying to use their knowledge about inflammatory responses in the fight against depression.
An example is the drug infliximab, which is used to treat autoimmune diseases such as rheumatoid arthritis, psoriasis and Crohn’s disease. It may also have an antidepressant effect. In a 2013 study, sixty people were given infliximab or a placebo. The people who received the drug were twice as likely to report relief from depressive symptoms as the placebo group.
Lifestyle adjustments can also improve mental health, says Marx. Research shows that both a healthy diet and exercise have a positive effect on the microbiome, which plays a major role in controlling the immune system that regulates inflammatory responses.
A Mediterranean diet, high in legumes, fish, nuts and whole grain products, has been associated with a reduction in depressive symptoms in several studies. Other ways to combat inflammatory responses and support mental health include getting enough sleep, spending time outdoors and reducing stress through meditation.
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