Man and dog lying on bed with sad expressions.

The link between depression and inflammation

23 Nov 2022 • 1 min read

Depression is often caused by life events, but a new culprit has been identified – your own immune system. The Royal College of Psychiatrists says one in five of us will develop depression at some point in our lives. No wonder the number of prescriptions for antidepressants has more than doubled in the past decade. Life events like divorce and low levels of serotonin – the ‘happy’ hormone – are often identified as the cause of feeling depressed but in a surprising twist, experts now say inflammation in the body could be to blame. Handpicked content: How stress affects the immune system

What is inflammation?

When our immune system is under attack from injuries or infection, it triggers an inflammatory response to stimulate blood flow and other fluids to help with healing wounds or prevent further damage. But problems arise when it misfires, or ‘overreacts’, and continues long-term, for example in autoimmune diseases like rheumatoid arthritis or allergies such as hay fever.

How does inflammation cause depression?

Our ‘fight or flight’ response to stress triggers inflammation throughout the body. Other risk factors for depression – poor diet, sleep loss, illness and obesity – are also strongly associated with inflammation. We tend to feel a bit down and show signs of feeling depressed when we’re ill: sleeping more, eating less, struggling to concentrate, avoiding friends or family. It’s called ‘sickness behaviour’, but it’s a lot like depression and scientists say this is because it’s caused by inflammation. Handpicked content: About stress and how you can manage yours

What does the research say?

Experts say that around one in three people who feel depressed also have high levels of inflammation, while a study by the University of Toronto in 2015 discovered that inflammation was, on average, 30% higher in the brains of those with clinical depression. Another study published in the journal Biological Psychiatry in 2017 found that some inflammatory markers were associated with having suicidal thoughts.

Are you at risk?

Although there is a link between inflammation and feeling depressed, a clinical review in 2011 concluded that inflammation is ‘neither necessary nor sufficient’ to cause depression. So not everyone with high levels of inflammation is depressed and not everyone with depression will have high levels of inflammation. The reviewers went on to say some of us may only develop depression ‘in response to all but the highest levels of inflammatory stimulation’, while even low-level inflammation may trigger symptoms in others. The good news is that reducing inflammation tends to relieve depression. In fact, scientists say antidepressants may work by subduing the inflammatory response. Talk to your GP if you think you may be feeling depressed.
Advice is for information only and should not replace medical care. Please consult a doctor or healthcare professional before trying any remedies.
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