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Depression and the immune system - expert analysis

New research out today suggests that the immune system can alter the workings of the brain - potentially causing depression. Sophie Dix explores, offering her take on the research and what it means for the future of mental health. 

What’s the issue?

350 million people affected by depression worldwide. For many it is a painful condition that affects every part of their life, and can leave those with the condition feeling  sad, empty, hopeless or guilty for weeks, months, and for many, even years.

Despite the condition affecting so many people, we know very little about depression, or how best to treat it. Anti-depressant drugs and psychological treatments, such as cognitive behavioural therapy, are effective but for some but not all. And many people will have to try many different treatments before they find one that works for them.

What does the research say?

New research published has taken an exciting new approach, offering hope for those who currently don’t have effective treatments. 

It’s part of a growing evidence base that shows our immune system can directly affect our mood – and for some may even be a cause of their depression, rather than a consequence of it. Essentially, we are learning that our immune system can alter the workings of the brain. With around one-third of depressed patients showing consistently high levels of inflammation.

It comes down to the inflammation that is part of the immune’s system response to danger. It is a hugely complicated process that helps our body fight off hostile forces. But if the inflammation gets out of hand then it can cause damage to our body and brain.

For example – rheumatoid arthritis is caused by the immune system attacking the joints in our body. Patients are often given precise anti-inflammatory drugs to calm down the immune response. But doctors and researchers noticed that these medications also had the added effect of improving their mood too.

And when mental health researchers scanned their brains, they found that the anti-inflammatory medicines were resulting in quite remarkable changes in the neuro-chemical circuitry in the brain.

Why is this exciting?

Current medications for depression generally work by targeting a certain type of neurotransmitter (which are the chemical messengers in the brain) called monoamines. But the development of these have stalled in recent years, with limited progress made in improving their effectiveness. And no fundamentally different approaches for new drugs have been discovered in the past 30 years.

This research provides an alternative route, and offers hope for the many people that don’t currently respond to existing medications. 

It brings hope of new drug discovery. Researchers will be able to explore what impact existing approved anti-inflammatory medications – which are currently used for other conditions but could be ‘repurposed’ - could have on depression.

And it offers up the potential for us to personalise medicines for those living with depression. If built upon, the research could lead to a simple blood test being enough to determine for some people what medication will be best to them. By exploring the levels of inflammation markers in their blood, we could potentially determine what medication should be prescribed, removing the trial and error that frustrates so many patients with depression. 

Moreover, it also helps to show that depression is not ‘all in the mind’. It can be caused by other systems in the body – an important development in the campaign to show that mental health is as important a condition as many other physical health complaints.

More broadly, the research shows that new thinking in mental health can open up new avenues. And this avenue of research may bring new treatments for other conditions such as schizophrenia.

As Professor Ed Bullmore, the Head of Psychiatry at the University of Cambridge says, "Recent history is telling us if we want to make therapeutic breakthroughs in an area which remains incredibly important in terms of disability and suffering then we've got to think differently."

The caveats

Despite all there is to be positive about, much more work is still needed to turn these findings into something meaningful for patients.

Drug discovery takes years, and will need focused funding on research to deliver effective new treatments for depression. Even then we’re only likely to see these help a specific sub-set of patients that show immune system changes – around 30 – 40% of those living with depression. 

However, the research still offers hope for the future, and shows the power of science in advancing our understanding of mental illness.

Last updated: 26 July 2017

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