Researchers say a new class of anti-inflammatory drugs could help treat depression.
Study leader Dr. Golam Khandaker, of the Department of Psychiatry at the University of Cambridge in the United Kingdom, and colleagues publish their results in the journal Molecular Psychiatry.
Inflammation is the result of the immune system's response to injury or infection, whereby immune cells release pro-inflammatory proteins - such as cytokines - to help fight harmful pathogens.
But this inflammatory response is not always helpful. Sometimes, the immune system mistakingly launches an attack on healthy cells and tissues, causing autoimmune diseases such as Crohn's disease, rheumatoid arthritis, and psoriasis.
Increasingly, researchers have suggested that the immune system and inflammation may also play a role in mental health. In 2014, for example, a study from Dr. Khandaker and team found that children with higher levels of cytokines and other "inflammatory markers" were at greater risk of depression and psychosis in later life.
In clinical trials, two new classes of anti-inflammatory drugs - anti-cytokine monoclonal antibodies and cytokine inhibitors - have been shown to reduce inflammation in a range of autoimmune diseases, and these drugs have already started to be administered to patients who do not respond to standard treatments.
Given the potential link between inflammation and depression, Dr. Khandaker and colleagues set out to investigate whether these drugs might also help alleviate symptoms of depression.
Anti-cytokines reduced depression symptoms in clinical trials
For their study, the researchers conducted a meta-analysis of 20 clinical trials that assessed the effects of anti-cytokine monoclonal antibodies and cytokine inhibitors in more than 5,000 patients with autoimmune diseases.
On investigating the additional benefits of the anti-cytokine medications in each trial - seven of which were randomized controlled trials involving a placebo - the team found that the drugs led to a significant reduction in symptoms of depression among participants, regardless of whether they were effective against autoimmune diseases.
While further studies are required, the researchers say their results suggest anti-cytokine medications may be a feasible treatment option for patients with depression - particularly for those who do not respond to current antidepressants.
"About a third of patients who are resistant to antidepressants show evidence of inflammation," notes Dr. Khandaker. "So, anti-inflammatory treatments could be relevant for a large number of people who suffer from depression."
"The current approach of a 'one-size-fits-all' medicine to treat depression is problematic. All currently available antidepressants target a particular type of neurotransmitter, but a third of patients do not respond to these drugs.
We are now entering the era of 'personalized medicine' where we can tailor treatments to individual patients. This approach is starting to show success in treating cancers, and it's possible that in future we would use anti-inflammatory drugs in psychiatry for certain patients with depression."
Dr. Golam Khandaker
Still, the team stresses there is still a long way to go before anti-cytokine medications will be used for depression in clinical practice.
"We will need clinical trials to test how effective they are in patients who do not have the chronic conditions for which the drugs have been developed, such as rheumatoid arthritis or Crohn's disease," says study co-author Prof. Peter Jones, of the Department of Psychiatry at Cambridge.
"On top of this, some existing drugs can have potentially serious side effects, which would need to be addressed," he adds.