A new group of anti-inflammatory drugs may help treat depression, a new review finds.

And the link between these drugs and depression may shed light on the role that inflammation plays in the mental health condition, according to the review of previously published research.

The new anti-inflammatory drugs, which are currently used to treat autoimmune diseases such as rheumatoid arthritis and psoriasis, were found to also reduce symptoms of depression, according to the review, which was published today (Oct. 18) in the journal Molecular Psychiatry. [5 Controversial Mental Health Treatments]

In the studies that the researchers looked at in their review, these drugs were not tested out as treatments for depression, per se. Rather, the drugs were tested as treatments for the autoimmune conditions, but the researchers also collected data on the depression symptoms of the patients.

The findings show that future studies of these drugs as a treatment for people with depression are warranted, the researchers said.

"It's becoming increasingly clear to us that inflammation plays a role in depression, and now our review suggests that it may be possible to treat these individuals using some anti-inflammatory drugs," Dr. Golam Khandaker, a psychiatrist at the University of Cambridge in England and the senior author of the review, said in a statement.

"These are not your everyday anti-inflammatory drugs such as ibuprofen, however," Khandaker added.

The researchers focused on a group of drugs that target inflammatory proteins in the body called cytokines, according to the review. The immune system makes cytokines when it is fighting off an infection. In people with autoimmune diseases, the immune system produces these cytokines mistakenly, and they wind up damaging the person's own cells.

Previous studies have suggested that there is a link between the levels of cytokines in a person's blood and that person's risk for depression, the authors wrote. A previous study from this same group of researchers showed that children with high cytokine levels were more likely to develop depression or psychosis as young adults.

As a part of the new review, the researchers conducted several meta-analyses. In one meta-analysis, for example, they looked at seven randomized controlled trials that compared these "anti-cytokine" drugs to a placebo. The seven trials included a total of 2,370 people with autoimmune conditions, according to the review.

The patients who were given the anti-inflammatory drugs "showed significant improvement" in their symptoms of depression, compared to those who were given a placebo, the researchers wrote.

In a separate analysis, the researchers found that the anti-depressive effects of the drugs were not associated with improvements in physical symptoms. In other words, the drugs helped people's depression even when they didn't help treat the symptoms of the people's autoimmune condition.

"The results provide important clues regarding the role of inflammatory cytokines in depression," the researchers wrote in the study.

In addition, the findings suggested that anti-cytokine drugs might be particularly helpful for treating people with depression in cases where antidepressants don't work. Previous research has shown that in patients who have high levels of inflammation in the body, antidepressants are less likely to work, according to the review. It's possible, therefore, that anti-inflammatory drugs may be helpful for such cases of depression, the researchers wrote.

Because the researchers looked at studies in which the medications were used to treat autoimmune conditions, "it's too early to say whether these anti-cytokine drugs can be used in clinical practice for depression," Peter Jones, a professor of psychiatry, also at the University of Cambridge, and a co-author of the study, said in a statement.

"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," Jones said. In addition, some of the drugs "can have potentially serious side effects, which would need to be addressed," Jones added.

Originally published on Live Science.