Clinical trial suggests an anti-inflammatory drug could relieve difficult-to-treat depression

A recent clinical trial suggests that treating the immune system with an anti-inflammatory drug could relieve symptoms in people with difficult-to-treat depression. The research provides early evidence that lowering inflammation levels tends to improve mood, fatigue, and anxiety for these individuals. The findings were published in the medical journal JAMA Psychiatry.

Standard medical treatments for depression typically focus on brain chemistry. These medications are designed to alter levels of neurotransmitters like serotonin and dopamine. While these drugs help many people, about one in three individuals with depression do not experience adequate relief from them.

Scientists suspect that other biological systems might be responsible for mood disorders in some patients. Recent research indicates that approximately one third of people with depression have persistent signs of inflammation in their blood. This suggests their symptoms might be linked to an overactive immune system rather than solely to chemical imbalances in the brain.

Inflammation is the natural response the body uses to heal injuries and fight infections. In some cases, the immune system remains engaged at a low level for long periods. This state of low-grade systemic inflammation can affect the brain and alter a person’s behavior and mood.

During an immune response, the body produces proteins called cytokines. Cytokines act as chemical messengers that signal the immune system to take action. High levels of a specific cytokine called interleukin 6 have been consistently associated with depression in previous observational studies.

Previous work by the research team utilized a genetic technique called Mendelian randomization. This method examines natural genetic variations in large populations to help scientists separate basic correlations from true biological causes. Those genetic studies provided strong evidence pointing to the interleukin 6 pathway as a causal factor for depression, prompting the team to conduct a clinical trial.

Lead author Éimear M. Foley, a researcher at the University of Bristol, and her colleagues wanted to test this connection in a practical setting. They designed a study to see if blocking the biological pathway of interleukin 6 could reduce depression symptoms. To accomplish this, they utilized an existing arthritis drug called tocilizumab.

Tocilizumab is an immunotherapy medication that inhibits the body’s receptors for interleukin 6. By blocking these receptors, the drug reduces the overall inflammatory response. The researchers aimed to determine if administering this drug to depressed patients with high inflammation would lead to noticeable improvements.

The scientists organized a four-week, randomized, placebo-controlled trial. They recruited thirty adults who were currently experiencing moderate to severe depression. All the participants had a history of trying standard antidepressants without finding sufficient relief.

To ensure they were testing the right population, the researchers required participants to show signs of persistent low-grade inflammation. They measured a specific substance in the blood called high-sensitivity C-reactive protein. This protein is produced by the liver and serves as a reliable marker of overall inflammation in the body.

Participants had to take two separate blood tests two weeks apart. Both tests needed to show elevated levels of the C-reactive protein. This requirement helped the scientists confirm that the inflammation was a chronic issue and not just a temporary reaction to a passing cold or minor infection.

The researchers randomly divided the thirty participants into two groups. Fourteen individuals received a single intravenous infusion of tocilizumab. The dosage was calculated based on each patient’s specific body weight.

The remaining sixteen participants received a single intravenous infusion of a simple saltwater placebo. The study was double-blind, meaning neither the patients nor the researchers knew who received the actual drug until the trial concluded. This design helps prevent expectations from influencing the recorded results.

Following the infusion, the scientists tracked the participants for twenty-eight days. They conducted detailed assessments at the one-week, two-week, and four-week marks. During these check-ins, the participants filled out validated questionnaires to evaluate their physical and psychological symptoms.

The researchers were particularly interested in somatic symptoms of depression. Somatic symptoms are the physical manifestations of the disorder, such as profound fatigue, changes in appetite, and sleep disturbances. They also tracked overall depression severity, anxiety, and general quality of life.

Because this was a small proof-of-concept study, the researchers did not expect the findings to reach statistical significance. Statistical significance is a mathematical standard used to confidently rule out chance in scientific data. The results did not meet this strict threshold, but the data showed a consistent pattern of improvement favoring the medication.

Participants who received tocilizumab experienced a stepwise reduction in their symptoms. This means their condition tended to improve gradually over time, with the most noticeable benefits appearing at the final twenty-eight-day assessment. The group receiving the medication reported steady reductions in both somatic symptoms and overall depression severity.

The researchers also observed improvements in individual symptoms. The tocilizumab group reported feeling less fatigued, having better concentration, and experiencing an improved appetite. They also reported fewer feelings of worthlessness and less physical agitation compared to the placebo group.

At the end of the four-week period, about 54 percent of the participants in the medication group had achieved remission from their depression. Remission means their symptoms were reduced to a level no longer considered clinically depressed. In the placebo group, about 31 percent of participants reached remission.

The researchers calculated that five patients would need to receive the medication for one additional person to achieve remission. This metric helps doctors understand the practical benefit of a drug in a clinical setting. For context, common antidepressants typically require treating about seven people to see one extra positive outcome.

The study also revealed a relationship between initial inflammation levels and treatment success. Participants who had higher levels of C-reactive protein at the start of the study tended to show the greatest improvements after receiving tocilizumab. Interestingly, initial levels of interleukin 6 did not predict the treatment response as accurately as the C-reactive protein levels did.

This finding provides evidence that a simple blood test for C-reactive protein could help doctors identify suitable candidates for immunotherapy. The procedures were well tolerated by the participants. No serious adverse events or medical complications were reported during the trial.

The authors note that the study has several limitations. The small sample size means that the positive trends cannot definitively prove the drug is effective. The four-week follow-up period was also relatively short, leaving it unknown if the benefits would last over months or years.

The participant group lacked significant demographic diversity, which limits how well the findings might apply to the broader population. The researchers emphasize that larger clinical trials with more diverse participants are required. These future studies should test the treatment over a longer period and potentially use repeated doses of the medication.

Current psychiatric care often relies on a trial and error approach when prescribing antidepressants. A patient might try several medications before finding one that works. The approach tested in this study points toward precision medicine, a strategy where treatments are specifically chosen to match a person’s unique biological makeup.

Despite its limitations, the trial represents an important step forward in psychiatric research. The findings suggest that targeting a patient’s specific immune profile could offer a new path forward. Such personalized approaches might eventually provide relief to individuals who have struggled with treatment-resistant depression for years.

The study, “Interleukin 6 as a Treatment Target for Depression: A Proof-of-Concept Randomized Clinical Trial,” was authored by Éimear M. Foley, Nicholas Turner, Ruta Margelyte, Hannah J. Jones, Muzaffer Kaser, Glyn Lewis, Peter B. Jones, and Golam M. Khandaker.