Common antidepressant drugs known as selective serotonin reuptake inhibitors are linked to a reduced risk of death among cancer patients undergoing immunotherapy, according to research from Taiwan published in the journal PLOS Medicine.
Scientists evaluated data from cancer patients diagnosed with malignant tumors who were also suffering from depression or anxiety disorders while receiving immunotherapy. The study compared 1,567 patients taking selective serotonin reuptake inhibitors, or SSRIs, with an identical group of 1,567 patients who were prescribed benzodiazepines.
Over a two-year follow-up period, 23.5 percent of patients in the SSRI group died, compared to 34.4 percent of those in the benzodiazepine group. When accounting for the timing of death, researchers found that SSRI use was associated with approximately a 37 percent reduction in overall mortality risk.
Researchers suggested that the potential survival benefit may stem from how antidepressants interact with the human immune system. SSRIs block the serotonin transporter, a protein that can suppress the activity of T-cells. By inhibiting this transporter, the medications may potentially enable immune cells to attack tumors more effectively during immunotherapy treatment.
To test this hypothesis, scientists analyzed more than 8,200 tumor samples across 20 different types of cancer. The analysis revealed that in 13 of the 20 cancer types studied, higher activity of the serotonin transporter gene was correlated with a weaker T-cell response against cancer cells.
Antidepressant classes and cancer care
SSRIs, or selective serotonin reuptake inhibitors, are widely prescribed antidepressant medications designed to raise serotonin levels in the central nervous system. Benzodiazepines belong to a separate drug class typically used for immediate anxiety relief or sleep management. Oncology patients often receive these medications to manage depression and emotional distress following a cancer diagnosis.
Immunotherapy has emerged as a cornerstone of modern cancer treatment, helping the immune system identify and destroy tumor cells. The treatment relies heavily on T-cells, a type of white blood cell responsible for attacking abnormal cells. When T-cell activity is constrained, tumor cells can evade detection, making mechanisms that support T-cell performance an important area of study.
The findings were published in PLOS Medicine, a peer-reviewed open-access medical journal published by the Public Library of Science that covers major global health topics and clinical trials.
Study limitations and related research
The study authors cautioned that their research was observational in nature. Because of this design, the findings do not prove a direct causal relationship between SSRI use and reduced cancer mortality, meaning further clinical investigation will be needed to confirm whether antidepressants directly improve survival outcomes.
The discovery comes alongside broader efforts to identify existing compounds that could aid in fighting cancer. Separate findings previously indicated that a natural compound derived from propolis, a resinous mixture produced by honeybees, can slow the development of colorectal cancer cells.
