A commonly prescribed antidepressant may also strengthen the body’s defenses against cancer, according to new research from UCLA.

The study, published in Cell, showed that selective serotonin reuptake inhibitors (SSRIs) improved the cancer-fighting ability of T cells and reduced tumor growth in several types of cancers across both mouse and human tumor models.

“It turns out SSRIs don’t just make our brains happier; they also make our T cells happier — even while they’re fighting tumors,” said Dr. Lili Yang, senior author of the new study and a member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA. “These drugs have been widely and safely used to treat depression for decades, so repurposing them for cancer would be a lot easier than developing an entirely new therapy.”