New research suggests serotonin, a neurotransmitter tied to mood and commonly boosted by antidepressants, may also trigger or worsen tinnitus. Credit: Shutterstock Scientists have uncovered new evidence that serotonin, a brain chemical best known for helping regulate mood, may also worsen tinnitus, the persistent ringing or buzzing sound that affects millions of people worldwide. The research was published in the Proceedings of the National Academy of Sciences. Tinnitus can range from mildly