Scientists in the US and China have found that the neurotransmitter serotonin, known for its role in regulating mood, may also influence the severity of tinnitus. The study found that increasing serotonin signaling in a specific brain circuit increased behaviors associated with the neurological disorder. This could help develop treatments for depression and anxiety without exacerbating tinnitis. The researchers used mice genetically altered to activate serotonin-releasing neurons in the dorsal raphe nucleus, an auditory region. They found that when these neurons were activated, serotonin could trigger a decrease in behavior. The results suggest that this brain circuit may play a direct role in generating the phantom sounds experienced by patients. The research also raises concerns about the potential harmful effects of antidepressant drugs on hearing.