The brain’s “feel good” chemical may be secretly fueling tinnitus

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 irritating to severely distressing.

For some people, the nonstop noise creates anxiety and disrupts daily life. Researchers estimate that as many as 14% of people globally experience the condition, with many cases considered severe. A team from Oregon Health & Science University and Anhui University in China studied mice and found that increasing serotonin levels in the brain also increased behaviors associated with tinnitus. The findings could have important implications for people living with tinnitus, especially those taking antidepressants that affect serotonin levels, said co-senior author Laurence Trussell, Ph.D., professor of otolaryngology in the OHSU School of Medicine and a scientist at the OHSU Vollum Institute and Oregon Hearing Research Center. "People with tinnitus should work with their prescribing physician to find a drug regimen that gives them a balance between relief of psychiatric symptoms like depression and anxiety, while minimizing the experience of tinnitus," Trussell said. "This study highlights the importance of clinicians recognizing and validating patient reports of medication-associated increases in tinnitus." The medications discussed in the study include selective serotonin reuptake inhibitors, commonly known as SSRIs. These antidepressants are widely prescribed for moderate to severe depression and anxiety because they raise serotonin levels in the brain. Researchers have long suspected serotonin played a role in tinnitus, but the exact mechanism remained unclear. "We've suspected that serotonin was involved in tinnitus, but we didn't really understand how," said co-author Zheng-Quan Tang, Ph.D., of Anhui University in China. "Now, using mice, we've found a specific brain circuit involving serotonin that goes straight to the auditory system, and found that it can induce tinnitus-like effects. When we turned that circuit off, we were able to ameliorate the tinnitus significantly. "This gives us a much clearer picture of what's going on in the brain -- and points toward new possibilities for treatment." Tang began the project while working as a postdoctoral scholar in Trussell's laboratory.

Key points

• For some people, the nonstop noise creates anxiety and disrupts daily life.
• Researchers estimate that as many as 14% of people globally experience the condition, with many cases considered severe.
• A team from Oregon Health & Science University and Anhui University in China studied mice and found that increasing serotonin levels in the brain also increased behaviors associated with tinnitus.
• The findings could have important implications for people living with tinnitus, especially those taking antidepressants that affect serotonin levels, said co-senior author Laurence Trussell, Ph.D.,…
• "People with tinnitus should work with their prescribing physician to find a drug regimen that gives them a balance between relief of psychiatric symptoms like depression and anxiety, while minimiz…