Scientists Discover Why Some Antidepressants May Worsen Tinnitus

New research suggests that serotonin, the brain chemical targeted by many antidepressants, may unexpectedly worsen tinnitus — the persistent ringing or buzzing in the ears. The findings, published in Proceedings of the National Academy of Sciences, help explain why some patients report louder tinnitus after starting antidepressant treatment.

Tinnitus affects an estimated 14% of people worldwide and can severely disrupt sleep, concentration and mental health. Although many factors can trigger the condition, including hearing loss and loud noise exposure, its exact biological mechanisms remain poorly understood, limiting treatment options.

Serotonin Connection To Tinnitus

A research team from Oregon Health & Science University and Anhui University in China focused on serotonin, a neurotransmitter best known for its role in mood regulation. Scientists investigated how increasing serotonin levels in mice affected brain circuits linked to hearing and tinnitus-like behavior.

Researchers discovered that stimulating serotonin-producing neurons activated regions of the auditory system and caused mice to behave as though they were hearing phantom sounds. The animals showed changes in an auditory startle test commonly used as a reliable laboratory indicator of tinnitus.

The findings support earlier clinical observations that some people develop new tinnitus symptoms or experience worsening tinnitus after beginning selective serotonin reuptake inhibitors (SSRIs). These medications — including sertraline and fluoxetine — work by increasing serotonin levels in the brain.

How The Brain Circuit Was Tested

To identify the exact neural pathway involved, scientists used optogenetics, a technique that uses light to control specific brain cells. By activating serotonin-producing neurons, researchers tracked how signals traveled to sound-processing regions of the brain.

When this pathway was activated, activity in auditory centers increased and tinnitus-like responses became stronger. Importantly, when researchers switched the same circuit off, tinnitus-like behavior dropped significantly, suggesting a direct role for this serotonin-linked pathway in generating phantom sounds.

Co-author Zheng-Quan Tang explained that the study offers a clearer understanding of serotonin’s broader effects beyond mood regulation. According to the findings, elevated serotonin may, in some cases, unintentionally increase auditory sensitivity or alter how the brain processes sound.

Implications For Antidepressant Use

Lead author Laurence Trussell stressed that patients should never stop antidepressants suddenly and should instead discuss any tinnitus changes with their doctor. For many individuals, the mental health benefits of SSRIs remain far greater than the potential auditory side effects.

The study also highlights the importance of taking medication-related tinnitus reports seriously, especially in patients who already have hearing problems or chronic tinnitus before starting antidepressants.

Researchers suggest future treatments could focus on increasing serotonin only in brain regions related to mood while avoiding the auditory system. Such targeted therapies may eventually preserve antidepressant benefits without worsening tinnitus symptoms.

The findings add to growing evidence that neurotransmitters involved in mood, anxiety and stress are closely connected to how the brain interprets sound. As tinnitus becomes increasingly common due to aging populations and widespread noise exposure, understanding these neural circuits may open new possibilities for treatment and relief.