Summary: Selective Serotonin Reuptake Inhibitors (SSRIs) help millions manage depression and anxiety, but new research shows elevated serotonin can directly worsen or even trigger tinnitus — the persistent perception of ringing or buzzing in the ears.
By tracing a precise neural pathway from serotonin-producing neurons to the auditory system, scientists have explained why some patients notice tinnitus worsening after starting serotonin-elevating medications.
Key Findings
- Circuit specificity: Researchers identified a distinct serotonergic pathway that connects directly to an auditory brain region implicated in tinnitus.
- Reversibility in a model: In mice, shutting down this specific serotonergic circuit markedly reduced tinnitus-like behaviors, revealing a potential therapeutic target.
- Clinical balance: The goal is not to abandon SSRIs, but to refine treatments so they relieve psychiatric symptoms without overstimulating auditory pathways.
Source: Oregon Health & Science University (OHSU)
New research published in the Proceedings of the National Academy of Sciences shows that serotonin — the same neurotransmitter targeted by many antidepressants — can directly influence the generation and modulation of tinnitus. Tinnitus affects an estimated portion of the global population and can range from a mild annoyance to a crippling condition that increases anxiety and interferes with daily life.
Researchers at Oregon Health & Science University and Anhui University used a mouse model to test how increased serotonin levels influence auditory processing and behavior associated with tinnitus. Their experiments show that activating a specific serotonergic projection raises activity in key auditory brain cells and produces behaviors consistent with tinnitus perception.
Laurence Trussell, Ph.D., professor of otolaryngology at the OHSU School of Medicine and co-senior author of the study, emphasized the clinical relevance: “People with tinnitus should work with their prescribing physician to find a drug regimen that balances relief from depression and anxiety while minimizing increases in tinnitus.” He added that clinicians should take patient reports of medication-associated tinnitus seriously.
Selective Serotonin Reuptake Inhibitors (SSRIs) raise serotonin levels and are widely used to treat moderate to severe depression and anxiety. While these drugs are effective for many patients, the study clarifies a biological mechanism that helps explain why a subset of people experience worsening tinnitus after starting or changing such medications.
Zheng-Quan Tang, Ph.D., co-author from Anhui University, described the discovery: “We found a specific brain circuit in mice that links serotonin-producing neurons to an auditory center and can induce tinnitus-like effects. When we turned that circuit off, the tinnitus-like symptoms were significantly reduced.” Tang began this work as a postdoctoral scholar in Trussell’s laboratory.
How the study was done
Building on earlier work, the team combined anatomical tracing, viral-genetic targeting, and optogenetics to selectively activate serotonin-producing neurons that project from the dorsal raphe nucleus (DRN) to the dorsal cochlear nucleus (DCN), an auditory hub previously linked to tinnitus. When these DRN→DCN serotonergic neurons were stimulated, fusiform cells in the DCN showed increased spiking activity consistent with tinnitus-like hyperactivity. Behavioral assays adapted from the auditory startle response indicated that mice perceived phantom sounds after circuit activation.
Importantly, chemogenetic activation of this circuit produced tinnitus-related behaviors that were largely reversed by blocking 5-HT2A receptors, and chemogenetic inhibition of the circuit reduced noise-induced tinnitus behaviors in mice. The researchers also observed that noise exposure elevated serotonin levels in the DCN and increased activity in the DRN→DCN neurons in animals with tinnitus-like behavior.
These results provide strong evidence that a discrete serotonergic input to the DCN can induce the neural hyperactivity sufficient to generate and modulate tinnitus, offering a mechanistic link between serotonin and auditory dysfunction.
Clinical implications
The findings point toward a path for developing more targeted treatments that preserve the mental health benefits of serotonin-based therapies while minimizing adverse effects on hearing. Future drugs or interventions that act selectively on specific cell types or brain regions could allow clinicians to maintain antidepressant efficacy without worsening tinnitus.
Funding: Trussell’s work was supported by the National Institutes of Health (award RO1DC004450). The content reflects the authors’ findings and conclusions and does not necessarily represent official NIH views.
Key Questions Answered:
A: No. Do not stop medication without consulting your doctor. Tinnitus is distressing, but treating depression and anxiety is essential. Discuss options with your clinician—adjusting dosage, switching medications, or exploring targeted therapies may help find the right balance.
A: No. Tinnitus has many causes including noise exposure and genetic factors. This study provides a mechanism explaining why some individuals experience tinnitus with serotonin-elevating medications, but it does not imply universal risk.
A: This work is a major step forward. Identifying an exact circuit involved in tinnitus generation creates opportunities to develop precision therapies that reduce tinnitus-related neural activity without compromising mood regulation.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The referenced journal paper was reviewed in full by editorial staff.
- Additional context and clarification were added to help readers understand the study’s significance.
About this psychopharmacology and auditory neuroscience research news
Author: Erik Robinson
Source: Oregon Health & Science University
Contact: Erik Robinson – Oregon Health & Science University
Image credit: Neuroscience News
Original Research: Closed access. “A discrete serotonergic circuit involved in the generation of tinnitus behavior” by Meng-Ting Yu et al., PNAS. DOI: 10.1073/pnas.2509692123
Abstract (summary)
Dysregulated serotonergic signaling has been linked to tinnitus, but the specific neural pathways were unclear. This study identifies a serotonergic subpopulation in the dorsal raphe nucleus that projects to the dorsal cochlear nucleus (the 5-HTDRN→DCN circuit). Optogenetic activation of this circuit increased spiking in DCN fusiform cells and produced tinnitus-like behavioral responses in mice. Chemogenetic activation induced tinnitus behaviors that were largely reversed by blocking 5-HT2A receptors, while chemogenetic inhibition reduced noise-induced tinnitus-related behavior. Noise exposure raised serotonin levels in the DCN and increased activity of 5-HTDRN→DCN neurons in mice displaying tinnitus-like behavior. These results demonstrate that activation of this specific serotonergic circuit can generate the neural hyperactivity associated with tinnitus and highlight a potential circuit-level target for future therapies.