Summary: Selective Serotonin Reuptake Inhibitors (SSRIs) are essential treatments for depression and anxiety for millions worldwide. New research, however, reveals that increased serotonin signaling can directly worsen or even trigger tinnitus — the persistent perception of ringing or buzzing in the ears.
By tracing a defined neural pathway that connects serotonin-producing neurons to the auditory system, scientists now explain why some patients experience a rise in tinnitus after beginning SSRI therapy.
Key Findings
- Circuit specificity: Researchers identified a distinct serotonergic circuit linking the dorsal raphe nucleus to the dorsal cochlear nucleus, providing a direct path by which serotonin influences auditory processing.
- Reversibility in models: In mice, turning off this specific serotonergic pathway substantially reduced tinnitus-like behaviors, indicating a promising target for future therapies.
- Clinical balance: The aim is not to abandon SSRIs but to refine treatments so they relieve psychiatric symptoms without unnecessarily activating auditory circuits that can produce tinnitus.
Source: Oregon Health & Science University
Overview: A new study published in the Proceedings of the National Academy of Sciences links serotonin signaling directly to tinnitus, shedding light on the neural mechanism behind medication-associated symptom flares.
Tinnitus is the perception of sound, such as ringing or buzzing, without an external source. It affects an estimated portion of the global population — in some studies up to 14% — and ranges from a mild nuisance to a condition that causes significant distress and anxiety.
Investigators from Oregon Health & Science University (OHSU) and Anhui University used mouse models to show that increasing serotonin levels in the brain produced behavioral changes consistent with tinnitus. Their work identifies a precise neuronal route by which serotonergic activity can cause excessive auditory-system activity and perceptual disturbances.
“People with tinnitus should work with their prescribing physician to achieve a balance: effective relief from depression or anxiety while keeping tinnitus from worsening,” said co-senior author Laurence Trussell, Ph.D., professor of otolaryngology at OHSU and a scientist in the OHSU Vollum Institute and Oregon Hearing Research Center. He emphasized that clinicians should take patient reports of medication-related increases in tinnitus seriously.
SSRIs increase serotonin levels to treat mood disorders, but the new findings show that the same neurotransmitter can, in certain brain circuits, drive hyperactivity linked to tinnitus. “We suspected serotonin played a role in tinnitus, but did not know how,” said co-author Zheng-Quan Tang, Ph.D., of Anhui University. “Using mice, we identified a serotonergic subpopulation in the dorsal raphe nucleus that projects directly to the dorsal cochlear nucleus. Activating this 5-HTDRN→DCN circuit produced tinnitus-like effects; inhibiting it substantially reduced those effects.”
Experimental approach and results
Building on earlier work, the team used viral-genetic tracing to map the circuit and employed optogenetics to precisely activate serotonin-producing neurons via light delivered through fiber optics. Activation increased spiking activity in fusiform cells of the dorsal cochlear nucleus — a pattern consistent with the electrical hyperactivity observed in tinnitus. In behavioral tests that measure altered auditory startle responses, mice exhibited signs consistent with perceiving phantom sounds.
Chemogenetic activation of the circuit produced tinnitus-related behaviors that were largely reversed by blocking 5-HT2A receptors. Noise exposure also raised serotonin levels in the dorsal cochlear nucleus and increased activity of the 5-HTDRN→DCN neurons in mice exhibiting noise-induced tinnitus behaviors. Crucially, chemogenetic inhibition of the same circuit significantly reduced noise-induced tinnitus-like behavior.
These data provide direct evidence that a discrete serotonergic projection from the dorsal raphe nucleus to the dorsal cochlear nucleus can generate the hyperactivity necessary for tinnitus perception and modulation.
Clinical implications
The study suggests a path forward for more targeted therapies: by developing drugs or interventions that modulate serotonin signaling in specific cells or brain regions, clinicians may be able to preserve the antidepressant benefits of SSRIs while minimizing their impact on auditory circuits. For patients, the immediate takeaway is not to discontinue medication but to consult with prescribing physicians about symptoms and possible treatment adjustments.
Funding: Trussell’s work was supported by the National Institutes of Health, award RO1DC004450. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.
Key Questions Answered:
A: No. Never stop prescribed medication without consulting your doctor. Tinnitus can be distressing, but untreated depression and anxiety carry serious risks. Talk with your clinician about adjusting the regimen, switching medications, or trying strategies that reduce auditory side effects while maintaining mental health benefits.
A: No. Tinnitus risk depends on multiple factors — genetic predisposition, history of loud noise exposure, and individual brain-circuit differences. This study clarifies a mechanism that explains why some people develop tinnitus with serotonin-elevating drugs, but it does not mean tinnitus will occur in all users.
A: This research is a significant advance. Identifying a discrete circuit responsible for tinnitus behavior opens the door to precision approaches — such as receptor-specific drugs or localized neuromodulation — that could reduce or eliminate tinnitus without compromising mood regulation. However, clinical translation will require further research and testing.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this psychopharmacology and auditory neuroscience research news
Author: Erik Robinson
Source: Oregon Health & Science University
Contact: Erik Robinson – Oregon Health & Science University
Image: The image is credited to 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
A discrete serotonergic circuit involved in the generation of tinnitus behavior
Although dysregulated serotonergic neurotransmission has been implicated in tinnitus, the precise neural-circuit mechanisms have remained unclear. This study investigated whether serotonergic input from the dorsal raphe nucleus (DRN) to the dorsal cochlear nucleus (DCN) — an auditory brain region whose hyperactivity associates with tinnitus — modulates behaviors in mice that are consistent with tinnitus.
Using neural tracing and viral-genetic tools, the authors defined a serotonergic subpopulation in the DRN that projects to the DCN (5-HTDRN→DCN neurons). Optogenetic activation of this circuit increased spiking in DCN fusiform cells, producing electrical hyperactivity consistent with tinnitus. Chemogenetic activation induced tinnitus-related behaviors that were largely reversed by blocking 5-HT2A receptors. Noise exposure raised 5-HT levels in the DCN and activated 5-HTDRN→DCN neurons in mice with noise-induced tinnitus. Importantly, chemogenetic inhibition of this pathway significantly ameliorated noise-induced tinnitus-like behavior.
These results demonstrate that activation of the 5-HTDRN→DCN circuit produces DCN hyperactivity sufficient for the perceptual generation and modulation of tinnitus. The findings provide direct evidence that DRN serotonergic neurons contribute to tinnitus pathophysiology and offer a clearer circuit-based framework for developing targeted treatments for sensory neurological disorders.