The Serotonin Tinnitus Severity Study That’s Making Doctors Rethink Antidepressants

People without tinnitus frequently fail to recognize the unique cruelty of the condition. It’s not as loud as an automobile alarm. It’s more subtle than that; a high-pitched ringing, occasionally a hiss, or a low throb that persists long after you go to sleep. It affects between 10% and 14% of people worldwide. It makes clinical sense that many of them also suffer from anxiety or depression, since the constant barrage of phantom noise would exhaust nearly everyone. Millions of those patients eventually take antidepressants, of course—SSRIs in particular. According to a recent study that was published in the Proceedings of the National Academy of Sciences, those prescriptions might have been subtly exacerbating the ringing.

Anhui University in China and Oregon Health & Science University in Portland are the sources of the study. The Portland connection is noteworthy because OHSU is located on a hill above the city and has a large campus where some truly rigorous neurological and auditory research is conducted, most of it hidden from the public. Zheng-Quan Tang, who had initiated this line of inquiry years prior as a postdoctoral scholar in Trussell’s own lab before returning to China, co-led the study with Laurence Trussell, an otolaryngology professor there and a scientist at the OHSU Vollum Institute. Long-term scientific collaboration like that usually yields more precise findings. The way they describe what they discovered gives you a sense of institutional memory.

Serotonin & Tinnitus — Key Study Information

Fundamentally, they discovered that serotonin travels directly from the dorsal raphe nucleus, a region of the brainstem where the neurotransmitter is produced, to the dorsal cochlear nucleus, an auditory processing center in the brain. Mice started acting in ways that strongly suggested they were hearing phantom sounds when researchers used fiber optic light to activate serotonin-releasing neurons in that circuit. Gaps of silence were inserted into a continuous sound in the most revealing test. Because their auditory system is already making noise, mice with tinnitus-like symptoms completely miss those silent intervals, while mice with normal hearing tend to startle less during them. The gaps were missed by the mice whose serotonin circuits were activated. Many of them.

What we can learn about human neurology from mouse models may be overstated, so it’s always advisable to exercise caution. However, the fact that this study is not isolated is what lends it credibility. For decades, patients and clinicians have reported that SSRIs exacerbate tinnitus. The mechanism was never present, but the anecdotal signal was. In contrast to another observational survey, Trussell and Tang have now sketched out what that mechanism might actually look like at the circuit level. The wiring is being pointed at by this.

Prescribing physicians face a genuine and likely uncomfortable challenge as a result. Among the most commonly prescribed medications worldwide are SSRIs like fluoxetine, sertraline, and paroxetine. They actually assist people. Previous studies, such as a 2010 study that was published in an audiology journal, found that paroxetine specifically decreased tinnitus distress in patients who also had anxiety and depression; the improvement in mood appeared to accompany the tinnitus relief. That is not insignificant. Trussell does not advocate for patients to cease taking antidepressants. Carefully, what he’s saying is that there’s a balance to be struck and that when patients report that their ears became louder after taking a new medication, doctors should take it seriously.

Reading the research and the institutional statements surrounding it gives the impression that medicine has been slow to validate the lived experience of tinnitus patients. The illness is infamously hard to quantify because it only causes a sound that the patient can hear, no external test results, and no visible damage. In the past, this invisibility has made it simple to ignore or treat as a side issue related to the mood disorder that brought the patient in. In a small but significant way, identifying a particular brain circuit that can replicate the condition under controlled conditions is an institutional acknowledgement.

It’s truly unclear what will happen next. According to Trussell, the results may lead to medications that specifically target serotonin, increasing it in areas related to mood regulation while excluding the auditory pathway. Theoretically, that kind of precision pharmacology is feasible, but there are many unsuccessful attempts between a mouse study and a clinical medication. However, compared to last week, the direction feels more definite now. The circuit has been located. Apparently, it can be turned off. Even though the translation to a pill on a pharmacy shelf is years away and far from guaranteed, those are helpful things to know.

That serves as both a small consolation and a reminder of how long it has taken to find these answers for the hundreds of millions of people who are thought to fall asleep every night to a sound that no one else in the room can hear.