Tinnitus describes any sound that can be heard from inside the body rather than outside, and apparently affects 1 in 100 people! Although it is usually associated with ‘ringing in the ears’ other sounds such as grinding or whistling are sometimes heard (and indeed pulsatile tinnitus is used for sounds that seem to go in time with the person’s pulse!).
Several causes have been identified, including an earwax build-up, an infection in the middle ear, or another issue in the middle ear such as Ménière’s disease. There also seems to be a correlation between worsening tinnitus and situations of stress and anxiety.
I recently came across Dr Gillian Grafton’s research project, which looks specifically at the role of the neurotransmitter, serotonin, in the condition of tinnitus. As he says:
“Serotonin can affect cells through proteins on their surface called serotonin receptors. There are seven different kinds of these receptors and one of them, the 5-HT3 receptor is a calcium channel. This particular serotonin receptor is found in the auditory pathways in the brain and may have a role in the development of tinnitus so my track record of work on calcium channels has a direct relevance to this project.”
To go a little bit deeper:
“Serotonin has numerous roles including control of appetite, sleep, memory and learning, temperature regulation, and hormone function to name a few. The common factor is that serotonin allows certain types of nerve cells to talk to each other and to modify their behaviour. This is where the link with tinnitus comes in. It is possible that tinnitus arises in the auditory pathways in the brain (the chain of nerves that goes from the ear to various parts of the brain and which allows us to make sense of the sounds we hear). Nerves in this pathway talk to each other and once they have processed a sound they should quieten down. In tinnitus we think that they don’t – you might say that they’re listening out a little too hard and as a result might perceive sounds which really aren’t there at all. We think that serotonin, and particularly the 5-HT3 receptor, plays a role in this altered activity.”
The British Tinnitus Association has been a proponent of this line of research for a while, and based on findings that there is a clear link between serotonin and Tinnitus (Birmingham University and Buffalo University NYC), they hope for treatments to become more accessible.
There are other studies and anecdotal evidence worth reading, some suggesting that tinnitus is linked to high levels of serotonin, and others suggesting that serotonin pre-cursors are a useful treatment for sufferers of tinnitus.* Either way, hopefully there will be more clinical studies with proof soon, and sufferers of tinnitus will have more information on which to act.