Stress inner ear

Whale earwax has been studied to unlock the chemical history of the oceans^[1]. Forming as a plug, whale earwax has rings in it like a tree that map the history of their hormones – letting us know when they were under stress, for example – and the chemicals they were exposed to. This has allowed chemists to assess which substances such as drugs and fire retardants make their way into the environment and are potentially ecologically harmful.

More recently, researchers have begun studying the chemistry of earwax in humans^[2].

 

Anatomy of the ear. By BruceBlaus via Wikipedia Commons.

They have detected all sorts of hormones, but in particular are interested in cortisol levels.

Cortisol can be measured in the bloodstream, but it changes over incredibly short periods of time, so a stressful event – say, someone sticking a needle in your arm – can be sufficient to make your cortisol levels soar. It can also be measured in hair – but you need 3 cm of it, and not everyone has 3 cm of hair to cut off! Earwax, on the other hand, offers a longer term picture of cortisol levels, so it’s better at indicating whether levels are generally high or low. This could be useful for anxiety and depression diagnoses in mental health, which are currently extremely subjective.

However, there are a few problems with it. How does the earwax distinguish between someone with steady moderate cortisol levels, and someone with extreme peaks and troughs? And what does cortisol indicate? We know cortisol is related to stress, but we’re not exactly sure how it measures it, or whether it is indeed the best indicator! I guess we’ll find out...

References
why don't all references have links?

[1] Trumble, S. J., Norman, S. A., Crain, D. D., Mansouri, F., Winfield, Z. C., Sabin, R., ... & Usenko, S. (2018). Baleen whale cortisol levels reveal a physiological response to 20th century whaling. Nature communications, 9(1), 1-8.
[2] Herane-Vives, A., Ortega, L., Sandoval, R., Young, A. H., Cleare, A., Espinoza, S., ... & Benöhr, J. (2020). Measuring Earwax Cortisol Concentration using a non-stressful sampling method. Heliyon, 6(11), e05124.