Revolutionizing depression diagnosis: earwax analysis for cortisol and beyond

Depression is a psychiatric disorder that profoundly affects the mental well-being of individuals, leading to detachment from social and professional life. Approximately 280 million people worldwide suffer from depression, resulting in about 700,000 suicides each year, making it the fourth leading cause of death among the younger population [1].

Stress is closely associated with depression, as recent research has revealed a molecular mechanism in which elevated cortisol levels induced by stress lead to increased extracellular cortisol. This results in the downregulation of serotonin transporters and impaired neuronal transmission across the synaptic cleft, contributing to depression even in resting conditions or during nerve stimulation [2].

Cortisol, commonly known as the body's stress hormone, enables the body to remain active and alert in stressful situations [3]. Traditional methods of measuring depression included the use of questionnaires and scales such as the Hamilton Depression Rating Scale [4], as well as the measurement of cortisol levels in blood, urine, or saliva through immunoassays (which are bioanalytical methods where the quantitation of the analyte depends on the reaction of an antigen and an antibody [5]). However, these methods are unreliable. Serum cortisol assays measuring total cortisol can yield inaccurate results in patients with irregular serum protein concentrations. The absence of a standardized reference range and standardized assays limits the use of salivary cortisol. Additionally, hair cortisol concentrations can be influenced by the presence of baldness and the lack of standardized reporting units, posing challenges for interpretation [6,7].

In a significant development, a new method for measuring cortisol levels and potentially diagnosing depression has been discovered through the extraction of cerumen (earwax) using a newly developed device by TREARS under the guidance of Dr Herane-Vives [8]. Cerumen is a waxy substance secreted by ceruminous apocrine sweat glands in the external ear canal, composed of a mixture of fatty material, sweat secretions, enzymes and hormones [9]. Dr Herane-Vives' study highlighted that previous methods of cortisol measurement were stress-inducing, leading to fluctuations in cortisol levels. However, the new earwax device utilizes a non-stressful self-sampling method, resembling earbuds or a cotton swab, with a plastic body and a removable cellulose sponge tip infused with a mineral oil solution of magnesium chloride (MgCl₂). The design of this device ensures ear safety, as it includes a brake mechanism that prevents it from crossing beyond the external auditory canal [10].

The methodology employed in the study involved the extraction of earwax from both ears of 37 control subjects. After 1 month, the researcher extracted earwax from the left ear using a Reiner-Alexander syringe while employing the new device for the right ear. Participants also provided a strand of hair to represent cortisol levels over the previous month and a serum sample to account for systemic stressors' effects on cortisol levels. A comparison of cortisol concentrations in earwax (ECC), hair (HCC) and serum (SCC) indicated that confounding factors did not influence the sample from the right ear (right-ECC) (all p > 0.05). However, the cortisol concentrations in the left ear sample (left-ECC) were higher than in the right ear (p = 0.03). Furthermore, a Pearson correlation analysis revealed a moderate correlation between cortisol concentrations in the right earwax and hair samples (r = 0.39, p = 0.03). Serum samples exhibited the highest cortisol levels, while hair samples had the lowest concentrations [10].

This device eliminates biases associated with variations in cortisol levels. It simplifies the collection of earwax samples, making it a more practical and accessible option for cortisol analysis at home compared with other laboratory-based methods. The device's precision can aid in rapidly diagnosing other cortisol-related conditions, such as Addison's and Cushing's syndrome. A recent study has made a significant discovery by demonstrating the isolation of hepatitis B through cerumen, highlighting the clinical application potential of this device for a wide range of diagnostic purposes [11]. This innovative methodology establishes a low-cost and convenient technique that can benefit the general population.

Depression, a highly stigmatized disorder, has the potential to profoundly impact an individual's ability to contribute to society, creating personal and professional challenges and transforming into a liability. However, this device offers a glimmer of hope by enabling the early and cost-effective identification of depression, allowing for timely management before it worsens and inflicts additional financial and emotional distress upon the patient [12]. Moreover, with its ability to diagnose other significant pathologies, including the measurement of cortisol levels, this device can assist patients in effectively managing their disorders. Introducing this measurement method holds the promise of uncovering new diagnostic approaches for assessing hormones and enzymes present in earwax, ultimately leading to improved medical care and outcomes.

Financial disclosure

The authors have no financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Competing interests disclosure

The authors have no competing interests or relevant affiliations with any organization or entity with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, stock ownership or options and expert testimony.

Writing disclosure

No writing assistance was utilized in the production of this manuscript.