The link between suicide and anosmia

Photo Cred: Robina Weermeijer/Unsplash

By Carolina Brooks, BA, IFMCP

Traumatic brain injury (TBI) can have consequences far beyond what many practitioners realize. The human sense of smell is reliant upon the proper functioning of the olfactory nerve, which meditates qualitative odor sensations and portions of the trigeminal nerve, which mediate somatosensory overtones of smells such as warmth, coolness, irritation, and sharpness. Smell receptors are located throughout the nasal respiratory epithelium, including regions of the olfactory neuroepithelium. Mucus plays a role in dispersing scents to underlying receptors. The olfactory nerve is the only cranial nerve directly exposed to the environment, and our only nose to brain conduit.

A recent documentary released in Germany about Michael Hutchence, lead singer of INXS, highlights the consequences of TBI. In 1992, Hutchence was in an accident while out with his girlfriend in Copenhagen. He was taken to the hospital but was discharged, with his aggressive behavior and slurred speech pointed to his alcohol intake.

According to the documentary, Hutchence spent a month on bed vomiting before he sought help, at which point he was diagnosed with TBI. The accident resulted in brain contusions and severed his olfactory nerve. Hutchence lost his sense of smell completely and 90 percent of his taste sensation. He suffered from headaches and depression, his gentle character changed, and he became erratic, obsessive, and aggressive. He became an addict. He died five years later in what was ruled a suicide. The coroner’s report mentioned two walnut-sized lesions on his frontal lobe.

The U.S. Brain Trauma Foundation released the first guidelines for managing severe head injuries in 1996, with football players and boxers assumed to be high risk due to repeated injuries. Today, there remains a lack of understanding and connection between TBI, consequential changes in behavior, and other symptoms.

According to the National Institute on Deafness and Other Communicable Disorders (NIDCD), three percent of Americans suffer from anosmia or severe hyposmia.

Anosmia can be due to various reasons, such as chronic rhinosinusitis, which blocks the nose and creates pressure, TBI, viruses, oral appliances such as dentures, dental procedures, oral infections, Bell’s palsy, and neurodegenerative diseases. Radiation treatment of the head and neck, certain cancers or lesions associated with taste pathways, cigarette smoking, and immunodeficiency syndrome may also play a role. Anosmia can be specific, or odor perception can be distorted.

Toxic chemical exposures such as benzene, chlorine, formaldehyde, paint solvents, and sulfuric acid may drive anosmia, along with industrial agent exposures such as nickel, lead, cadmium, and silicon dioxide, indicating that those in professions using toxic metals and chemicals may be more at risk. Cocaine use can also cause anosmia due to its intranasal ingestion.

From a nutritional perspective, nutritional deficiencies such as zinc, copper, vitamins A, vitamin B6, and vitamin B12 are known drivers of anosmia. Some antibiotics, anticonvulsants, and antidepressants are known to alter smell and taste function.

The American Medical Association does not consider anosmia or ageusia as significant measures of value of life’s worth and as such does not compensate well for work-related injury cases in which this occurs.

The olfactory nerve allows us to be aware of dangers in the environment, stimulates appetite, triggers digestive secretions, enhanced sense of taste and, provides awareness of foods to avoid eating in case they are rotten.

Smells also play a role in memory creation and recall and allow us to interact with the outside world. Dopaminergic brain receptors are activated by food odors, which makes it easier for us to understand why Hutchence, having experienced anosmia, abused substances.

With lack of appetite stimulation comes weight loss. Many people who suffer anosmia often talk about the worry and stress around personal hygiene perception, accidents at home that occur, particularly when cooking, and lack of joy around food. Adapting meals to increase texture variations can help.

A 2014 study in the journal PLOS One found that the strength of a person’s ability to identify odors is a strong predictor of death, and when sense of smell fades, risk of dying within the next five years is over three times higher regardless of mental illness or other health variables. Additionally, the study hypothesizes anosmia may be an indicator of cumulative toxic exposures, and the inability of olfactory stem cells to regenerate indicate that the body’s overall ability to repair itself, has been compromised.

Another study in the journal Stem Cells discussed the differences in olfactory mucosa stem cells from patients with schizophrenia, Parkinson’s disease and familial dysautonomia, with disease-specific changes in gene expression and cell function including faster proliferation, altered cell migration, shorter cell cycle, and oxidative stress. Studies have also demonstrated that acquired anosmia often leads to anxiety and depression, including a 2016 review in the journal Chemical Senses, which discussed the shared neuronal connections between the olfactory bulb, the limbic system, and the reciprocal relationship that exists between depression and olfaction. Primary depression patients experiencing reduced ability to smell while patients suffering primary olfactory dysfunction experience a worsening of depressive symptoms as their olfactory function worsens.

Finally, a 2018 Danish study in the Journal of the American Medical Association discovered that traumatic brain injury sufferers will experience a nearly double suicide risk. The study talks about how 25 percent of patients may experience chronic neuropsychiatric symptoms such as depression and anxiety for years after the initial injury, and the increase in inflammation and damage to blood vessels disrupt normal function and increase the risk for mental health disorders and suicide.

Medical practitioners need to be made aware of the links between suicide and the severity of traumatic brain injury, and the links between anosmia and depression. Had Hutchence been offered immediate treatment, and appropriate implementation of early psychiatric support, there is a chance he might not have taken his own life.

References

Mackay-Sim, A. (2012) Concise review: Patient-derived olfactory stem cells: new models for brain diseases. Stem Cells. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/22961669

Pinto, J.M., Wroblewski, K.E., Kern, D.W., Schumm, L.P., McClinktock, M.K. (2014) Olfactory dysfunction predicts 5-year mortality in older adults. PLOS One. Retrieved from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0107541 

Kohli, P.K., Soler, Z.M., Nguyen, S.A., Muus, J.S., Schlosser, R.J. (2016) The association between olfaction and depression: a systematic review. Chemical Senses. Jul; 41(6): 479-486.  Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4918728/

Madsen, T., Erlangsen, A., Orlovsa, S., Mofaddy, R., Nordentoft, M., Benros, M. E. (2018) Association Between Traumatic Brain Injury and Risk of Suicide. Journal of the American Medical Association. Retrieved from: https://jamanetwork.com/journals/jama/article-abstract/2697009