Written by: Samantha E. De Alba
Edited by: Damaris K.
“Sometimes a certain smell will take me back to when I was young. How come I’m never able to identify where it comes from? I’d make a candle out of it if I ever found it...” (Twenty One Pilots, 2015)
These lyrics by Twenty One Pilots, an American musical duo, are from their song, appropriately titled, “Stressed Out” which captures the overwhelming pressures of adulthood. They describe the effects that childhood scents can have on one's feelings and memories, highlighting how olfaction (the act of smelling) is the link between scent and recollection. Many of us can relate to wanting to capture the smell that takes us back to cherished moments, at least for a fleeting second. Be it the smell of freshly baked cookies, the sharp tang of pool chlorine, the earthy aroma of wet grass or any other smell one might have linked to a positive emotion. Even if we don’t exactly recall when that association formed, our sense of smell is amazing that way— unlocking memories we may have long since forgotten.
But, the sense of smell is amazing in other ways too. Olfaction can offer insight into one’s brain health, prevent stress-induced neurodegeneration, and even detect Alzheimer’s. "How," you might ask? The answer is right under your nose (literally).
The Biology of Olfaction and Memory
Smelling involves the transport of particles to the brain's olfactory bulb, which is in charge of processing scents. After processing, the olfactory bulb relays information to the amygdala and hippocampus, the emotion and memory processing centers of the mind. (Walsh 2020). The proximity of these three regions helps explain how scents and memories become so closely intertwined. It is why certain smells transport us to moments we may have left long in the past. In fact, one’s sense of smell is one of the first senses to form, beginning in the first trimester of human development. Scent was the primary sense that guided us as infants exploring the world we were birthed into. With such heavy reliance, it is no wonder even the oldest of memories can be evoked by their scent (Nick, 2023).
But like memory, the sense of smell is an ability that fades with age. While less discussed, the loss of one's sense of smell coincides with that of memory loss, occurring at around 60 years of age (Dr. Takahashi 2023; Dr. Webber, as cited in Lang 2022).
Making Connections
Apart from being fascinating, this connection between smell and mind can also be life-saving. Recent research found that loss of smell may indicate an increased risk of Alzheimer's disease (Velayudhan et al., 2013b). A study by Velayudhan et al. compared the olfactory impairment of participants with and without Alzheimer's (AD). It concluded that participants with Alzheimer's had notably impaired olfaction compared to the control group and that within the participants with AD, the greater the progression of the disease the weaker their ability to smell.
While we are often mindful to report changes to our memory over time, it is just as vital to pay attention to shifts in our sense of smell. Studies like the one above support the idea that olfactory and cognitive functions can be used together to assess the severity of Alzheimer's disease. But, you may wonder: if memory can be maintained and strengthened over time, how can I help preserve my sense of smell? The old saying, “stop and smell the roses,” may be more than just a reminder to be present— it's also a way to mindfully exercise and strengthen our sense of smell.
Stress and Smell
However, Alzheimer's is not the only way one's sense of smell can be prematurely affected. Chronic (prolonged and excessive) stress has also been shown to affect one’s smelling abilities. “Chronic stress leads to long-term deficits in odor-driven behaviors that are critical for species survival and reproduction, and to neuroplastic changes in the nucleus of the lateral olfactory tract [which transmits
information about odors to other brain regions for processing]” (Masuo et al., 2021). Stress is associated with the release of cortisol to the body, which in excess can affect your cognitive abilities and mood. Common symptoms of chronic stress include poor memory, difficulty focusing, panic attacks, and heightened irritability, to name a few. When a person experiences stress for extended periods, the expression of brain-derived neurotrophic factors is weakened. especially in the hippocampus, leading to neurodegeneration and increased incidence of mental disorders (Kreinin et al., 2015 as cited in Masuo 2021).
Our sense of smell is so potent, that it can both induce and reduce stress. For example, while stress can be induced in numerous ways, unpleasant smells and smells with correlation to negative memories can also be enough to send one’s body into a panic. Although this may be lifesaving evolutionarily speaking, it can also be incredibly disturbing to experience over long periods. Inversely, other scents can combat the effects of stress.
Aromatherapy is a natural way to calm your central nervous system and mediate these effects, which dates back to around 3000 BC (Elshafie & Camele, 2017). Using personally comforting smells, like a familiar perfume, or scents shown to improve mood, such as citrus, can help to undo some of the negative effects of stress. The influence of aromatherapy is hard to deny, as it has been proven to work both behaviorally and biologically. When participants in a study were exposed to lavender and rosemary, their cortisol levels (as tested with their saliva) significantly decreased, thus confirming their protection from the effects of stress (Atsumi & Tonosaki, 2007).
Conclusion
The lyrics from Twenty One Pilots illustrate the profound connection between memory and odor, showcasing how a seemingly innocuous scent can transport one into days gone by, thereby offering comfort amidst life’s stresses. Considering this, our sense of smell is truly remarkable. It can regulate our nervous system, evoke past memories, calm, and even induce stress. It also has the ability to provide insight into the health of our brains, aiding in the detection of neurodegenerative diseases such as Alzheimer's. Let this be a reminder to ‘breathe in the moment,’ listen to our noses, and practice mindful smelling. to reduce stress and strengthen our olfactory system.
Works Cited
Atsumi, T., & Tonosaki, K. (2007). Smelling lavender and rosemary increases free radical scavenging activity and decreases cortisol level in saliva. Psychiatry Research, 150(1), 89–96. https://doi.org/10.1016/j.psychres.2005.12.012
Elshafie, H. S., & Camele, I. (2017). An overview of the biological effects of some Mediterranean essential oils on human health. BioMed Research International, 2017, 1–14. https://doi.org/10.1155/2017/9268468
Kreinin, A., Lisson, S., Nesher, E., Schneider, J., Bergman, J., Farhat, K., Farah, J., Lejbkowicz, F., Yadid, G., Raskin, L., Koman, I., & Pinhasov, A. (2015). Blood BDNF level is gender specific in severe depression. PLoS ONE, 10(5), e0127643. https://doi.org/10.1371/journal.pone.0127643
Masuo, Y., Satou, T., Takemoto, H., & Koike, K. (2021). Smell and Stress Response in the Brain: Review of the Connection between Chemistry and Neuropharmacology. Molecules, 26(9), 2571. https://doi.org/10.3390/molecules26092571
Nick. (2023, December 19). Why Baby’s Sense of Smell is Important | Pathways.org. Pathways.org. https://pathways.org/babys-sense-of-smell/
Velayudhan, L., Pritchard, M., Powell, J. F., Proitsi, P., & Lovestone, S. (2013). Smell identification function as a severity and progression marker in Alzheimer’s disease. International Psychogeriatrics, 25(7), 1157–1166. https://doi.org/10.1017/s1041610213000446
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