Triggering Memories Through Scent Instead of Words Can Help Alleviate Depression

Kymberly Young, PhD

Credit: University of Pittsburgh, Department of Psychiatry

Scents can be powerful in recalling specific memories—even more so than word cues—and a new study found smelling a familiar scent can help individuals with depression by triggering positive memories.

“It was surprising to me that nobody thought to look at memory recall in depressed individuals using odor cues before,” said lead investigator Kymberly Young, PhD, associate professor of psychiatry at University of Pittsburgh School of Medicine, in the press release.

Young, a neuroscience researcher who studies autobiographical memories, discovered engaging the amygdala can help with memory recall. Since people with depression often struggle recalling specific memories, Young and colleagues wanted to see how smells differ from word cues on remembering specific events. In healthy people, scents trigger vivid memories, likely due to the fact they interact with the amygdala through nerve connections from the olfactory bulb, so the team aimed to find out if this was the same case for individuals with depression.

The cross-sectional study included 32 adults with major depressive disorder (MDD). Participants had a mean age of 30 years (range: 18 – 55 years), with 81.3% female; the sample included 65.6% of White participants, 21.8% of Asian Indian participants, and 12.5% of Black participants. Participants were excluded if they had a current or history of psychosis, bipolar I or bipolar II, major medical or neurological disorders, drug or alcohol abuse or dependence, current allergies, cold, COVID-19, or medical issues altering the sense of smell.

The team assessed specific autobiographical memory recall after both odor cues and word cues, given in a randomized, counterbalanced order. Before the experiment, participants had to refrain from smoking for ≥ 1 hour before and were told to avoid wearing any perfumes or cologne, as well as to not eat strong-smelling foods ≥ 2 hours before.

The team presented participants with several opaque glass vials filled with powerful familiar scents, such as oranges, ground coffee, shoe polish, and Vicks VapoRub. After smelling the vials with their eyes closed to avoid visual biases, participants were instructed to recall a specific memory—either good or bad—within 30 seconds. If they didn’t recall a memory by that time, it was recorded as a no memory trial.

Participants rated their retrieved memories on valence (positive, negative, no memory), arousal, vividness, and repetition (how often they think about the memory). Data was analyzed from January – June 2023.

Odors were correctly identified 29% of the time. Despite that, participants had stronger memory recall after smelling familiar odors than hearing word cues.

“This suggests that whether an individual is able to accurately identify an odor is independent from its ability to trigger AM recall,” investigators wrote.

Compared to word cues, memories with odor cues were more arousing (3.0 vs. 2.6; Cohen d, 1.28; P < .001), vivid (3.3 vs. 3.0; Cohen d, 0.67; P < .001), and slower (14.5 vs. 8.9; Cohen d, 1.18; P < .001).

Familiar scents also helped participants to recall a specific event, such as going to a coffee shop last Friday, rather than general memory which could be remembering they had been to coffee shops before, more than word cues (68.4% vs. 52.1%; Cohen d, 0.78; P < .001).

Moreover, healthy controls (80%) recalled fewer specific memories in response to words than scents (Cohen d, 1.18; P < .001), which could mean the results are overgeneralized. The team found the number of specific memories recalled due to familiar scents did not differ from the healthy control population mean (Cohen d, 0.26; P = .15).

Although participants had the choice of thinking about positive or negative memories, most participants were more likely to remember positive events with the familiar smells. Ultimately, scent triggers are more likely to effectively help individuals with depression rewire negative thought patterns—stimulating their brain with more positive memories.

Several limitations of the study the team highlighted was the small sample size and most of the sample being White females, although they point out this is representative of the population of patients with a major depressive disorder diagnosis.

Since the study only used low-tech, Young and colleagues are going begin more technologically advanced studies with a brain scanner to prove scent triggers benefit people with depression.

“If we improve memory, we can improve problem solving, emotion regulation and other functional problems that depressed individuals often experience,” Young said.

^References

1. ^{Leiker EK, Riley E, Barb S, et al. Recall of Autobiographical Memories Following Odor vs Verbal Cues Among Adults with Major Depressive Disorder. JAMA Netw Open. 2024;7(2):e2355958. Published 2024 Feb 5. doi:10.1001/jamanetworkopen.2023.55958}
2. ^{Are you Depressed? Scents Might Help, New Study Says. EurekAlert! February 13, 2024. https://www.eurekalert.org/news-releases/1034103. Accessed February 15, 2024.}