Familiar smells unlock memories in depressed people. Can olfactory therapy help those who suffer from this disease?

Study after study has shown that people with depression have trouble remembering specific things.

They may hear the word “party,” for example, and think, “I don’t get invited to parties often.” On the other hand, someone without depression might hear the word “party” and immediately remember a childhood birthday or a recent celebration at a friend’s house.

“It is not that depressed patients do not have memories, it is that have problems accessing them”explained Kymberly Young, associate professor of Psychiatry at the University of Pittsburgh.

Compared to other senses, such as sight or hearing, smells are more related to the way people process emotions or remember past events.Getty Images

Young may have found the key: A study published Tuesday in JAMA Network Open by Young and his team suggests that familiar smells could help unlock those memories.

In the study, people with depression evoked more specific memories when they were exposed to familiar odors – such as ground coffee or tobacco – than when they heard words that corresponded to those odors, such as “coffee” or “cigarette.”

The findings suggest that olfactory therapy could help people with depression avoid overthinking, he said.

Being able to recall specific memories “is associated with better problem-solving ability and better emotional regulation,” Young said.

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They participated in the study 32 adults with clinical depression. Participants were asked to sniff 24 odor samples from glass jars, which could be pleasant, neutral or unpleasant. The smells were orange, lavender, vanilla extract, cumin, whiskey, red wine, ketchup, cough syrup, disinfectant, and shoe polish.

They were then asked to share a specific memory from their life in response to those smells. The researchers performed the same exercise with 24 words that described each smell.

About 68% of the participants were able to evoke specific memories in response to the smells, while only 52% were able to do so after hearing the words aloud. Memories triggered by smells were also more vivid than those generated by words.

“It was more like reliving a memory” through a smell, Young explained.

Smells also produced more positive memories than words, although the result was not statistically significant, which means it could have been due to chance. Young said his research team is still trying to determine why there might be an association between certain smells and positive memories in people with depression.

Many studies have already identified a link between smell and memory in healthy people, said Vidya Kamath, a neuropsychologist at Johns Hopkins Medicine who was not involved in the new research.

“What this study expanded is the inclusion of depressive symptoms,” he said.

There is also a well-established relationship between the loss of the sense of smell and depression. A reduced sense of smell could increase the risk of depression, and late-onset depression in particular. In a survey of more than 300 people who reported having suffered some loss of smell due to COVID-19, 43% of participants reported feeling depressed.

“We think that decreased olfactory ability is associated with poor quality of life, poor hygiene, greater loneliness and weight loss. All of these things are ways in which we think that a bad sense of smell is related to depressive symptoms,” Kamath stressed.

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Research has also shown that people with depression are more likely to have a reduced sense of smell (known as olfactory loss), and that the symptoms of depression tend to get worse the more people’s sense of smell diminishes.

“It goes both ways. “There are people who have depression and then have olfactory loss, and then there are those who have olfactory loss that adds to the risk of depression,” said Michael Leon, professor emeritus of neurobiology and behavior at the University of California, Irvine, who was not involved in the study. the new study.

Leon explained that the olfactory system – the body structures, including the nose, that regulate smell – communicates directly with the limbic system, a region of the brain related to mood and memory. Consequently, smells are more closely related to how people process emotions or remember past events than other senses, such as sight or hearing.

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“The olfactory system is the only sensory system that has direct access to memory centers and the emotional centers of the brain. All other directions have to take secondary streets to get there,” Leon explained.

Olfactory therapy is already being studied as a means of treating depression, he added. A 2017 study found that aromatherapy – exposing people to fragrance oils – could help relieve symptoms of depression. Having people smell multiple odors on a regular basis probably has the same effect, Leon said, although the treatment has not yet been used on patients outside of a research setting.

Young’s study proposes a slightly different approach: In the future, he stated, smells could become a training tool to help people with depression better remember happy life events and tap into positive emotions. For example, someone might smell red wine and remember a fun time at a party.

However, Leon wondered if that approach would be more beneficial than others already being studied.

“People with depression have gotten better without having to go through this routine of remembering a smell at a party,” he declared, “it offers no advantage.”