Familiar scents unlock memories in people with depression. Could ‘smell therapy’ help patients?

Study after study has shown that people with depression have trouble recalling specific memories.

They might hear the word “party,” for instance, and think, “I don’t get invited to parties often.” By contrast, someone without depression could hear the word “party” and immediately recall a childhood birthday or recent celebration at a friend’s house.

“It’s not that depressed patients don’t have memories — it’s that they’re having trouble accessing them,” said Kymberly Young, an associate professor of psychiatry at the University of Pittsburgh.

Young may have found a key: A study published Tuesday in JAMA Network Open from her and her team suggests that familiar scents could help unlock those memories.

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

The findings suggest that smell therapy could help people with depression avoid overthinking, she said.

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

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

Participants were then asked to share a specific memory from their life in response to those cues. The researchers conducted the same exercise using 24 words that described each smell.

Around 68% of the participants could recall specific memories in response to the odors, whereas only 52% could recall specific memories after hearing words out loud. Memories triggered by smells were also more vivid than memories triggered by words.

“It was more like you were reliving that memory” through a smell, Young said.

Odors also produced more positive memories than words did, though the finding wasn’t statistically significant, meaning it could’ve been due to chance. Young said her research team is still trying to determine why there might be an association between certain smells and positive memories for people with depression.

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

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

There’s also a well-established link between losing one’s sense of smell and depression. A reduced sense of smell could increase the risk of depression, and late-in-life depression in particular. In a survey of more than 300 people who reported some smell loss due to Covid, 43% of participants said they felt depressed.

“We think about reduced smell ability being associated with poor quality of life, poor hygiene, increased loneliness, as well as weight loss. All of those things are pathways by which we think about poor smell being linked to depressive symptoms,” Kamath said.

Research has also shown that people with depression are more likely to have a reduced sense of smell (known as olfactory loss), and that depression symptoms 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 people who have olfactory loss that adds to the risk for depression,” said Michael Leon, professor emeritus of neurobiology and behavior at the University of California, Irvine, who wasn’t involved with the new study.

Leon said the olfactory system — the body structures, including the nose, that regulate smell — communicates directly with the limbic system, a brain region associated with mood and memory. As a result, smells are more strongly linked to how people process emotions or recall past events compared with other senses like sight or sound.

“The olfactory system is the only sensory system that has a direct, superhighway access to the memory centers of the brain and the emotional centers of the brain. All the other senses have to take the side streets to get there,” Leon said.

Smell therapy is already being studied as a means to treat depression, he added. A 2017 review found that aromatherapy — exposing people to fragrant essential oils — might help ease depression symptoms. Having people smell multiple odors on a regular basis likely has the same effect, Leon said, though the treatment hasn’t been given to patients outside of a research setting yet.

Young’s study proposes a slightly different approach: In the future, she said, odors could become a training tool to help people with depression get better at recalling positive life events and tapping into positive emotions. For instance, someone might smell red wine and remember a fun time at a party.

However, Leon questioned if that approach would be more beneficial than ones already being considered.

“People have already improved depression without going through this song and dance about remembering an odor at a party,” he said. “It doesn’t give you any advantage.”

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