Folk medicine has used plant-derived aromatic compounds to treat anxiety for years. Rosemary and lavender, famous for their relaxing scents, aren't just planted in garden borders — they're added to personal care products, from bath bombs to body wash to fabric softener.
Now a Japanese study offers some solid evidence to back up claims for the anxiolytic or anti-anxiety effects of lavender. When linalool, a type of alcohol found in lavender extract, is smelled through the nose — as opposed to breathed in through the lungs — it reduces anxiety. Establishing the mechanism of action for linalool is an important step toward its clinical use in humans.
“In folk medicine, it has long been believed that odorous compounds derived from plant compounds can relieve anxiety,” Hideki Kashiwadani, a co-author on the study, said in a statement. Although many studies confirm the relaxing effects of linalool, he said, they were not designed to determine exactly how the compound works.
Scientists assumed linalool was absorbed into the bloodstream through the airways, and would then affect the gamma-aminobutyric acid (GABAergic) receptors in the brain, the same cell receptors targeted by drugs like Valium that are prescribed for anxiety.
Establishing the mechanism of action for linalool is an important step toward its clinical use in humans.
Kashiwadani and his team observed the behavior of mice exposed to linalool vapor to determine if the odor triggers a relaxation response by stimulating the olfactory (odor-sensitive) nerve cells in the nose. They found the odor of linalool had an anxiolytic effect in normal mice, but linalool vapor did not affect movement in the mice.
However, no effect was seen in mice who had their olfactory neurons destroyed, suggesting that linalool vapor exerted its relaxing effect by triggering signals in their olfactory neurons.
The anti-anxiety response in normal mice also disappeared when their olfactory neurons were blocked by a compound that completely dampens the benzodiazepine-sensitive GABAergic receptors. “Taken together, our findings suggest linalool does not act directly on the GABAergic receptors, like benzodiazepines do, but must activate them via the olfactory neurons in the nose to exert its relaxing effects,” explained Kashiwandi, a senior assistant professor of physiology at Kagoshima University.
The relaxation seen in normal mice fed or injected with linalool may be due to the smell of the compound in their exhaled breath. Future studies are needed to establish the doses and safety of linalool when it is administered via different routes, but the researchers hope their work could eventually lead to the use of linalool in recovery rooms to treat preoperative anxiety as well as anxiety disorders.
The study is published in Frontiers in Behavioral Neuroscience.