Smells Become Stinkier When Anxiety Takes Hold
September 25, 2013

Smells Become Stinkier When Anxiety Takes Hold

Brett Smith for - Your Universe Online

Scientists are increasingly showing that our mental state can change our perceptions of the world around us and a new study in the Journal of Neuroscience found that people in a state of anxiety rate neutral smells lower than when they are relaxed.

"After anxiety induction, neutral smells become clearly negative," explained study author Wen Li, a professor of psychology at the University of Wisconsin-Madison. "People experiencing an increase in anxiety show a decrease in the perceived pleasantness of odors. It becomes more negative as anxiety increases."

In the study, researchers began by having twelve participants rate a panel of neutral smells. Next, participants underwent functional magnetic resonance imaging (fMRI) while display screens cycled through a series of disturbing pictures and texts. After this “anxiety induction” and the imaging process, subjects were once again asked again to rate the various neutral smells; most of the volunteers assigned negative responses to smells that they previously said were neutral.

The study researchers said their findings point to two distinct and usually independent circuits of the brain – one for olfactory processing, one for emotion – becoming intertwined as a result of anxiety.

"In typical odor processing, it is usually just the olfactory system that gets activated," Li said. "But when a person becomes anxious, the emotional system becomes part of the olfactory processing stream."

While these two systems of the brain are found next to each other, they typically don’t interact. However, anxiety was somehow able to create a unified network that bridged the two systems.

The results may be a step toward uncovering the biological mechanisms at work during periods of anxiety.

"We encounter anxiety and as a result we experience the world more negatively,” the scientists said. “The environment smells bad in the context of anxiety. It can become a vicious cycle, making one more susceptible to a clinical state of anxiety as the effects accumulate. It can potentially lead to a higher level of emotional disturbances with rising ambient sensory stress."

Another recently published study has made a similar connection – but in reverse. According to a report in Nature Neuroscience, researchers have used smell to invoke a sense of anxiety.

In the study, scientists at Northwestern University created the fear of a certain face by conditioning participants to link the face with a specific odor and a painful electric shock. After some time, the volunteers became fearful of the face, and the smell acted as a cue associated with that face.

The scientists then used the smell to decrease anxiety during participants' sleep as a way to enable patients to cope with their fear without the stress of full-on conscious terror.

The Northwestern research team said they have not tried this technique on peoples’ preexisting fears, but predicted it could be useful to create a connection between a phobia and a distinct odor. They added that the first type of patients in these trials would be those who already have an distinct odor associated with their fear — such as the smell of gunpowder.