When the "fight or flight" reaction occurs, your senses go on high alert. You become acutely aware of your surroundings, your energy increases, and your heart beats faster. During times of anxiety, your sense of smell also becomes more acute - and in some cases you may perceive odors as more negative than when you are calm.
Heightened sense of smell
When a dog senses a threat, he smells the air, trying to pinpoint the source of the threat. In much the same way, humans have a heightened sense of smell when anxious. Researchers at the University of Wisconsin-Madison completed a study in 2012 in which scientists examined the reactions of 14 young adults.
Each participant was exposed to several different odors, ranging from neutral to negative. Researchers asked participants to identify whether an odor was present and measured reactions using an MRI scanner. As anxiety levels rose, so did the ability of the participants to identify odors.
Smells become worse when under stress
In a follow-up study, Wen Li, a professor of psychology at the University of Wisconsin-Madison looked at how emotions have an impact on our sense of smell. Participants in this study were exposed to a set of neutral smells and asked to rate each one. They were then shown disturbing pictures, such as car crashes or images of war, and asked to rate the same odors again.
The researchers found that as anxiety levels increased, participants rated the same smells as more negative. "After anxiety induction, neutral smells become clearly negative. People experiencing an increase in anxiety show a decrease in the perceived pleasantness of odors. It becomes more negative as the anxiety increases," Li wrote.
When examining participants via MRI, the researchers noticed that two brain systems, one associated with sense of smell and one associated with emotion, reacted separately under calm conditions, but when anxiety was induced, these two systems merged, acting as one system. Our emotions, therefore, contribute to our sense of smell and our perception of different odors.
We know that different smells can invoke certain emotions. The smell of a favorite food may make us happy. The smell of Thanksgiving dinner might make you nostalgic. Different smells, such as lavender, can be relaxing for some people, while others scents, such as citrus, may invigorate you. But how and why this happens is unknown.
This recent study shows how anxiety can make you perceive smells as more negative and shows how anxiety actually rewires the brain - at least for a short period of time. Professor Li believes that this can lead to a cycle of anxiety and negativity. "We encounter anxiety and as a result we experience the world more negatively. 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."