Many of us have experienced the calming effects of lovely smells like jasmine or lavender. But a new study has shown that anxiety can cause the brain to transform neutral odors to negative ones, creating a “vicious cycle,” whereby stress is heightened.

Researchers from the University of Wisconsin-Madison used functional magnetic resonance imaging (fMRI) to look at the brains of a dozen volunteers who were shown disturbing pictures and texts in order to induce anxiety.

Before entering the MRI, the team, led by Professor Wen Li, had the volunteers rate a panel of neutral smells. After being exposed to screens displaying disturbing images, such as car crashes and war, the subjects were then asked to rate the same panel of neutral smells.

The results were published in the Journal of Neuroscience.

The researchers reported that after experiencing anxiety and stress, the human subjects assigned certain smells they had previously labeled neutral as negative.

Prof. Li says:

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 anxiety increases.”

During the MRI process, the researchers noticed that two independent circuits in the brain became “intimately intertwined under conditions of anxiety.” One circuit is associated with olfactory processing, the other is associated with emotion.

They note that under normal conditions, there is “limited crosstalk” between these two systems of the brain. But during induced anxiety, the researchers saw how the two circuits became a unified network.

Prof. Li explains that during “typical odor processing, it is usually just the olfactory system that gets activated.” However, during anxiety, “the emotional system becomes part of the olfactory processing stream,” she adds.

The team notes that the way anxiety or stress rewires the brain, causing neutral odors to change to negative ones, creates a “feedback loop,” which could increase distress and lead to clinical issues, such as anxiety or depression.

Until now, the way odors affect emotions – by biologically influencing the emotional centers of the human brain – has been largely unknown.

The researchers say their finding is important, as it might help others understand the way smell perception and anxiety can rewire the brain during stressful circumstances, fortifying negative emotions.

Prof. Li expands on this:

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.”

Medical News Today recently reported that a virtual hand could help treat anxiety and body image disorders.