What Happens to Brain Connectivity Two Hours After Smelling Lavender?

Even two hours after participants had finished smelling lavender, differences were found in the way activity in their resting brains was connected. A 2025 study examined changes not only while the scent was being experienced, but also after exposure had ended.

However, participants’ self-reported relaxation did not improve significantly compared with an odorless control. An important feature of the study was that it tracked lingering brain-imaging changes separately from subjective effects.

Following 14 minutes of exposure for up to two hours

The participants were 14 healthy women aged 21–45 with a normal sense of smell. Each attended two visits approximately one week apart and experienced both the lavender and odorless-control conditions. The order was randomized, with half receiving the conditions in the reverse order.

Lavender essential oil was diluted to 50% in a solvent called isopropyl myristate. Three drops were placed on cotton attached to the MRI head coil, about 15–20 centimeters from the nose. Odorless saline was used as the control. It is worth keeping in mind that the control was not the same solvent used in the lavender preparation.

Scans were acquired before exposure, during the 14-minute exposure, immediately afterward, and one and two hours later. The immediate post-exposure scan began approximately three minutes after the cotton had been removed and the participant repositioned. No scent was presented again at the one- or two-hour time points.

Participants rested with their eyes closed, staying awake and allowing their thoughts to wander. The study measured resting brain activity rather than performance on a task. Between scans, they spent time in a separate quiet room.

What does brain connectivity mean?

Resting-state fMRI examines how signals in different brain regions fluctuate over time. The degree to which fluctuations in two regions are related is called functional connectivity. This does not measure an increase in the brain’s physical wiring or the direct reconnection of neurons.

The study focused on the salience network, which is involved in functions such as directing attention to important stimuli, and the default mode network, which is involved in internal thought and autobiographical memory, among other processes. These are abbreviated SAL and DMN, respectively. The authors examined how the relationship between the two networks changed during and after scent exposure.

Many connections decreased immediately afterward; increases appeared two hours later

The researchers first analyzed signal correlations using predefined brain regions as starting points. This method found no significant difference between lavender and the control.

They then used independent component analysis, which separates the data into patterns of shared fluctuation. This analysis found that changes associated with the presence or absence of scent differed across measurement time points.

During exposure, connectivity increased within the SAL and with some regions, while connectivity with areas such as the posterior cingulate cortex, a major DMN region, decreased. Immediately afterward, many regions showed reduced connectivity with the SAL, including regions within the DMN.

One hour later, decreases were confined to a small number of small regions. At two hours, increased connectivity with the SAL appeared in regions including parts of the DMN. The authors emphasize that the direction of these relationships changed over time, rather than remaining in the same state throughout.

Because the scan during exposure was longer than the others, the researchers also repeated the analysis without that time point and reported similar findings. However, the main-effect figure and accompanying text contain interchanged labels for time and scent. This article therefore focuses on the condition comparisons at individual time points.

Brain-imaging differences did not match the feeling of relaxation

Participants clearly perceived the lavender and, on average, rated it as pleasant. However, self-rated relaxation did not differ significantly between conditions, and the SRSI relaxation-state questionnaire showed no overall scent effect. There was also no difference in how freely participants felt able to let their thoughts wander.

Some relaxation scores are presented with identical values but labeled as pre-exposure in the table and during exposure in the text. The timing therefore remains uncertain, although both accounts report no significant improvement in subjective relaxation.

The authors discuss the possibility that the connections between networks at two hours may relate to flexible information processing. However, this study did not measure improvements in attention, memory performance, sleep, or health. Its design does not allow increased brain connectivity to be equated directly with improvement.

An exploratory study that selected its target after examining the results

An important point when reading this study is that, after independent component analysis, the researchers selected the SAL for detailed examination because it showed no difference before exposure but differences during and after exposure. Because the target was selected on the basis of a pattern of differences, this should be distinguished from an independent confirmatory experiment with a target specified in advance.

The study included only 14 women, one scent, one concentration, and one exposure duration. Menstrual status was not assessed. Changes in the scent’s intensity or quality as it evaporated from the cotton, and adaptation from continued exposure, were also not evaluated directly during scanning.

The authors frame this as a proof of concept showing that effects on the brain can be studied after scent exposure has ended. Important next steps are to specify the target networks and analytical methods in advance, and to test whether the findings replicate in men and with other scents, concentrations, and exposure durations.

Summary

In an experiment in which 14 women smelled lavender for 14 minutes, independent component analysis detected changes in relationships among resting-state brain networks for up to two hours afterward. Immediately after exposure, reduced connectivity between the SAL and other regions was common; at two hours, increased connectivity appeared with regions including parts of the DMN.

Meanwhile, the initial correlation analysis and subjective relaxation ratings showed no significant scent effect. The study demonstrates a way to trace the aftereffects of scent through changing brain connectivity. What those changes mean for everyday experience or functioning remains a question for future research.

Research context and disclosures: The paper states that no financial support was received for the research or publication. It also discloses that authors were employed by Brain Impact, LMR Naturals By IFF, IFF, and NIRx at the time of the study, and that one author served on Brain Impact’s scientific advisory board. The author-contributions section also lists funding acquisition among some authors’ roles, so the funding statement and corporate relationships need to be considered separately.

References

Kupers, R., et al. (2025). Long-lasting effects of lavender exposure on brain resting-state networks in healthy women. Frontiers in Neuroscience, 19, 1555922. Original study and open full text