Q: Can scents pick me up from a sad mood?
A: There’s evidence that certain fragrances can influence mood, but it’s in its early stages. However, an interesting study was conducted on in China on depression in rats that might tell us something about fragrance, neurotransmitters, and emotions.
- A group of researchers from a medical school, a couple universities, and a hospital in Hefei, China got together to study a novel topic – depression and fragrance.
Specifically, is a pleasant fragrance capable of relieving the symptoms of depression?
However, the researchers wanted to really measure every possible variable in this study (you’ll see what I mean), so they had to do the study on a different mammal instead of humans. In this case, that meant rats.
It’s true that rats are not humans, and it’s possible we can’t draw direct conclusions from rat research to humans.
- On the other hand, researchers can do far more with rats than they can with humans – they can control the rats’ complete environment, measure a number of physiological factors, and stress them out to a stronger degree than they can with humans.
- Also, in rats and humans, the parts of the brain that sense smells highly overlap with the parts of the brain that process emotions (amygdala, hypothalamus, and hippocampus among others).
The researchers noted that olfaction (sense of smell) and emotions are strongly linked.
It’s possible that certain fragrances can help relieve emotional distress (like what you’d see in depression) without all the side effects of widely-used antidepressants.
This research was published in 2015 in the journal Psychiatry Research.
In this study, a number of rats were used as experimental subjects (male Sprague-Dawley rats, if you want to get specific).
They separated the rats into three groups:
- In one group, the rats went through a number of weekly, annoying (but not seriously harmful) stressors. These included a 5 minute swim in warm water, food and water deprivation, tail pinches, 5 minute swim in cool water, and a cage tilt (they tilted the rats’ cages which apparently is super annoying to rats). These stressors were administered randomly, 4 times within 4 weeks. It’s a hard knock life for lab rats.
- In the second group, a group of rats had their olfactory bulbs removed. This eliminated their sense of smell, which for rats is a huge bummer. You can see why they couldn’t do this on humans!
- Some rats were given no stress.
Then, rats in all the groups were randomly given treatments for the depression caused by the stress:
Some rats were given aromatherapy with an administration of vanilla scent.
Some rats were given fluoxetine (aka Prozac).
Some rats were given no treatment.
Both the annoying stresses AND the elimination of sense of smell resulted in depression-like symptoms in the rats. How do you measure depression in rats? Actually in some ways it’s quite similar to humans:
- Their appetites were screwed up – they lost their appetites and therefore lost weight (this often happens in humans with depression).
- For rats that went through the weekly stressors, a stress hormone called corticosterone significantly increased in their bloodstreams (not for the smell-loss group).
- The rats were placed in water to see how they swim, and “depressed” rats tend to give up and barely keep their heads above the water. This is similar to the helplessness observed in depressed humans.
- Finally, the neurotransmitters in the rats’ brains react similarly in depressed humans – there are reductions in serotonin and dopamine.
- Here’s where it gets interesting. What treatments were effective for the depression in the rats?
- Prozac reduced the helpless behavior in the depressed rats (good).
- Prozac also helped stressed rats keep their appetite up so they didn’t lose as much weight (good).
- Prozac also increased the neurotransmitters that are usually reduced in depression – serotonin and dopamine (good).
In other words, the anti-depressant worked as it is supposed to. Prozac reduces depression symptoms in rats (and humans).
- Vanilla also had a similar positive impact on stressed-out rats (on appetite, helplessness, and neurotransmitters), but ONLY on the rats that had their sense of smell.
- The reason they removed some of the rats’ sense of smell was to see if vanilla was somehow working in a way other than directly through smell (maybe it was absorbed into the bloodstream from the skin, for instance).
- But that wasn’t the case – vanilla only worked when the rats could smell it, which shows that the vanilla was an anti-depressant BECAUSE of the scent itself!
So what does all this tell us about vanilla and emotions?
It tells us that in stressed-out rats, vanilla scent worked to reduce depression symptoms in the same way that Prozac did.
This may actually tell us something about humans, because humans’ and rats’ brains are similar when it comes to emotions and senses of smell (those parts of the brain overlap).
This gives us definite evidence that a pleasant fragrance can reduce depression symptoms in rats, and possibly humans, too.
If true, this means there is a serious connection between fragrance and happiness!
Xu, J., Xu, H., Liu, Y., He, H., & Li, G. (2015). Vanillin-induced amelioration of depression-like behaviors in rats by modulating monoamine neurotransmitters in the brain. Psychiatry Research, 225, 509-514. Link: https://www.ncbi.nlm.nih.gov/pubmed/25595338