Why rats can teach us a lot about relieving stress

A stress-free life is hard to come by. And thanks to the pandemic, climate change and the high cost of living, people are feeling anxious and mental health concerns have been on the rise in recent years.

Scientists are always searching for ways to improve our resilience to stress. Some have turned to the humble rat for help.

Rat City, a documentary from The Nature of Things, takes viewers on a wild ride into the secret world of the brown rat, and how it may be able to teach us a few lessons about managing our stress.

Chronic stress has physical and mental impacts

It turns out rats and humans have a pretty similar response to stress. Behavioural neuroscientist Kelly Lambert runs a lab at the University of Richmond in Virginia using domesticated brown rats.

"Their brains have generally all the same parts ours do," said Lambert. "They have all the same neurochemicals, so it's a good place to start."

When humans are stressed, our bodies are flooded with a stress hormone cortisol. In rats, that hormone is corticosterone. It's a natural defense we share when faced with danger, triggering a classic fight-or-flight response. That's helpful when we're running away from a bear, but if we're constantly stressed out, it can take a toll on our physical and mental health.

Chronic stress can increase our risk of developing Type 2 diabetes, high blood pressure and heart disease, as well as mental health disorders such as depression and anxiety. "If we interpret everything as being incredibly threatening, we're going to wear the system down," Lambert said. "Stress is incredibly important, so we need to learn more about that."

Effort-based rewards may improve our mental state

Our brains are swimming in neurochemicals like dopamine and serotonin, which have a considerable impact on our behaviour and mood. Lambert wondered if it would be possible to alter the structure and chemistry of the brain by changing behaviour and to improve resilience to stress in the process.

Lambert and her team divided their rats into two groups and gave them their favourite treat: Fruit Loops cereal. The only difference? One group had to work for the Fruit Loops, digging through nesting material to find the reward. The second group didn't have to lift a paw to receive their sugary snack.

When the two groups were then tested with a new experience, like swimming, the "worker rats" were bolder and more explorative. They showed more ability to cope as well as neuroplasticity in part, the brain's ability to adapt to a changing world.

The scientists discovered the worker rats also had lower levels of stress hormones: taking an active, rewarding role in their environment helped their brains.

The team wondered if activities with "effort-based rewards" like knitting, gardening, baking or woodworking might have the same effect in humans, increasing dopamine while reducing stress hormones.

Putting rats in the driver's seat literally

Like us, rats get stressed when they have no control over their lives. Lambert wanted to see what would happen if she put rats in the driver's seat literally.

She put her lab rats in a pint-sized driving school, where they trained in tiny plastic cars called ROVs, or rodent-operated vehicles. For their efforts, the rats were rewarded with Fruit Loops.

"One thing that we've learned about stress is unpredictability, uncertainty that leads to stress in our lives," said Lambert. "When you make a rat's world unpredictable especially if they're negative, unpredictable things that also leads to chronic stress. One way of giving them back a little bit of control is to give them opportunities to engage with the world around them."

Not only did the driving reduce the rats' levels of corticosterone, but it also increased a hormone called dehydroepiandrosterone (DHEA), which boosts resilience to stress. The more the rats drove their cars, the higher the ratio of DHEA to corticosterone. "We think it's providing a buffer against the toxicity of this cortisol," said Lambert.

"Humans, maybe if you're stressed out, [go] for a drive," she said. "That's something you can control when you can't control the other stuff going on."

Why scientists taught these rats to drive tiny cars

2 years ago

Duration 2:11

Neuroscientist Kelly Lambert studies stress, and has found that rats become more chilled out and resilient to stress if you give them control. So she taught them how to drive. Watch Rat City on CBC Gem.

Having control improves our ability to cope with stress

Actively engaging with our world likely helps our brain health. And that may be more important than ever before, noted Lambert. "In a world with all of our advanced technology, where we're more likely to not be so engaged with the physical world we're engaged with the electronic or digital world I'm not sure that's the same engagement for the brain," she said. "So we need to be careful about what we're evolving into. And the rats and some of the other neuroscience research may give us some clues about what is OK and what we should be cautious about."

Lambert and her team continue to work in this emerging field of brain research with her rodent colleagues, exploring the behaviours that allow brains to better handle stress. One day, this work may lead to treatments for mental health conditions such as anxiety and depression.

So maybe it's time to pick up a hobby, learn a new skill, or take a spin in the country. We may not get any Fruit Loops for our efforts, but we'll likely be more relaxed.

Watch Rat City on The Nature of Things.