Between climate change, the COVID-19 pandemic and wide-ranging political unrest, it is easy to feel overwhelmed by stress.

That is not true for everyone, however. While stress can lead some people to become anxious and depressed about world events, others seem more resilient, better able to compartmentalize those concerns and move on.

The findings suggest that resilience can be learned and possibly reinforced.

Mice are similar. Some are persistent in the face of stress; others, not. Having noticed that some mice in the lab would defend themselves when confronted with a larger, more aggressive mouse, a team at Princeton University decided to explore this idea of resilience further, “They’d turn back towards the aggressor, they’d throw their paws out, and they would not give up,” Lindsay Willmore, lead author on the paper, said. “I thought, ‘There must be something going on in these guys’ brains that could be the key to resilience.’”

What Willmore and her Princeton Neuroscience Institute colleagues discovered suggests that resilience can be learned and possibly reinforced. When placed in a cage with a larger, more aggressive mouse, a smaller mouse who displayed defensive behavior was more likely to be resilient after the stressful encounter. Stimulating dopaminergic neuron activity reinforced resilient behavior when the smaller mouse fought back. Stimulating dopamine when the mice avoided their aggressor did not reinforce resilience.

The researchers found this particularly interesting. “What was really cool to me is that an animal that is not just fighting back, but is rewarded for fighting back, is the one that becomes resilient,” Willmore said. The mice that ran away from their aggressors and did not try to defend themselves displayed behaviors characteristic of depression, such as social avoidance.

The mice were paired in cages for 10 days. Resilience was measured by monitoring the smaller mice’s behavior when they were subject to attacks from their larger cage mates. Afterward, the paired mice were kept in the same cage, but were separated by a mesh wall. “The stress experience itself is not just getting beat up, but having to live with the guy who beat you up behind a barrier for the rest of the day,” explained co-author, Annegret Falkner, an assistant professor of neuroscience at Princeton.

The researchers hope that in the future, their findings can be applied to human health. “We need to think about ways to help people who seem to be susceptible cope with the stresses of the world,” Falkner added.

Wearable technology such as smart watches, for example, can give feedback in real time about healthy habits that encourage resilience. “Information about dynamic interactions with the environment will be useful for tracking habits that might be helpful or harmful,” said Willmore, who received her PhD from Princeton in 2022.

The study is published in Nature.