Chronic stress: it’s not just bad for your stress ball budget. Left untreated, persistent stress can create a whole host of problems in the human body and brain. Beyond the muscle aches and migraines, there’s also anxiety, high blood pressure, a weakened immune system, and—of course—insomnia. Given the inherent dangers of not sleeping enough, it’s easy to see how unaddressed tension (even from past sources, as with PTSD) could become a vicious cycle. http://www.apa.org/helpcenter/understanding-chronic-stress.aspx
However, researchers at MIT have created a study illustrating a more surprising side effect of the high-stress life: risk-taking.
Let’s say you’re sitting in a meeting with your boss and your boss’s boss when you notice a mistake in your boss’s report. You could call it out, impressing your boss’s boss but alienating your direct superior. Or you could play it safe and say nothing, avoiding both the glory and the potential pitfall. Which way do you go? Contrary to what you might assume, those suffering from chronic stress might be more likely to take that plunge.
In 2015, MIT professor Ann Graybiel and her team identified what seems to be the brain circuit governing choices related to high-risk rewards.
Since then, Graybiel's team has delved into studying decision-making with the age-old tactic of screwing with lab rodents. First, the team trained rats to run a maze which branched towards both delicious chocolate milk and offputting bright light (the high-reward, high-risk scenario), and a weaker chocolate milk lit by a dimmer light. By inhibiting that single brain circuit, they could override a rat’s natural tendency away from risk and predispose them towards that sweeter, more dangerous alternative.
“Okay,” you say, “that’s a little creepy, but what does it have to do with stress?”
You see, in later studies, the team found another way to achieve similar results: stressing the rats out. In fact, the overwhelmed rats would continue to head towards that bright light even as the researchers gradually added more and more chocolate to the milk on the dimmer side. The healthy rats ran to the dimmer side in droves, but their stressed out comrades failed to re-evaluate their choices, remaining locked in to this dubious path.
The normal neural circuitry is disrupted, scientists theorize, with what’s called interneurons firing too late to calm the striosomes in the portion of the brain concerning habit, motivation, and reward reinforcement. The result? The striosomes run wild.
“Somehow this prior exposure to chronic stress controls the integration of good and bad,” Graybiel explained to MIT News. “It’s as though the animals had lost their ability to balance excitation and inhibition in order to settle on reasonable behavior.”
Some suggest that this could explain why chronic stress is also associated with greater degrees of substance abuse. The metaphorical chocolate of that short-term high suddenly outshines even the brightest and most threatening light.
There is some hope: by stimulating those interneurons, the researchers were able to inhibit the striosomes, and the rats gradually relearned their caution.
“This to us is extremely promising,” Graybiel said of her team’s findings, taking care to add a cautious note of her own: “but we are aware that so far these experiments are in rats and mice."
Still, something to consider the next time a work buddy suggests letting off a little steam at the casino…