Scientists Found the One Thing Stress Is Actually Good For

Stress is so unavoidable that we often have no choice but to laugh as it slowly and inevitably consumes us. Despite how often it might make us want to force a smile as we scream into the abyss, stress has some positive side effects, including how it releases the often-demonized hormone known as cortisol. Late-night infomercials blasting the newest pill or concoction to reduce cortisol production are missing something: the hormone they’re so eager to suppress has a hidden upside. It turns out that cortisol helps us hold on to memories.Not all stress is bad. When the brain detects a stressor, it triggers a short-term biological response known as fight-or-flight. The body can handle these episodes as long as they’re balanced by downtime, like a good night’s sleep. Chronic stress, which can drag on for months or years, is often damaging. But short bursts of stress can actually enhance memory, thanks to the cortisol they release. Scientists already knew cortisol was linked to memory, but now a team of Yale University researchers has dug deeper to learn why some memories fade while others live rent-free in our heads indefinitely.“Stress powerfully influences what we learn and remember, prioritizing encoding of emotionally arousing and stress-relevant memoranda at the expense of neutral content,” the researchers said in a study recently published in Science Advances. “These benefits are related to increased levels of stress-related hormones.”Emotional memories form in two steps. First the brain flags an event as emotionally arousing, then it encodes that event for long-term storage so it can be recalled later. Cortisol influences both steps. When something emotionally arousing happens under stress, the brain redirects resources toward processing it, which changes activity across its entire network of neurons. Previous studies have shown that cortisol can strengthen the effects of arousal-related neurons. Oddly, high arousal on its own can impair memory, but the same arousal paired with stress can enhance it. The brain also uses different networks for emotional memories than for neutral ones, and cortisol may change how the networks tied to memory and arousal interact.The Yale team set out to pin down exactly how cortisol affects the strength and staying power of memories. Participants took either a hydrocortisone pill (a pharmaceutical form of cortisol) or a placebo. They then viewed a series of potentially emotional images while a functional MRI (fMRI) scanner recorded their brain activity, and they rated how each image made them feel. Because fMRI tracks blood flow and oxygen levels to show which brain regions are most active and how that activity shifts over time, the researchers could see which images most strongly activated the regions involved in emotional reactions. The next day, participants were tested on how well they remembered each image. Then they repeated the entire experiment.To see how cortisol shapes memory, the researchers searched the scans for brain networks whose activity predicted either how emotionally aroused participants felt or which images they would later remember. Some networks predicted both. Cortisol had a consistent effect on both kinds of networks, but it affected each kind differently. While memories were being encoded, cortisol made the arousal-predicting networks stronger and more stable. The most stable were the frontoparietal network, which helps coordinate behavior, and the visual network. Cortisol also strengthened the connections between networks and enlarged the networks that predicted emotional arousal.Cortisol changed the brain’s memory networks, too. Under cortisol, both the networks that predicted memory and the networks that process emotion looked different than they did under placebo. Cortisol also increased the overlap between the networks that predicted memory and those that predicted arousal. In participants who took cortisol, the networks that forecast which images would be remembered also gave priority to storing emotionally arousing information. This hints at one way the brain adapts to stress.“Cortisol alters memory-predictive circuits, tuning them to prioritize encoding of emotionally arousing stimuli and bringing them closer to arousal-predictive circuits,” said the researchers. “Although further studies are needed to test this framework, these results provide key insights into the internetwork dynamics by which cortisol tunes successful emotional memory formation.”Elizabeth Rayne is a creature who writes. Her work has appeared in Popular Mechanics, Ars Technica, SYFY WIRE, Space.com, Live Science, Den of Geek, Forbidden Futures and Collective Tales. She lurks right outside New York City with her parrot, Lestat. When not writing, she can be found drawing, playing the piano or shapeshifting.