Illustration: Kieran Blakey

The Nuance

Why the Stressed Brain Falls Back on Old Habits

In an effort to save energy and cognitive resources, the stressed brain prioritizes old habits and routines over purposeful, deliberative action

Distressed dogs tend to repeatedly lick their forelegs and paws. Happy and healthy dogs also do this, but stressed dogs do it more. In severe cases, they lick so frequently that they develop bald patches and skin ulcers.

Researchers have noticed similar anxiety-related behaviors in other animals — including humans. Many nervous or stressed-out people chew their nails, pick at their skin, or engage in other so-called body-focused repetitive behaviors (BFRBs) to the point of self-injury.

What explains BFRBs? The answer may be wrapped up in the way stress biases brain activity toward habitual thoughts and behaviors.

How stress encourages old habits

For a 2019 study in the journal Brain and Cognition, a team of Dutch researchers examined the brain’s response to stress. They found that as levels of the stress hormone cortisol increased following a threat or challenge, the activity in flexible, goal-directed brain systems tended to diminish. Meanwhile, activity in habit-related systems surged.

They concluded that in an effort to save energy and cognitive resources, the stressed brain prioritizes old habits and routines over purposeful, deliberative action. “Habits demand less cognitive effort, and thus become our default mode of behavior when stressed,” explains Tom Smeets, PhD, co-author of that study and a professor of social and behavioral sciences at Tilburg University in the Netherlands.

Other research teams have come to similar conclusions. A 2013 study in the Journal of Personality and Social Psychology found that stressful experiences are a drain on willpower and motivation. As a result, people fall into “automatic” and habitual patterns of behavior, the researchers wrote.

This isn’t necessarily a bad thing. While stress can push people toward heavy drinking, binge eating, or other bad habits, it can also reinforce beneficial routines, if they exist. A person who normally eats well and exercises is likely to stick to those healthy habits during times of stress, that study found.

These same rules apply in work-related contexts, where again the brain’s tendency to fall back on old routines can prove useful. “During stressful situations, using well-established habits and routines that have been successful in the past may be helpful,” says Lars Schwabe, PhD, head of cognitive psychology at the University of Hamburg in Germany. “Indeed, we can show that shifting to habit memory under stress may rescue performance.”

“Habits demand less cognitive effort, and thus become our default mode of behavior when stressed.”

All of this underscores the importance of establishing good habits, as well as the challenge of doing so during periods of stress.

But even if a person’s habits are initially helpful or healthy, some of Schwabe’s research, appearing in Trends in Cognitive Sciences, suggests that stress-related problems can surface.

Habit memory is “rigid and inflexible,” he says, and so it can be detrimental when changing circumstances demand a change in behavior. For example, someone who is heavily habituated to certain workflows or processes may find it difficult to pivot when a change of role or a new boss necessitates new approaches.

Schwabe also says that a strict adherence to personal routines and habits is a “hallmark feature” of a wide range of mental health conditions, including anxiety disorders, eating disorders, clinical depression, and obsessive-compulsive disorder. For people who are vulnerable to these conditions, the combination of stress and routine may promote the development of a pathology — whether it’s a BFRB like nail biting or a compulsion to exercise multiple times a day.

“If stress accelerates the shift from deliberate, flexible behavior to habitual, rigid responding — which occurs in all of us as we repeat a behavior very often — this may be one route through which stress biases our cognition in a way that increases the risk for a mental disorder,” Schwabe explains.

At the same time, an unbending adherence to routine may in some ways reinforce or heighten the brain’s stress-associated patterns of activity.

“If stress accelerates the shift from deliberate, flexible behavior to habitual, rigid responding… this may be one route through which stress biases our cognition in a way that increases the risk for a mental disorder.”

The antidote?

Stress and routine may turn out to be a destabilizing combination. Attempts to break up that duet — by reducing stress, switching up routines, and improving mental “flexibility” — may help people avoid the potential pitfalls, Schwabe says.

To reduce stress, Tilburg University’s Smeets says mindfulness meditation is one of several practices that may be helpful. There’s also evidence that mindfulness training may enhance cognitive flexibility, which is the brain’s ability to appropriately adjust thinking and behavior according to changing circumstances. Social interaction, physical activity, and novel experiences are also associated with enhanced cognitive flexibility, according to a 2019 study in the journal Frontiers in Behavioral Neuroscience.

Meanwhile, research has linked some activities to a drop in mental flexibility. Media multitasking is one of them, concludes a 2018 study from Texas A&M University. “The more an individual media multitasks” — for example, someone might text or check email while watching Netflix — “the more cognitive flexibility seems to be decayed,” says Jesus Lopez, first author of that study and a graduate researcher at Texas A&M.

The finding of Lopez’s study is in line with a larger body of evidence that has uncovered associations between some habit-forming and stress-inducing technologies — namely, email and social media — and reductions in cognitive flexibility and mental health. “Cognitive flexibility plays a huge role in preventing stress,” he says. “One of the main takeaways from my research is that you probably shouldn’t media multitask too often.”

Experts still have a lot to learn when it comes to the interaction between stress and habit. But what they’ve found so far suggests that the two may play off each other in ways that can be destabilizing.

I write about health and science. I live in Detroit with my wife and kids. I’m trying to learn German, but my progress so far is nicht gut.

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