Anxiety disorders are the most common type of mental disorders in the U.S. But a simple diagnosis of generalized anxiety disorder may not capture the specifics of what bothers some people. A subgroup of anxiety sufferers may experience extreme distress when confronting the inherent uncertainties that turn up in any life circumstance, whether helping a relative with a severe illness or choosing a new route to work that is safe and easy to navigate.

Such people may respond to their feelings by leaving nothing to chance. At work, they appear polished and prepared when giving a presentation because they consider every question that could be posed by colleagues beforehand and memorize possible answers in the days leading up to a meeting. Still, all of the prep work may do little to relieve feelings of painful anxiety.

Psychologists, though, are learning new ways to treat these sufferers, who can be identified through their answers to a psychological measurement known as the intolerance of uncertainty scale (IUS). Patients can then benefit from specialized treatment.

These patients are typical of the ones psychologist Keith Bredemeier sees at the University of Pennsylvania’s Center for the Treatment and Study of Anxiety. When encountering patients with a high score on the IUS, Bredemeier may explicitly target enhancing their comfort levels with life’s unpredictability as a treatment goal. Since therapy is adapted to patients' salient personality traits, treatment for uncertainty distress may be added to their treatment plans just as treatments for eating disorders, for example, may focus on clients' perfectionism. And therapy for obsessive-compulsive disorder may concentrate on patients' inflated sense of responsibility. 

Difficulty dealing with uncertainty was first identified in the early 1990s as a distinguishable personality trait. It is one we all have to some degree, but many of us have it at an elevated level. Like perfectionism or rigidity, it is really a predisposition, not a diagnosable disorder. People who have high levels of perfectionism, for example, are at greater risk of developing anorexia. And someone with a high level of intolerance of uncertainty (IU) may end up developing an anxiety disorder.

To cope, a person may live along a narrow, predictable track. Everything may seem fine to them on the surface, but their risk for developing anxiety, depression or emotional distress is higher—especially if something such as, say, a pandemic wreaks havoc on a carefully planned life.

In the decades since the IUS was developed, researchers have found it useful for understanding why some patients are anxious, devising targeted therapies and assessing a patient’s progress. In psychology labs, investigators have probed how uncertainty affects people’s brain and behavior. Clinicians have used the concept to develop programs that teach parents of autistic children strategies to help their children better tolerate uncertainty. And tourism specialists have delved into which clients might prefer guided tours instead of unguided ones. Most of all, because the pandemic blew away a sense of predictability in everyday life, the concept has sparked an explosion of research globally to find out how those who typically feel this type of distress are faring in these uncertain times and what might be done to help them.

It Began with a Hunch

In the 1990s Mark Freeston and Michel Dugas were part of a team at Laval University in Quebec looking into generalized anxiety disorder. The focus in the field was on worry. The thinking at the time “was that worry was some form of problem-solving gone wrong or a problem-solving deficit,” notes Freeston, who is now at Newcastle University in England. But Freeston and his colleagues saw something different in their patients’ behavior. “They knew how to solve problems, but something was getting in the way,” he says. The team hypothesized that anxious people might have a negative reaction to uncertainty. Following a “clinical hunch,” he says, the group developed the IUS and tested it out.

When filling out this questionnaire, people indicated how they might react to statements such as “Unforeseen events upset me greatly” and “It frustrates me not having all the information I need.” The scale accurately assessed subjects’ reactions—cognitive, emotional and behavioral—to uncertain situations in which they felt they did not know vital information or could not control the future.

Evolution and Fear of the Unknown

For humans and other animals, fear of uncertainty is a default state, says health psychologist Jos F. Brosschot of Leiden University in the Netherlands. Carry your cat into an unfamiliar empty room, he suggests. No fierce dog or hostile human is there, but there is also no obvious place to hide. Without a safe spot, the animal might be apt to claw at your chest in terror. “In the wild,” Brosschot and his colleagues wrote in a 2018 paper, “organisms have survived not by waiting for more evidence of threat but instead by erring on the side of caution.... Those who fled at the first sign of unsafety continued to live and pass their genes.”

From birth, humans have to carefully learn the cues that signal safety. For a toddler, safety is wherever their caregiver is. Over time, if we grow up in a secure environment with supportive parents, we learn to feel safe when there is no obvious danger. We become better able to tolerate uncertainty. But for those of us who grew up abused, neglected or otherwise deprived of feeling safe, uncertainty is threatening.

Uncertainty in the Lab

At the University of Reading in England, psychologist Jayne Morriss has subjected volunteers in her laboratory to unpleasant experiences that they may or may not be able to predict, from a mild electric shock to a terrifying scream. Before doing so, she already assessed them with the usual psychological tests, including the IUS. She also ascertained their thresholds for receiving a mild electric shock. Then, as they sat in front of a computer that told them whether, when or if they would receive a shock (or hear a scream), she measured their physiological responses with a magnetic resonance imaging scanner, skin conductance sensors or registers of startle response, depending on the study. Invariably, people high in IU show greater physiological distress.

One of her studies, published last year and entitled, in part, “I Told You It Was Safe,” produced intriguing results. The subjects were told that they would receive a shock at a certain time, at an unknown time, or not at all—or, more emphatically, that they definitely would not get shocked. The surprising result is that those with high IU scores showed the greatest physiological distress during the certain-to-be-safe period.

This seems counterintuitive, yet it is easy to explain. Those of us who grew up with unpredictable danger or inconsistent safety are ever vigilant for harm. “People consistently high in IU have trouble recognizing when they are safe,” Freeston says. “Just telling them it’s safe isn’t enough.”

In fact, Morriss has shown in other studies that subjects with high IU need a greater number of exposures to a now safe scenario that was previously unsafe before they have no distress response. In other words, they have more difficulty updating their perception of safety.

Tailoring Therapy

As intolerance of uncertainty has begun to be studied as a separate trait from a tendency to worry, psychologists have identified typical behaviors—often unconstructive ones—that people use to tamp down their distress at not knowing. They overprepare, perhaps memorizing answers to all the possible questions anticipated for an upcoming presentation. Some collect every bit of information they can find online and offline. They constantly seek reassurance from others and look for media sources they can trust. Or they avoid situations with unknown outcomes. If they do not know how they will do on a test, they may avoid looking at their textbooks or procrastinate. They may impulsively make a choice, even a bad one, in order to resolve their uncertainty about something. They may also decide that they know an answer and close their minds to new information.

Bredemeier adapts treatments for these patients at his clinic. To help a client feel more comfortable with uncertainty, he first has them list situations that feel mildly to intensely uncomfortable. Let’s say someone dislikes ordering from a new restaurant without first reading reviews or avoids taking a different route to work. The worst situation of all would be delegating an important task at work. The person just cannot do it.

In response, the therapist asks a client to do each task, starting with the easiest one first. A feeling of uncertainty grows, but the person stays aware of thoughts and feelings and reflects on the outcome. Maybe the client wishes they had ordered the usual takeout. Maybe they have found a favorite new restaurant. The outcome is less important than becoming more comfortable with some unpredictability. After a series of these experiments, the client is likely to score lower on IU and eventually reduce inflexible behaviors.

COVID: Uncertainty in Real Time

When the pandemic hit, none of us knew from day to day what would happen. No one knew how infections—or the threat of them—would affect work, school or travel. Nobody liked the unpredictability. Dozens of studies worldwide showed that people high in IU were at greatest risk of emotional problems.

A study published in January 2022 is especially noteworthy. Two years before COVID emerged, a team at the University of Illinois at Chicago used two methods to measure volunteers’ uncertainty intolerance during predictable and unpredictable shocks. The researchers administered the IUS self-report questionnaire before the experiment. And during it, they monitored subjects’ neural response with functional magnetic resonance imaging.

Two years later, at the height of the pandemic, the researchers asked these same volunteers detailed questions about their emotional reactions to the crisis. Having higher self-reported IU or greater activity in a brain area called the anterior insula during imaging independently predicted an increase in anxiety, depression or emotional distress.

Therapists have begun to target their patients’ uncertainty intolerance to help them through the pandemic because COVID’s unpredictability exacerbates classic IU behaviors in some people. Some read everything they can find on the Internet, wash their hands incessantly and rarely leave home. Others refuse to alter their routines even if they are putting themselves or others at risk. There are endless permutations of dealing with this continuing state of just not knowing.

As Bredemeier says, “All of us like to feel certain. It’s just a question of how much distress it causes us. Intolerance of uncertainty is a matter of degree.”