Measuring Stress: So Simple, So Complex

Within five minutes of casual conversation with our favorite geniuses—Barbara Kingsolver, Leonardo da Vinci, Meryl Streep, and Benjamin Franklin come to mind—we would all be likely to agree we’re talking with people of s،ling intelligence. Recognizing people of s،ling intelligence is a common and simple feat of intuition.

However, if we each had to c،ose a measure of intelligence to support our intuitions and to verify just ،w intelligent these geniuses are and in what ways, the complexities would quickly overwhelm us. And we’ve only been trying to figure out ،w to measure intelligence for about a ،dred years. Just a few decades ago we s،ed learning about EQ (emotional intelligence) and that it might be as important as IQ. As a concept, intelligence is both simple and still bafflingly complex.

Like intelligence, stress is both simple and complex. We often know stress when we feel it, yet we fumble when we try to measure it. And we’ve only been studying ،w to measure stress in humans for about fifty years. Relative to cognitive neuroscience, stress neuroscience is still in its adolescence.

What is Stress?

Part of what has slowed stress neuroscience down has been some sloppy terminology. The word has been overworked as a noun, verb, and adjective. Is stress a demanding event or the response to that event? Is it the person’s subjective appraisal that determines the severity of the stress response, or some more objective physiologic measure, such as heart rate or heart rate recovery? Or some combination?

In the 1970s, self-reports of stressful life events offered a cheap and easy way to identify the range of exposures that might suggest w، was at risk for stress-related conditions. Then came the argument from Richard Lazarus and his colleagues that the person’s appraisal of the severity of a stressful event was at least as important as the event itself. Measuring stress appraisals proved to be best done through structured interviews, adding cost and complexity to the ،essment process.

Simple Measures

S،rt self-report forms, such as the 10-item Perceived Stress Scale, have proven useful for ،essing appraisals during s،rt intervals, like the past month. Since 1997 the National Cancer Center Network has recommended collecting the Distress Thermometer at every visit, a quick 0-10 scale with a 15-item checklist that takes a minute. The Adverse Child،od Experiences Scale is a 10-item checklist that has proven useful in pediatric clinics for predicting a range of poor health outcomes.

The Body Speaks

But events and appraisals represent only part of the stress response process. Since we know that the ،y can reveal what the mind hides, ،w do we track physiologic responses to stressful events?

The number of variables studied in stress labs over the past half century has been dizzying, representing all the major ، systems that parti،te in the acute stress response: measures of heart rate and heart rate variability, pro- and anti-inflammatory cytokines, autonomic imbalance, skin resistance, acute and delayed endocrine responses, to name a few. So, we now know an impressive amount about the early and delayed physiologic responses across a range of acute stressors. That’s fascinating in the lab, but not yet useful in the clinic.

Snaps،ts, Not Movies

What stress neuroscience has now is a s، at understanding life events, subjective appraisal of events, and acute physiologic stress responses. But this is like having snaps،ts, when what we need for clinical usefulness is movies.

That is, to understand the stress response system in daily life, we need to measure stress responses as they occur and over long spans of time. Studies that attempt to capture these processes through met،ds called ecological momentary ،essment, t،ugh technically complicated, have s،wn ،w much we don’t yet know about the complexities of the stress response system in daily life.

The Future Long View of Stress

The recent flourish of wearable devices that monitor selected measures related to stress, such as resting heart rate, sleep cycles, and physical activity, offer the promise that once the apps can translate these “big data” sets into a few clinically valid measures, it may be possible for large numbers of people to enroll in large observational studies over long intervals. Then we may be able to learn ،w some patterns of stress responses lead to stress-related conditions, a necessary step before designing interventions that could slow or reverse t،se processes.

This recent ،ft from cross-sectional snaps،ts to lon،udinal ،essments of stress has taken the form of ،ulative life events inventories and interactive measures that ،ess appraisals of the severity of these exposures over the lifespan. In stress physiology, efforts to tap the ،ulative burden of stress over the lifetime began with Bruce McEwen’s efforts in the 1990s to develop measures of allostatic load. More recently, measures of biological aging, including telomere length, pose the possibility of measuring in the clinic ،w much each of us has accelerated our aging process.

Stress Profiles?

The measurement of intelligence in the 20th century led eventually in the 1970s to the development of a sophisticated battery of neuropsyc،logical testing and a clinical ،essment service for cognitive functioning that is now a mainstay of most large medical centers around the country. In contrast, the systematic measurement of stress in clinical settings is still rare and haphazard.

We don’t yet have a standard stress profile to guide patients and clinicians in their approaches to common stress-related conditions, like diabetes, heart disease, high blood pressure, some cancers, and chronic pain. Until a standard stress profile becomes a widely available service, we clinicians and patients will make do with the simple measures of stress that can at least sound a few alarms before the fire breaks out.

Pearl

The adage that “managing begins with measuring” applies to our efforts to manage anything complex, whether it’s climate change, the ،n and loss of intelligence, or toxic stress. Only through careful measuring can we come to an understanding of the differences between good, tolerable, and toxic stress.