The Sunshine Protection Act, passed by the House this month, promises an easy fix to an unpopular ritual: The bill would halt the twice-yearly changing of the clocks and make daylight saving time permanent.

A competing House measure, introduced in early July, would lock the clock on standard time. Now lawmakers confront three imperfect options: permanent daylight saving time, permanent standard time, or the seasonal clock-switching we have now.

Permanent daylight saving time may well be the riskiest of those choices, many scientists believe, with unintended consequences for health and the economy. Ultimately, the question is where to place an hour of daylight, a particularly scarce resource in winter.

The name of the House bill “gives the illusion that you’re increasing the amount of light,” said Jamie Zeitzer, co-director of the Center for Sleep and Circadian Sciences at Stanford University.

“But you’re not. You’re just changing when the light occurs.”

In Seattle, for example, permanent daylight saving time would push sunrise past 8:30 a.m. for roughly 10 weeks each winter. Permanent standard time would bring sunrise before 4:30 a.m. for about two months each summer.

Many sleep and circadian scientists think the disputed hour belongs in the morning. A network of clocks throughout the body coordinates everything from immune defenses to metabolism. The most potent time-setting signal for that system: sunlight.

Bright mornings and dark evenings help keep the internal clocks in sync, so the body can perform the right functions at the right times. Shifting an hour of daylight from the morning to the evening potentially disrupts this circadian system.

“The preponderance of the evidence is that daylight saving time is not good for our health or safety, and I think it shouldn’t happen,” said Elizabeth B. Klerman, a sleep and circadian researcher at Harvard Medical School and Massachusetts General Hospital.

Studies link chronic circadian misalignment to higher risks of cardiovascular and metabolic disease, some cancers and mental health problems. That’s one reason why the American Medical Association and other health, sleep and scientific organizations have endorsed permanent standard time.

Still, the appeal of permanent daylight saving time is obvious. More people would leave school and work before dark during the winter. Extra evening light might encourage exercise and socializing and, some studies suggest, reduce car accidents and rates of certain crimes.

“Where is that hour of daylight the most beneficial? I think it’s a pretty intuitive answer — when people are awake to use it,” said Steve Calandrillo, a law professor at the University of Washington who has studied the economics of daylight saving time.

The cost is darker mornings. “The worst choice of all three options is permanent D.S.T.,” said Dr. Phyllis C. Zee, director of the Center for Circadian and Sleep Medicine at Northwestern University Feinberg School of Medicine.

The country has tried it before. In January 1974 during the oil crisis, Congress imposed year-round daylight saving time. It was popular at first — until people began complaining about the “second dark age,” and children were struck and killed walking to school in the dark.

Officials scrapped the experiment, and most of the country went back to seasonal clock changes, a system some researchers now consider the lesser of three evils.

Mixed Research

The public has little appetite for keeping the status quo. Only 12 percent of Americans say they want to keep springing forward and falling back, according to an AP-NORC poll in October.

Beyond the annoyance, studies have found measurable short-term consequences to resetting the clocks: upticks in traffic accidents and heart attacks, dips in life satisfaction, even reductions in charitable giving and longer criminal sentences handed down by judges.

Settling on a permanent time brings its own trade-offs, although the evidence here is thinner.

Results of studies predicting road safety, for example, under year-round daylight saving time land all over the map — with positive, negative and no effects. Much of that research draws on clock transitions or short extensions of daylight saving time, making it hard to know how the effects would play out during a permanent change, Dr. Klerman said.

Still, one analysis exploited natural variations in sunrise and sunset times to estimate that permanent daylight saving time could prevent hundreds of pedestrian and motor-vehicle deaths a year, largely because evenings see more traffic than mornings do. Another study found that robberies dropped with extended evening light.

But such gains, scientists note, could be offset in other ways by darker mornings, chronic sleep loss and circadian disruption. Even under the current seasonal system, research suggests our circadian clocks never fully adjust to the spring shift.

So some researchers have tried to gauge the effects of permanent daylight saving time by comparing people living at different positions within time zones.

These studies link living on the western side, where the sun rises and sets later by the clock, to less sleep, lower wages and higher rates of some cancers and suicide. And one study found significantly higher rates of fatal traffic crashes in counties unusually far west in their time zones.

Modern life has muddied the picture. Many people spend their days in relatively dim indoor light and their evenings under much the same artificial light, blurring the natural contrast between day and night.

Scientists may still debate the risks and benefits of moving to permanent daylight saving time, but generally agree on one point: Different people in different places will experience them in different ways.

Worries About Children

Extreme early birds, for example, might do fine with extra evening light — it could even help them stay awake long enough to enjoy a night out.

But teenagers and night owls might struggle, scientists say. Circadian timing usually shifts later during puberty; adolescents tend to fall asleep later and wake up later. Darker mornings could dial their natural clocks later still, even as school bells force them out of bed early.

One risk: car accidents. “High schoolers are driving cars to school in the dark in the middle of their biological night,” said Horacio de la Iglesia, a biologist at the University of Washington who has studied circadian rhythms for decades.

Other potential hazards range from mental health to academic performance. Winter depression among teenagers and young adults in Russia rose after it adopted permanent daylight saving time in 2011, then fell again after the country switched to permanent standard time in 2014.

Because brains, not factories, drive much of today’s economy, student performance may be the strongest economic case against year-round daylight saving time and for year-round standard time, said Philipp Neumann, an economics researcher at Bielefeld University in Germany.

Taking advantage of Indiana’s historically uneven adoption of daylight saving time, one study found SAT test scores were an average 16 points lower in counties that observed seasonal daylight saving time compared with those on permanent standard time. The gap widened among lower-income students.

Dr. de la Iglesia studied students before and after Seattle high schools moved their morning bells to 8:45 a.m., about an hour later than before. Students slept about 34 minutes more a night, and grades and attendance improved.

Permanent daylight saving time, he said, would “undo all the benefits of the school start time delay.”

Certain businesses, however, clearly profit from later sunsets. Retail and entertainment interests have long supported daylight saving time and its extension. Candy companies, too, backed delaying the fall clock change until after Halloween.

Dr. Neumann coauthored a broad review weighing the short- and long-term effects of permanent daylight saving time and permanent standard time on health, road safety, crime, electricity use and the economy.

The conclusion: Permanent standard time came out ahead overall, driven largely by the expected health benefits.

Too Soon?

Under current law, states may opt out of daylight saving time and stay on standard time year-round, as Arizona and Hawaii do. Both bills before Congress would change the national default while leaving some room for state choice.

But too much local discretion risks recreating the very confusion that standard time zones were designed to fix, Dr. Zeitzer said.

Before U.S. railroads introduced standard time zones in 1883, towns set their clocks to strike noon when the sun reached its zenith overhead. As The New York Times put it that November, if clocks had rung an alarm at local noon from Maine to the Pacific, “there would have been a continuous ringing from the east to the west lasting for 3¼ hours.”

Returning to true local sun time isn’t practical in a modern, interconnected society, Dr. Zeitzer said — even though, biologically, he considers that standard the best solution.

Among the more viable options, scientific opinions diverge. Some researchers actually prefer the current system to either permanent alternative.

Acknowledging the limited and inconsistent evidence to date, a recent review of more than 150 studies found the effects of clock changes and seasonal daylight saving time were “not uniformly detrimental.” The authors concluded that continuing the biannual dance, while working to mitigate its negative effects, is “worth consideration — until more robust evidence emerges.”

David Prerau, a leading expert on daylight saving time, suggests that we keep the twice-yearly resets but ramp up public campaigns urging people to prepare as they would for jet lag, by getting more sleep and slowly shifting bedtimes, meals and even medication schedules ahead of transitions.

“Before we make any major change, I would at least try it,” Dr. Prerau said.

Till Roenneberg, a circadian researcher and professor emeritus at LMU Munich who has long studied human sleep timing, also sees biological logic in the seasonal switch and prefers it to permanent daylight saving time.

His own preference, though, is permanent standard time — paired with more flexible school and work start times.

The problem here isn’t really the clock but the rigid schedules society has built around it, he and other scientists say.

School and work schedules should be delayed or relaxed to better accommodate both early birds and night owls, who don’t all thrive on the same fixed clock, they say. Schedules could even be shifted with the seasons.

Permanent daylight saving time “is not a problem except for the fact that businesses are still telling people to get into work at 8 a.m.,” Dr. Zeitzer said. “And schools are still opening up at 7 a.m. or 8 a.m.”