(NewsNation) —In an evenly divided Senate, where gridlock is the norm, it’s rare for a bill to pass unanimously — but that’s just what happened earlier this week, when lawmakers passed an act to make daylight saving time permanent.

But Dr. Rebecca Robbins, an instructor at the Harvard Medical School and the sleep expert at the Benjamin Hotel in New York City, said this could be problematic for several reasons, largely having to do with people’s circadian rhythm.

The circadian rhythm refers to what happens in the brain and body in approximately 24 hours, Robbins said.

Light exposure, especially natural daylight, is the strongest input to people’s circadian rhythm.

“On daylight saving time, we’re essentially scooting our clocks forward and borrowing from the morning light and adding that morning light to the evening,” Robbins said.

Having more exposure to natural light in the evening hours, after not being able to get it in the morning, puts a lot of the cells in the body operating in a 24-hour fashion out of sync, “putting us at risk for a host of adverse health outcomes,” she said.

“That curtails the secretion of melatonin in the brain that then allows sleep to follow,” Robbins said. “So if you’re feeling that way, that’s a sure sign that you’re in a little bit of desynchrony.”

There’s evidence showing that when people change their clocks bi-annually, it’s hard to adjust to the time change, Robbins said.

“We all feel a big relief when we get to standard in the fall,” she said.

The bipartisan bill changing daylight saving, called the Sunshine Protection Act, still needs approval from the House, and the signature of President Joe Biden, to become law.

“No more switching clocks, more daylight hours to spend outside after school and after work, and more smiles — that is what we get with permanent daylight saving time,” Sen. Ed Markey of Massachusetts, who co-sponsored the legislation, said in a statement.

Republican Sen. Rick Scott of Florida called changing the clock twice a year “outdated and unnecessary.”

Making daylight saving time permanent happened once before in the U.S., when in 1973 then-President President Richard Nixon signed an emergency daylight saving time bill into law in an attempt to cut electricity demand by extending daylight hours.

It didn’t go well.

“It wasn’t desirable,” Robbins said. “People reported not being happy under those conditions but also, importantly, we saw an increase in safety risks.”

Should the U.S. make this change again, Western states, in particular, will really struggle because of their time zone, Robbins said.

“When the fall rolls around, those on the Western points are going to get sunlight at 9, 9:30, 10 o’clock in the morning, and so are our young ones who are going to be trying to hop on the bus and navigate along our streets in the darkness,” Robbins said. “That’s just one example of the safety risks that we could be facing if we were to stay on this permanent daylight saving time.”

Over the last four years, 18 states have enacted legislation or passed resolutions calling for year-round daylight saving time, according to the National Conference of State Legislatures.