Sen. John Fetterman, D-Pa., arrives for President Biden’s State of the Union address to a joint session of Congress at the Capitol on Feb. 7, in Washington. Carolyn Kaster/Associated Press

WASHINGTON — Pennsylvania Democratic Sen. John Fetterman, still recovering from a stroke, has checked himself into Walter Reed National Military Medical Center to seek treatment for clinical depression, his office said Thursday.

Fetterman, who has struggled with the aftereffects of a stroke he suffered last May, checked himself in Wednesday night, it said.

“While John has experienced depression off and on throughout his life, it only became severe in recent weeks,” his chief of staff, Adam Jentleson, said in a statement.

Fetterman was evaluated Monday by the attending physician of Congress, Dr. Brian P. Monahan, who recommended inpatient care at Walter Reed, Jentleson said.

“John agreed, and he is receiving treatment on a voluntary basis,” Jentleson said. “After examining John, the doctors at Walter Reed told us that John is getting the care he needs, and will soon be back to himself.”

Post-stroke depression is common, with one in three stroke patients suffering from it, and is treatable through anti-depressant medication and counseling, doctors say.

Fetterman, 53, is in his first weeks as a U.S. senator after winning the seat held by now-retired Republican Pat Toomey in a hard-fought contest against GOP nominee Dr. Mehmet Oz. Fetterman, who was Pennsylvania’s lieutenant governor, defeated the celebrity heart surgeon by 5 percentage points, flipping a seat that was key to Democrats holding the Senate majority.

Fetterman’s wife, Gisele, said she was proud of Fetterman “for asking for help and getting the care he needs.”

“After what he’s been through in the past year, there’s probably no one who wanted to talk about his own health less than John,” she wrote on Twitter.

Senate Majority Leader Chuck Schumer of New York said Fetterman “is getting the help he needs” and is expected to return soon, but declined to answer questions about Fetterman’s condition.

The Democratic caucus is “totally behind him,” Schumer said.

Fetterman suffered the stroke days before last May’s primary election and spent much of the summer recovering and off the campaign trail.

The stroke nearly killed him, he has said.

As a result of the stroke, Fetterman underwent surgery to implant a pacemaker with a defibrillator to manage two heart conditions, atrial fibrillation and cardiomyopathy.

He returned to campaigning in public in August, but refused to release his medical records or allow his doctors to answer reporters’ questions. His health became a central issue in the campaign, as Oz question of whether his opponent was honest about the effects of the stroke and whether Fetterman was fit to serve.

Fetterman’s campaign in October released a letter from a Pittsburgh-area physician who said he exhibited no effects on his “cognitive ability” or his ability to think and reason after the stroke, was recovering well and and “can work full duty in public office.”

He continues to suffer the aftereffects of the stroke, in particular auditory processing disorder, which can render someone unable to speak fluidly and quickly process spoken conversation into meaning. To manage it, Fetterman uses devices in conversations, meetings and congressional hearings that transcribe spoken words in real time.

Dr. Bruce Ovbiagele, associate dean and professor of neurology at the University of California-San Francisco, said studies have shown that someone who suffered from depression before having a stroke – like Fetterman – is at greater risk of having post-stroke depression.

It’s not clear why strokes tend to cause depression, Ovbiagele said, but strokes act on the brain and can affect behavior, and people who are having trouble recovering can get frustrated, causing depression.

Dr. Eric Lenze, head of the psychiatry department at Washington University in St. Louis, said it is heroic that a major political figure – Fetterman – admitted to being treated for depression instead of trying to hide it.

“It’s when people admit to it we start to see a reduction in the stigma around mental illness,” Lenze said. “I’m glad he admitted it. I found it a brave thing to do.”

Senators from both parties were supportive after Fetterman’s office announced the news, applauding him for getting help and acknowledging that he needed it.

Illinois Sen. Dick Durbin, the No. 2 Democrat in the Senate, learned about Fetterman’s hospitalization as he walked off the Senate floor after making a speech.

“I stand by John Fetterman and his family,” Durbin said. “This is a challenge, unimaginable challenge that he’s faced in life. He deserves the very best in professional care and I’m sure he’ll get it.”

He said he believed Fetterman would be “back in our ranks” and could serve a full six-year term.

The No. 2 Republican, Sen. John Thune of South Dakota, acknowledged he doesn’t know Fetterman very well yet but said senators were hoping and praying for his recovery.

“He’s been through a lot physically and mentally,” Thune said. “He’s got to take care of himself and his family. And I think everybody supports that.”

Last week, Fetterman stayed two days in George Washington University Hospital, checking himself in after becoming lightheaded. Fetterman’s office has said tests found no evidence of a new stroke or a seizure.

Associated Press reporters Lisa Mascaro and Stephen Groves in Washington contributed to this report. Levy reported from Harrisburg, Pennsylvania.