Sen. John Fetterman has checked himself into the hospital for clinical depression

WASHINGTON — Sen. John Fetterman, D-Pa., "checked himself into Walter Reed National Military Medical Center to receive treatment for clinical depression" on Wednesday night, his chief of staff, Adam Jentleson, said Thursday.

"While John has experienced depression off and on throughout his life, it only became severe in recent weeks," Jentleson said.

A close senior aide said Fetterman will likely remain in inpatient care for clinical depression for "a few weeks," adding that doctors are trying different medications, but they require time to identify the correct dosage.

Based on conversations the aide has had with the senator about the challenges he's faced post-stroke, the aide described Fetterman's struggle adjusting to his new reality and said the senator has wrestled with questions about his self-worth.

Fetterman suffered a stroke last year before he won the Pennsylvania Senate race in a highly competitive contest. His office said this month that he was hospitalized after he felt lightheaded but that tests ruled out another stroke.

“On Monday, John was evaluated by Dr. Brian P. Monahan, the Attending Physician of the United States Congress. Yesterday, Dr. Monahan recommended inpatient care at Walter Reed. John agreed, and he is receiving treatment on a voluntary basis," Jentleson said in a statement Thursday. “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.”

A senior aide talked about having seen Fetterman getting "more and more reserved with staff" this week and said the "withdrawn nature of it" raised alarms among those who know him well.

"This isn't who he was when he was early in recovery" from the May stroke, the aide said. "This is a much different beast."

The aide added that resignation “was never discussed, not even on the table in any sense.”

Depression is common after stroke, according to the American Stroke Association. It can result from chemical changes in the brain that make it difficult to feel positive emotions or a psychological response to the stress of the event.

“Post-stroke depression is very, very common,” said Dr. Lee Schwamm, a neurologist at Massachusetts General Hospital who is not involved with Fetterman’s care. “Estimates are somewhere up to a third of patients with stroke will have depression at some point after their stroke.”

Lee noted that severe depression requiring hospitalization, as in Fetterman’s case, is much less common.

Fetterman “had a life-threatening stroke and extraordinary treatment and amazing recovery, given where he started from, but has been under extraordinary stress and demands on him from the moment his stroke happened, and his recovery has occurred in the scrutiny of the public eye, and those are all recipes for behavioral health disorders,” Lee said.

The senator's wife, Gisele Barreto Fetterman, tweeted Thursday: “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. I’m so proud of him for asking for help and getting the care he needs.”

She added a request to respect the family’s privacy.

A short while later, in an email to supporters obtained by NBC News, she wrote: “Our family is in for some difficult days ahead, and we ask for your compassion on the path to recovery. For us, the kids will always come first. I’m never one to cover up my emotions, and today is no exception. I’m sad, and worried, as any wife and mother would be.”

President Joe Biden wished Fetterman well on Twitter Friday: "John, Gisele — Jill and I are thinking about your family today. Millions of people struggle with depression every day, often in private. Getting the care you need is brave and important. We’re grateful to you for leading by example."

Some of Fetterman’s fellow senators have also wished him well and praised him for seeking help.

Sen. Chris Murphy, D-Conn., said in an interview that he thought Fetterman's effort to seek treatment was courageous.

"I think what John has done is really courageous to step up and take care of himself," Murphy said. "He’s going to be an amazing United States senator, but we all have to look out for our health first and foremost to be able to do the best job for our constituents here in D.C.”

Senate Majority Leader Chuck Schumer, D-N.Y., offered his support on Twitter, saying: "Millions of Americans, like John, struggle with depression each day. I am looking forward to seeing him return to the Senate soon."

Senate Majority Whip Dick Durbin, D-Ill., tweeted that it's "important to take care of your mental health and it takes extreme strength to reach out when you need help."

And his fellow senator from Pennsylvania, Democrat Bob Casey, said he's "proud" of Fetterman "for getting the help he needs."

Sen. Tina Smith, D-Minn., who has talked on the Senate floor about her own experiences with depression, tweeted that pursuing "help when you need it is a sign of strength, not weakness."

Sen. Jack Reed, D-R.I., said it "takes a big man to admit when he needs help. @SenFettermanPA is a big, courageous man."

This article was originally published on NBCNews.com