Rep. Tom Kean Jr. said he was diagnosed with depression this year and doctors recommended inpatient treatment that kept him from his job in Washington.

The 57-year-old New Jersey Republican announced the diagnosis on Tuesday upon his return to Congress after a nearly 4-month absence.

“When people hear the word depression, many people think you simply feel sad,” he said in a floor speech. “But depression is so much more than that. It is physical. It is emotional.”

Mr. Kean has not voted in Congress since March 5 and had not been seen in public until earlier this month after he announced he would return to work in Washington soon.

The second-term congressman had attributed his absence to a health condition but did not disclose details before his return.

Mr. Kean said he checked himself into the hospital several months ago “due to health concerns” and underwent testing. When the doctors diagnosed him with depression, they recommended that he remain in the hospital for treatment.

“They explained to me that this would be the fastest way to recover, and to be honest, I was hesitant,” he said. “I didn’t think that I had time for it. I had responsibility to my family. I had responsibilities to my constituents. I had responsibility to this institution. And like many people, I believed that I could simply push through.”

The congressman decided to listen to his doctor’s advice but did not anticipate a long-term stay. His initial statement announcing his absence due to a medical issue predicted he would return within weeks, which he said was the best estimate the doctors could provide at the time.

“But as the over 14 million fellow Americans being treated for this illness have come to discover, there is no timeline for healing,” he said. “There is no timeline for recovery, only the work of getting better one day at a time.”

Mr. Kean said his doctors have cleared him to return to work and that he’s grateful for his constituents’ patience and understanding during his absence.

“I am grateful that I accepted this help, because today I stand before you healthier, stronger and excited to return to the work that I love,” he said.

House Speaker Mike Johnson, Louisiana Republican, told reporters earlier this month that Mr. Kean was “in good spirits” but that he was honoring the congressman’s wishes not to disclose his medical issue.

Shortly before the congressman’s speech, Mr. Johnson told reporters he believes Mr. Kean will “get a lot of empathy” after disclosing his health diagnosis.

“It’s not an uncommon kind of condition and ailment that he’s been fighting, and I think people will resonate with that,” the speaker said.

Mr. Johnson called Mr. Kean “a genuinely good man” and “a person of integrity,” but suggested he could have been more transparent about his condition before his return.

“If it were me, I would have been more specific about that, and I encouraged him to be,” Mr. Johnson said. “He will today. But it will be understandable to you.”

Mr. Kean said he’s a private person by nature and that talking about himself “has never come naturally.” He said he decided to speak out about his depression diagnosis because he owes it to his constituents and he hopes it could help others struggling with their mental health.  

“If sharing my story encourages even one person to seek help, to give one family courage to have a difficult conversation, or remind one person that recovery is possible, then this moment will have been worthwhile,” he said.

Mr. Kean ran unopposed in New Jersey’s Republican primary on June 2.

He put out a statement as voters headed to the polls, saying he would be transitioning from virtual to in-person work “within a matter of weeks” and at that time would be “completely transparent as to the nature of my medical condition.”

Democrats view Mr. Kean’s seat as a prime pickup opportunity in the midterms this fall. President Trump won New Jersey’s 7th Congressional District by a single point in the 2024 presidential election.

Rebecca Bennett, a former Navy helicopter pilot, is the Democratic nominee.

A poll conducted in late May before the primary found Ms. Bennett leading Mr. Kean in a head-to-head matchup by 4 percentage points.

The Democratic Congressional Campaign Committee is attacking Mr. Kean for not being transparent with his constituents during his absence and for scheduling a campaign fundraiser on his first evening back in Washington.