US health officials reversed course and began reinstating nearly $2bn in cuts to mental health and substance use programs on Wednesday night, one day after they unexpectedly announced the immediate shutdown of programs.

The reversal is a blow to the agenda of Robert F Kennedy Jr, the secretary of the US Department of Health and Human Services, who has made aggressive and legally contested cuts to health agencies in the first year of the Trump administration and has proposed folding the Substance Abuse and Mental Health Services Administration (Samhsa) into a new agency he would call the Administration for a Healthy America (AHA).

There was immediate outcry about the effects of shutting down vital programs amounting to one-quarter of the budget of Samhsa.

The cuts would have affected overdose prevention and reversal, mental health and substance use support for children, mental health training and support for first responders, support for pregnant and postpartum women, and recovery support programs.

Some programs received reinstatement letters late Wednesday night, while others are still waiting for official notice that their programs could resume, sources told the Guardian.

Representative Rosa DeLauro, ranking member of the House appropriations committee, seemed to confirm the reversal in a statement late Wednesday.

“After national outrage, Secretary Kennedy has bowed to public pressure and reinstated $2 billion in SAMHSA grants that save lives,” DeLauro said. “These are cuts he should not have issued in the first place,” and they “created uncertainty and confusion for families and healthcare providers,” DeLauro said.

An administration official also confirmed to the New York Times that money was being restored, but did not say why. It was not immediately clear if all grants were re-established.

As lawmakers continue to negotiate over the federal budget, some suspected that the move was a political play. “Congress holds the power of the purse, and the Secretary must follow the law,” DeLauro added in her statement.

“Today, first responders tackling the fentanyl crisis spent the day planning layoffs instead of helping people,” Patty Murray, a Democratic Washington senator, said on X when reports first indicated the cuts were being reversed. The cuts caused “absurd, pointless chaos” from Kennedy and the Trump administration, she said.

While the reversal was a victory for organizations providing substance use and mental health services, US officials may continue making deep cuts to the health programs upon which millions of Americans rely, experts said.

“This reinstatement of funds is a good thing for the American people and we should view these actions in their whole,” Dr Sunny Patel, a former senior official at Samhsa and associate professor at the Thrive Center for Children, Families, and Communities at Georgetown. “This administration has shown its political project to systematically dismantle the behavioral health system.”

The administration has made sweeping cuts to budgets and staff at health agencies, and the confusion and instability will worsen children’s behavioral health, Patel and Matthew Biel wrote in Health Affairs on Wednesday.

Shoring up health amid repeated uncertainty and cuts “requires vigilance and sometimes outrage”, Patel said. As the reversal shows, he said: “Advocacy works.”