BRUNSWICK, Maine — Service providers and advocates for those with mental illness say the sudden closure of Merrymeeting Behavioral Health Associates tears a hole in a safety net promised by the government when state-run psychiatric institutions closed decades ago.

Merrymeeting Behavioral Health Associates in Brunswick on Monday notified state and local officials that it would close on April 22 because of anticipated cuts in the state’s reimbursement rates to providers of government-funded, community-based mental health services.

That means 400 people with disabilities or who otherwise need care will lose services abruptly, making them more vulnerable and potentially damaging their health, advocates said Wednesday.

The changes, to take effect on April 8 unless the Legislature intervenes, would affect adults and children with mental illnesses and other disabilities who receive government-funded Medicaid services in what is known as Section 17 of the MaineCare Benefits Manual.

Under the changes, mentally ill patients with MaineCare could only receive Section 17 services if they are diagnosed with schizophrenia or schizoaffective disorder. The Maine Department of Health and Human Services reportedly notified more than 24,000 Mainers recently that they could lose community support services.

Maine DHHS spokeswoman Samantha Edwards said that the changes are intended to reserve Section 17 for people with “serious, persistent mental illness,” and that over the years, people who should not qualify — those with “mild and moderate” mental illnesses — have been given the services.

But advocates and others say the case management and daily living support services provided by Merrymeeting Behavioral Health Associates are crucial to keep many clients functioning without more expensive emergency or residential care.

“If they fall into crisis, they will draw more heavily on crisis services,” said Elizabeth Daly, director of integration and behavioral health homes for Sweetser. “For some — not all — conditions could conceivably deteriorate [to] where they weren’t able to live independently and might need hospitalization.”

Daly said particularly problematic is the haste with which the changes were implemented. Daly said Sweetser still hasn’t been told how to file authorization requests to meet the new requirements.

“I wish the changes to regulations didn’t happen simultaneously with the changes to rates because that just compounds the challenges, but I’m hopeful the vast majority of consumers will continue to receive some level of community-based services,” she said. “We will see whether that provides enough support, or whether we do see an uptick in high levels of services such as crisis and hospitalization.”

Rep. Ralph Tucker, D-Brunswick, said Wednesday that the cuts worsen a broken promise the state made when it de-institutionalized people with mental illness decades ago.

“In the ‘70s, [national and state] policy was emptying out state institutions,” Tucker said. “We shut down Pineland, we shut down AMHI, and the social quid pro quo was that state government would fund community services to keep people in their homes or with relatives, have their medications regulated and have counseling in the community. What’s happened now is the current governor is ripping up that bargain. What happens when people can’t get their medications on time, can’t get counseling? It ends up in job loss, lack of a paycheck, lack of an apartment, homelessness and more people showing up for lunch at the soup kitchens.”

Sagadahoc County Sheriff Joel Merry worries that “folks on the fringe” in communities near Brunswick will be unable to find replacements for the services they lose at Merrymeeting. Among other consequences, he said law enforcement will likely see an even larger increase in calls involving people with varying degrees of mental illness.

“Is there going to be anything there to pick that up?” Merry asked. “In many cases, I don’t believe there is. I just worry that the result of that may be more disturbance calls, more people not knowing how to deal with situations and making poor choices that can affect other people.”

Jenna Mehnert, executive director of NAMI Maine, said Wednesday that the elimination of reimbursement for any mental illnesses except schizophrenia and schizoaffective disorder makes no sense, because other illnesses such as bipolar disorder can cause similar or more serious symptoms.

Mehnert said the cuts affect “every single Mainer,” not just those on MaineCare, because providers rely on a volume of patients and MaineCare provides the bulk of that volume.

“The services aren’t going to exist, even if you have awesome insurance,” she said. “We already don’t pay psychiatrists enough, and now we’re going to drive more psychiatrists out of the state. And I know families who told me that if they can’t get care for their kid, they’re moving out of state.”

In a letter Monday to the Health and Human Services Committee, Lindsey Tweed, president of the Maine Council of Child and Adolescent Psychiatry, called the proposed rule and rate changes “devastating” for the more than 20,000 children who receive behavioral health services through MaineCare.

Tweed wrote that the changes “would “likely destroy” programs such as the one that has shown success in reducing incarceration of youth with aggression.

Among the most significant rate cuts are those to the already-insufficient supply of social workers who provide home and community-based treatment (13.6 percent), and to nurse practitioners who manage medications (47.8 percent), according to Tweed.

“A large cut in the [home and community-based treatment] rate will increase youth suffering and disability and will increase reliance on institutional care (hospitals, residential treatment programs, and incarceration),” Tweed wrote. “We already have a serious problem with youth being stuck in emergency departments for days and weeks at a time waiting for placement in hospitals; cutting intensive in-home treatment will exacerbate that problem.”

Daly at Sweetser and Mid Coast Hospital spokesman Steve Trockman both said Wednesday that they expect to see an increase in patients after Merrymeeting closes.

“To have an agency that busy in the community having to close precipitously, I would imagine that will have a significant impact on us,” Daly said.

At a hearing on Friday, the Legislature’s Health and Human Services Committee will hear testimony about the department’s proposal to cut reimbursement for such services.

Mehnert said NAMI will speak against the cuts, and Tucker said the hearing is the beginning of a last-ditch effort to reverse a collapse of the safety net.

“We were able to embarrass DHHS into withdrawing their reduction in services for the intellectually disabled due to the uproar in that community” Tucker said. “We want to get as many people to [the hearing on Friday] as possible, and hopefully get the administration to back down.”

Maine Department of Labor spokeswoman Julie Rabinowitz said the department’s Rapid Response team will meet next month with the 188 employees expected to lose their jobs.