They're beady-eyed, bald-tailed and thriving in the city's trash-strewn alleys and vacant houses.

Many in Baltimore would agree that seeing rats regularly is annoying. But for some, the rodents' constant presence can also be depressing.

Residents who see rats the most in their neighborhoods and their homes are significantly more likely to suffer from sadness, anxiety and other depressive symptoms, according to researchers at the Johns Hopkins Bloomberg School of Public Health.

“This study provides very strong evidence that rats are an underappreciated stressor that affects how people feel about their lives in low-income neighborhoods,” said Danielle German, an assistant professor in the Department of Health, Behavior and Society who led the study.

German said researchers trying to understand the main stressors in low-income neighborhoods were surprised to learn that “rats and trash” were repeatedly cited as top public health concerns of people who were living in areas that were also affected by crime, street-level drug-dealing, and vacant and deteriorating housing.

About half the 448 residents interviewed in 2010 and 2011 reported seeing rats on their block at least weekly. More than a third said they saw them daily. About 13 percent said they saw rats inside their homes.

Researchers found that those who considered the rats a big problem were 72 percent more likely to experience depressive symptoms than those who lived in similar neighborhoods where rats weren't a big problem.

German said the findings could change the way public health and other officials frame the conversation about rats, usually considered a nuisance and a vector for disease more than a depressive force.

“That misses what it feels like to be a resident of a neighborhood where you see rats every day,” she said.

Since the study was conducted, German said, the city has taken some steps that might help. Chief among them is a $10 million plan to distribute sturdy trash cans with lids to every resident, which began in recent weeks.

In Belair-Edison, where cans were passed out more than a year ago under a pilot program, the impact was swift, Sadie Gooch said.

The 70-year-old resident said she used to see rats every day. Now she can't remember the last time one scurried through her yard.

Gooch said neighbors embraced the cans, which have cleared many blocks of trash. The lids fit tightly, she said, so the rats don't go looking for food or shelter.

“I didn't like going out my back door at night because of the rats, and now I'm not scared to sit out there,” she said. “I don't know about rats making people sad and anxious, but they scared me.”

Now, she said, bulk trash and dog feces are neighborhood problems, but the rats aren't as interested in that refuse.

It was such feedback — and a 25 percent drop in calls about rats — from Belair-Edison and Greater Mondawmin, another neighborhood with a pilot program, that led Mayor Stephanie Rawlings-Blake to roll out the trash can program citywide, spokesman Howard Libit said.

The city has stepped up other rat control efforts, such as treating rat habitats proactively, rather than waiting for calls.

The city's rat budget for fiscal 2016 was just under $1.1 million and included 16 workers, up from nearly $619,000 and eight workers the year before, according to the Department of Public Works.

Libit said the measures were born largely of concern about public health — and the fact that most people absolutely hate rats.

“Reducing rats is something we want to do for the people who live in neighborhoods where they are prevalent,” he said. “They are disgusting.”

meredith.cohn@baltsun.com