People are living in tents underneath the I-40 overpass on North Broadway in Knoxville.

10News talked to city leaders about what it's doing to address homelessness on Tuesday.

MORE: City working to address homelessness on North Broadway

Viewers posted questions about the issue on Facebook, asking specifically about mental health and its role in Knoxville's homeless population.

10News spoke with Dr. Roger Nooe, a professor emeritus at the University of Tennessee's College of Social Work. Nooe has helped author the Knoxville-Knox County Homeless Coalition's biennial studies about the homeless population since the mid-1980s. The reports detail the status of affordable and supportive housing, substance abuse and access to resources.

Nooe said over the years, the studies have shown the number of homeless people who report being treated for mental illness has increased.

"In the most recent studies, it's suggested that 60 percent of the homeless folk have been treated for mental illness," Nooe said. "And so couple that with the untreated population of mental illness, it's a very, very high, very alarming percentage."

REPORT: Homelessness in Knoxville and Knox County, Tennessee 2015-2016

Nooe said projections suggest there are about 8,000 to 9,000 homeless people in Knoxville, and about 300 to 400 of them may live near North Broadway.

"It's not a static population," Nooe said. "The most visible, as we've talked about, are the chronic homeless ... but it's also the smallest number. You've got the people who are episodically homeless."

Nooe said research shows it takes on average three tries for a person to get out of homelessness, and that can take a mental toll.

"There's another thing that I think happens is the longer you're homeless, the more there is a giving up," he said.

Nooe said people will come to cities looking for jobs and end up without a home, but he said these people most often come from surrounding counties, generally not from far away.

"That whole idea of people shipping from this city to that city ... are exaggerated and for the most part, myths," Nooe said.

Nooe thinks Knoxville city leaders have been doing a good job of working to help the homeless. He thinks more mental health outreach, more supportive housing and more coordinated efforts by organizations could help even more.

"Persons who are living on the streets often have difficulty accessing services or following through on services, so it's almost a vicious cycle," Nooe said.

He said his research has shown that the homeless population has become a lot more diverse over the years. He also said the reports have shown there are far fewer homeless veterans, which Nooe believes is due to more outreach efforts by the military.