Chicago has for decades been dealing with a so-called "death gap," in which life expectancy in one neighborhood can be 20 years lower than in others. Mayor Brandon Johnson tells CBS News his administration is working to address that discrepancy, which he said is driven by homicides and drug overdoses.

According to 2023 numbers from the Chicago Department of Public Health, life expectancy in the neighborhood known as the Loop was 87.3 years, the highest of any Chicago neighborhood. In West Garfield Park, life expectancy was just 66.6 years, the lowest of all the city's neighborhoods.

Johnson, who has been in office since May 2023, said homicides were down 30% last year and there was also a 34% decrease in drug overdoses. 

"I'm confident that as we continue to do the work that's necessary to invest in these communities, we can improve the quality of life for all Chicagoans," Johnson told "CBS Evening News" anchor Tony Dokoupil on Wednesday. 

Asked why, if the gap has been a known problem for so long, nobody else has solved it, Johnson said, "Unfortunately, for a very long time, every level of government has been focused on neighborhoods that, quite frankly, do not need the type of investments that West Garfield Park and neighborhoods like that across the country deserve." 

"We have transformed, essentially, how we are approaching leadership in this moment, by focusing our attention on neighborhoods that need these critical investments, whether it's youth employment, whether it's education, whether it's health care — particularly mental health care — that's what my focus has been," Johnson said. 

When determining what comes first, investments or rooting out drugs and crime in order to improve the quality of life for people in neighborhoods with lower life expectancies, Johnson said it's a combination of both.

He said that, for neighborhoods that need larger investments in areas like education and housing, "We have to do that now. But of course, we have to address these decades-old challenges that have been ignored for a very long time." 

"That's why we have done a strategic partnership around policing and affordable housing, policing and youth employment, policing and mental health care services," Johnson added. "By taking that full-force-of-government approach that allows for us to address the critical issue, the immediate need, while setting us up for long-term viability."

Johnson said the city is heading in the right direction, but knows there's still more work to do, and lamented a lack of help from the federal government.

"We know the Trump administration just cut $2 billion away from mental health care services, that's problematic," he said. The Trump administration has since reversed those cuts, sources told CBS News on Thursday. 

 "We're investing in mental health, so we are at the beginning of a transformation, and I'm confident if we continue to come together, we'll see the type of life expectancy for all Chicagoans that we can be proud of," Johnson said.