Housing, healthcare, mental health, public transit, unemployment, lead abatement, education - all of these policy levers impact the prevalence of the behaviors you describe.
The kind of people who destroy public spaces and public toilets will also destroy any free housing you give them. If by "mental health" you mean involuntary commitment, then yes, that will do the job
"Cities like Helsinki and Vienna in Europe have seen dramatic reductions in homelessness due to the adaptation of Housing First policies, as have the North American cities Columbus, Ohio, Salt Lake City, Utah, and Medicine Hat, Alberta."
"A decade ago, Utah set itself an ambitious goal: end chronic homelessness. As of 2015, the state can just about declare victory: The population of chronically homeless people has dropped by 91 percent."
"Finland has adopted a Housing First policy, whereby social services assign homeless individuals homes first, and issues like mental health and substance abuse are treated second. Since its launch in 2008, the number of homeless people in Finland has decreased by roughly 30%,[1] though other reports indicate it could be up to 50%. The number of long-term homeless people has fallen by more than 35%. "Sleeping rough", the practice of sleeping outside, has been largely eradicated in Helsinki, where only one 50-bed night shelter remains."
Having a stable housing situation turns out to make a whole bunch of other related social changes more feasible.
> If by 'mental health' you mean involuntary commitment, then yes, that will do the job
I mean, I'd start with therapy, addiction services, social supports, and the like. But I do think the complete removal of long-term inpatient mental health in the 50s/60s was an overshoot. Some people need that much help.
(I also believe there's a lot more we can do to prevent people from becoming that "kind of people" in the first place.)
Housing, healthcare, mental health, public transit, unemployment, lead abatement, education - all of these policy levers impact the prevalence of the behaviors you describe.