Legalize drugs. Without drug money and the extra-normal profits enabled by drug dealing, a large chunk of the problem would go away, with the added benefit tax revenue benefit.

See further the New Yorker's article on Portugal's drug decriminalization experiment: http://www.newyorker.com/reporting/2011/10/17/111017fa_fact_... . It's behind a paywall but worth reading if you can get to it.