Portugal is one of the hallmarks here where decriminalizing the drugs, and then spending the money on outreach, safe needle programs, and recovery centers have helped them not just with drug addiction problems they had, but also in lowering the knock-on effects of not having these things (like HIV and Hep C from dirty needles).

Like a lot of areas of life, a softer more compassionate touch yields far better results than putting people into prison and throwing away the key.