There isn't enough research being done on these drugs to know whether decriminalization is the right move or not
Psilocybin-occasioned mystical-type experience in combination with meditation and other spiritual practices produces enduring positive changes in psychological functioning and in trait measures of prosocial attitudes and behaviors
http://journals.sagepub.com/doi/full/10.1177/026988111773127...
Psilocybin for treatment-resistant depression: fMRI measured brain mechanisms