USA:

It would appear that in the States that have legalised the use of medical cannabis, suicide rates have dropped. This trend is most noticeable in young men in the 20-30 age group.
Whilst this is just another publication of extrapolated statistics, it is heartwarming to know there ARE institutions that are prepared to research the positive side of cannabis.

These stats speak for themselves:

Medical Marijuana Laws And Suicide.pdf (560kb)