Alcohol is strongly associated with suicidality, but again, it's difficult to prove causality (Try randomizing people to "alcohol binging group" or "suicidal ideation group"). The association is more robust than that for cannabis.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2872355/
None that I know of, but I am not as updated on research of alcohol use disorders as I am with cannabis.
One interesting frontier is using machine learning methods for causal inference (the reason I have some vague knowledge of this is that my brother is working on this...). These may hopefully allow for some interesting analyses of existing data.
Here is a link for his seminar on causal inference for observational studies: http://www.cs.nyu.edu/~shalit/slides.pdf
My personal experience has been that there's more of a correlation with alcohol, and that there's somewhat of a negative feedback loop. Considerably less so with marijuana.