Your study includes heroin which is
There are studies that show it either way. If you add heroin, which has become a problem all over, then you see a rise. If you compare just pain killers and the likelyhood of one abusing them compared to past statistics, you see a decline.
Colorado is an extreme example as it seems to be the haven for those who just wish to escape. So I wouldn't be surprised to see the numbers of heroin or opiate abusers rising at the same rate as the increase in population. But if you take other states that are not seeing the influx that colorado is, you see a decline.
Either way. It has shown benefits and certainly deserves to at least be dropped from a schedule 1 status so it can be studied further.
http://www.attn.com/stories/7829/study-opioid-overdose-down-in-medical-marijuana-states