I don't know what you are looking at but this researcher shows a huge increase in bipolar disorder.
"According to the 1969 book, Manic Depressive Illness by George Winokur of Washington University, Bipolar Disorder used to be fairly rare. In 1955, only one person in every 13,000 was hospitalized for it. Today, by contrast, according to the National Institute of Mental Health, Bipolar Disorder affects an astounding one in every forty adults in our country!!! "
I don't know what you are looking at but this researcher shows a huge increase in bipolar disorder.
Bipolar disorder is not the same as schizophrenia, whose rates are indeed flat: "But here's the conundrum: while marijuana went from being a secret shared by a small community of hepcats and beatniks in the 1940s and '50s to a rite of passage for some 70% of youth by the turn of the century, rates of schizophrenia in the U.S. have remained flat, or possibly declined. For as long as it has been tracked, schizophrenia has been found to affect about 1% of the population." (http://www.time.com/time/health/article/0,8599,2005559,00.html)
“I don’t know what you are looking at but this researcher shows a huge increase in bipolar disorder.”
And this one says: “The number of American children and adolescents treated for bipolar disorder increased 40-fold from 1994 to 2003”. If you truly believe that is objective, I got a bridge to sell you. Also, cannabis use decreased during those years.
http://www.nytimes.com/2007/09/03/world/americas/03iht-health.4.7366376.html
Psychiatric evidence is very subjective. I don’t like to use it but prohibitionists like to flaunt it now because it has been established there is absolutely no evidence of proven physical damage. There has never been a SINGLE autopsy that proves any damage from cannabis. All while such damage occurs from alcohol every single day.