Prohibition is clearly stupid and has caused very great harm. Other people have mentioned the death and destruction in Mexico as one example. I am strongly pro legalisation.
But the links between cannabis and mental ill health remain unclear. We don't know how many people have mental illness caused by cannabis; we don't know how many people with an underlying illness have that illness triggered by cannabis; we don't know how many people with an existing illness are self-medicating with cannabis. (Legalisation will help. Researchers now have the ability to do better science.)
Mental health treatment in America is sub-optimal. I am concerned that legalisation and the lack of good health care is a bad combination. But this is just a gentle concern - I am still strongly pro legalisation.
Nicotine & Alcohol both cause mental and physiological illnesses — a lot of them actually. Marijuana can be linked to certain types of psychosis, depending on which study you read.
It's a risk. Personally, I favour the Norwegian model: tax it highly, put the tax gains into the public health sector. Everybody wins.
I have nothing to offer but what I've heard and anecdotal experience. People often get "mentally ill" from marijuana because it can produce mild feelings of paranoia. Add to that a country which will arrest you for it. And forcing people to buy it illegally from armed criminals, and you'll surely get people who crack under the pressure. I'm not saying that it's total bunk that marijuana causes mental problems, but I think a lot of it is attributable to its illegality.
The purpose of prohibition was to destroy local, independant breweries and distillers, so that large conglomerates would be able to dominate the very lucrative alcohol industry once it was re-legalized.
Look at who the owners of breweries and distilleries were pre-Prohibition, and after. Before - small businesses, essentially micro-brewers, spread out across the country. After - Anheuser-Busch and a few others. QED.
Similarly, the purpose of World War 2 was to destroy other industrialized nations so that the United States could dominate the very lucrative world economy once peace was reattained.
Just look at who the world powers were pre-World War, and after.
America's strength is why the USD became the reserve currency of the world. Note that the Bretton Woods conference was held in 1944, before the war ended: http://en.wikipedia.org/wiki/Bretton_Woods_system
Because large breweries back then had trouble dominating smaller distributers? They decided to shutdown for 13 years, to destroy independent breweries?
A conspiracy this large would be quite easy to prove. I'm sure you are willing to share all of your evidence without relying on your ipso facto conclusion.
There are questions of whether a link exists between cannabis use and adult-onset schizophrenia (ie, a "psychotic break" in the early 20s).
The problem is that these variables are highly confounded - not only is it reasonable, but it is almost expected that a person who is experiencing early signs of schizophrenia (even if they don't realize it) might have their life impacted enough that they turn to alcohol or marijuana (or other drugs) to address those secondary problems, even though schizophrenia would be the underlying root "cause".
The question is not whether that second effect (schizophrenia causing drug use) exists, but the magnitude of that relationship. Which is difficult to measure on a theoretical level, and perhaps impossible to measure on an ethical level.
But the links between cannabis and mental ill health remain unclear. We don't know how many people have mental illness caused by cannabis; we don't know how many people with an underlying illness have that illness triggered by cannabis; we don't know how many people with an existing illness are self-medicating with cannabis. (Legalisation will help. Researchers now have the ability to do better science.)
Mental health treatment in America is sub-optimal. I am concerned that legalisation and the lack of good health care is a bad combination. But this is just a gentle concern - I am still strongly pro legalisation.