[Wolfie]

"Scientists cannot rule out that pre-existing conditions could have led to both marijuana use and later psychoses, he added."

In other words, more Junk Science.

[Long Island Pete]

There just might be some truth to this story.

[Thermalseeker]

In other words, more Junk Science.

I wonder how much "Palmie" tax money was spent on this "study"?

[Zon]

In how many deaths has alcohol been determined to be the cause of death? 
In how many deaths has marijuana been determined to be the cause of death?

What percentage of people that consume alcohol die from it?
What percentage of people that consume marijuana die from it?

What's the ratio of people that act out violently under the influence of alcohol? 
What's the ratio of people that act out violently under the influence of marijuana?

Who should decide what a person puts or doesn't put into their body, the individual or the government?

[ModelBreaker]

"Scientists cannot rule out that pre-existing conditions could have led to both marijuana use and later psychoses, he added." . . . In other words, more Junk Science.

Well, that's a quite a bit too strong a statement. The authors found correlation but, as scientists, they noted (correctly) that correlation does not mean causation. To establish causation would require a controlled experiment which, for this question, would not be possible. So the authors properly note that causation could be a chain of causation different than pot -> crazy. Causation could be, for example,

Defective Brain Wiring -> Pot Use and
Defective Brain Wiring -> Crazy.

That would make Pot and Crazy correlated but not causative. That's all the authors said.

So this is NOT junk science. It is scientists doing their job by noting the limitations of their study.