http://thechart.blogs.cnn.com/2011/02/07/marijuana-use-may-speed-psychosis/
From that link:
'marijuana users experienced psychosis about three years younger than non-users.'
Two different groups of people, not a longitudinal study. Here's what researchers say about what can be concluded:
'experts say the complexity of interaction between genes and environment, and the possibility that cannabis is, in fact, a way to self-medicate when psychotic symptoms arise are not accounted for in this study.
'"It is distinctly possible, in fact likely, that folks who experience initial symptoms turn to cannabis in an effort to control them, then end up having a psychotic break of some sort earlier simply because they had their first symptoms earlier," said Mitch Earleywine, an associate professor of psychology at the State University of New York at Albany, who is also a marijuana policy expert. "This predicament makes it look as if cannabis preceded the psychotic symptoms when, in fact...folks with worse symptoms who are more likely to have an early break might simply be more likely to turn to cannabis."
'Theories about an association between marijuana use and schizophrenia include several – sometimes interrelated - scenarios: The possibility that cannabis causes schizophrenia; that cannabis may cause people vulnerable to schizophrenia to develop symptoms; that cannabis may make schizophrenia symptoms worse; or that people with schizophrenia are more likely to use cannabis, according to the study.'
'March 1, 2011 — Adolescents and young adults who smoke marijuana have an increased risk for experiencing psychotic symptoms, according to a new study.
'The new findings appear online in the journal BMJ.
'Researchers assessed marijuana use during a 10-year study of 1,923 participants aged 14 to 24 in Germany.
'Those participants who had no psychotic symptoms and had never tried marijuana when the study began and then started using marijuana had nearly double the risk of experiencing psychotic symptoms in the future.
Notice that they don't say what the risk was as a percentage with or without marijuana use - just as researchers report a cancer risk from chemical X without mentioning that it increases the risk from (say) one in a billion to two in a billion.
'And those who used marijuana before start of the study and who continued use over the study period had an increased risk of persistent psychotic symptoms, the study shows.
'“Our study confirmed cannabis as an environmental risk factor, impacting on the risk of psychosis by increasing the risk of incident psychotic experiences and if use continues over time, increasing the risk of persistent psychotic experiences,”'
http://www.webmd.com/mental-health/news/20110301/marijuana-use-linked-to-risk-of-psychotic-symptoms
This confirms that marijuana use precedes psychotic experiences - but since marijuana use was subject-self-selected rather than randomly assigned by the researchers, it doesn't exclude the possibility that the same people who are predisposed to use marijuana are also predisposed to later psychotic experiences.
“With higher doses and with certain unstable or susceptible individuals, marijuana can produce extreme euphoria, hilarity, and overtalkativeness, but it can also produce intense anxiety and depression as well as delusions, hallucination, and other psychotic-like experiences
You do know that ‘produce’ means to ‘cause to exist, or yeild,’ right?
That passage describes short-term effects. You didn't think marijuana produced long-term persistent euphoria, hilarity, and overtalkativeness, did you?
Then you first say “Again, no such longitudinal studies have been done - the results under discussion compared one set of people who used marijuana to a different set of people who didn’t. “
But in the next breath say “Whether a study is longitudinal has nothing to do with whether it establishes a link.”
No contradiction - a longitudinal study is capable of coming to the conclusion that no link exists.
Then we go off onto another rabbit trail talking about the “the strength of the relationship is the size of the correlation coefficient, which has nothing to do with the magnitude of the effect.”
Now we’re apaprently discussing ‘magnitude of effect’ or rather how strogn an effect is? Then we go to ‘Magnitude of increase in frequency’?
They're all the same thing. The contradiction is only in your mind.
Then you state "If all test subjects who take chemical Z grow in height by exactly 0.001 inches, that’s a maximum strength of relationship but a low magnitude of increase."
I’ll ask it again- where does the study indicate that magnitude of increase was so low?
The point is your incorrect belief that large strength of relationship implies large magnitude of increase.
a cotnrolled study where all the variables are known and accoutned for
Where did the researchers claim that?
[[’”It is distinctly possible, in fact likely, that folks who experience initial symptoms turn to cannabis in an effort to control them,]]
so lemme get thsi straight- You don’t think a person can come to a reasonmable assumption based on a study when arguing a conenction, but you do think assumptions are just fine when assuming htere might be ‘other reasons or factors’ despoite hte evidence showing that thsoe who don’t take drugs experience less events while thsoe that do expeirence more? You also later throwi n an assumption that peopel are predisposed to use pot- throwingi n an unproven wildcard into the mix akin to what wiki does-
The discussion was not abotu whether peopel using drugs experienced events earleir in life, the dicussio nwas abotu whether using drugs whiel beign a psychotic can contribute to increased psychotic events- let’s just stick to that issue-
[[predisposed to use marijuana are also predisposed to later psychotic experiences. -]]
‘predisposed to use pot’? Really? Pot use is a condition? Not a choice?
[[You do know that ‘produce’ means to ‘cause to exist, or yeild,’ right?
-—That passage describes short-term effects.]]
Yeah? So?
[[Now we’re apaprently discussing ‘magnitude of effect’ or rather how strogn an effect is? Then we go to ‘Magnitude of increase in frequency’?
They’re all the same thing. The contradiction is only in your mind.]]
No sir- they are different issues altoghehter- One is how strogn an effect is, the other is how how often an event happens- and has nothign to do with how strogn the effect is while the event is taking place-