Environmental factors cause decreased intelligence quotient (IQ) in adolescents, not the use of marijuana. "The types of environment where you are, are important factors that affect your IQ," said Ole Røgeberg, a labor economist at the Ragnar Frisch Centre for Economic Research in Oslo, Norway.
Røgeberg's statement is part of the research results were published on Monday (January 14, 2013) in the journal Proceedings of the National Academy of Sciences. These findings refute the result research of Duke University scientists team (published August 2012) that mentions marijuana use factor as the main cause of IQ decline.
The studies conducted by Røgeberg shows factors related to economic class and living in the house. He uses computer simulations to show the link between these factors and the IQ decreased. According Røgeberg, a good education and challenging work can improve intelligence. However, he said further if someone pushed out of the neighborhood, would tend to be the type that marijuana use during adolescence.
In the previous studies conducted by Madeline Meier, Terrie Moffitt and Avshalom Caspi from Duke University, who used data of 1,037 citizens of Dunedin, New Zealand. Thorough study over three decades of tracking respondents aged 7 years and over. They see the results of an IQ test, blood sample, and interviewed their parents and teachers. The team found that the marijuana use as many as eight points lower IQ, for users who start in adolescence.
Røgeberg created a mathematical model in order to see the impact of marijuana on IQ with social-economic factors. He explained doesn't mean marijuana is not harmless. According to him, the Duke University team should be analyzed more thoroughly in order to prove only the marijuana use (and not other factors) as the cause of IQ decline.
Røgeberg said, they should examine whether the use of marijuana change the trajectory of individuals IQ from the age of 7 years and beyond. Researchers also need to look at the cumulative impact of various factors, such as living in a house or education level. "Perhaps the totality of factors can explain most of the effects they found," he said.
Duke University team responded to objections from Røgeberg. They analyzed and found that IQ remains stable. They also include the children from middle-class families and eliminate the socio-economic status effects. But Røgeberg says those steps can't rule out other factors as the cause for lower IQ. "While interesting, the new analysis is not at all sufficient to address these concerns – but I look forward to seeing a fuller analysis in time," Røgeberg said. *** [EKA | FROM VARIOUS SOURCES | LIVESCIENCE | KORAN TEMPO 4116]
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