*The following is excerpted from an online article from HealthDay.
Occasional marijuana use does not appear to affect teens' intelligence or school performance, but heavy marijuana use is associated with slightly lower exam scores, according to a new study.
Among more than 2,200 U.K. children who took IQ tests at age 8 and at age 15, marijuana use in the teen years appeared to be associated with lower IQ scores, the researchers said.
However, the researchers found a strong link between marijuana use and other risky behaviors such as alcohol, cigarette and drug use. When these other behaviors were taken into account, there was no connection between marijuana use and lower IQ at age 15, they said.
The study did find that heavy marijuana users (at least 50 times by age 15) scored an average of 3 percent lower on compulsory school exams taken at age 16.
The findings were presented at a meeting of the European College of Neuropsychopharmacology in Berlin, Germany.