Duke Study On Marijuana And IQ Challenged

Research supported by Duke University scientists linking marijuana use to a drop in I-Q is being questioned. 

Last August researchers at Duke published a study that followed habitual users of marijuana in New Zealand before they turned 18. Subjects of that study showed an average drop of eight I-Q points when their aptitude was measured. 

The News and Observer reports a Norwegian researcher is now disputing the study. That scientist says his research shows factors such as education, income and job status among the study's participants may also  have contributed to a downward trend in their I-Q.  Duke researchers learned of the Norwegian study a week ago.  They conducted more analysis of the data and stand by their findings.  Scientists independent of both analyses have looked at the findings and concluded that neither study definitively determines a cause for lower I-Q.