For teenagers who smoke pot daily before they are 18 years old, the result may be neuropsychological decline meaning a drop in their IQ. This continues even after they quit smoking.
Teens using more and more frequently
Researchers found that early-onset regular pot smokers had IQs 8 points lower than their peers who never smoked or started smoking after 18. Unfortunately, as more teens believe that pot smoking is a harmless pastime, the age of first use is dropping and persistent use is increasing. Daily use of marijuana is higher than it’s ever been according to study leader Madeline Meier, post doctoral researcher at Duke University in Durham, NC.
Research followed people from birth
Researchers set out to discover if there was any link between cannabis use and drop in IQ. They also wanted to know if the decline continued even after people stopped smoking. To do that they looked at data from members of the Dunedin study which included over one thousand New Zealanders who were followed from birth to age 38. Cannabis usage was included in the study as well as intelligence, memory and attention periodically throughout their lives.
Decline in IQ occurs and never recovers
Heavy and regular users suffered neuropsychological decline across all domains of functioning. Even after stopping, the decline in IQ persisted. The decline was most pronounced among those who started smoking earlier.
Early intervention and education needed
“Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents,” the authors concluded in their report published in the Proceedings of the National Academies of Sciences.