The researchers didn't find the same IQ dip for people who became frequent users of pot after 18. Although experts said the new findings are not definitive, they do fit in with earlier signs that the drug is especially harmful to the developing brain.
The study is being pushed hard by a group named—move over, all other cliches—"But What About the Children." I gotta admit, for an organization with a name that is literally an anti-drug talking point, they seem weirdly resigned to pot's eventual legality. Their slogan is, "Demand that policymakers who legalize marijuana guarantee the drug will not be marketed to children, like alcohol and tobacco are." Seems fair.
Funding for the study itself and But What About the Children's parent organization, National Families in Action, came in part by the federal government's National Institute on Drug Abuse... which is more or less in the business of warning people about the dangers of drugs. All that said, don't do drugs, kids. Look what happened to us.