Yet Another Study Finds That Cannabis Use Is Not Independently Linked With IQ Decline

 Photo Credit: NORML

Photo Credit: NORML

Some patients may desire the use of cannabis therapy for symptom management, but may fear its use will have a negative impact. Throughout years of cannabis prohibition, the plant has earned the reputation of harming one’s IQ, but yet another study has come out confirming cannabis does not produce such an impact. Longitudinal data published in the journal Addiction suggests cannabis use by teens is not independently associated with adverse changes in intelligence quotient or executive functioning. Investigators from the U.S. and the U.K. looked at whether or not marijuana use changed neuropsychological performance in a cohort of adolescent twins, and found cannabis use did not negatively impact the adolescent's’ cognitive performance. Rather, there was a negative impact due to “family background factors.”

They explained, “[W]e found that youth who used cannabis … had lower IQ at age 18, but there was little evidence that cannabis use was associated with IQ decline from age 12 to 18. Moreover, although cannabis use was associated with lower IQ and poorer executive functions at age 18, these associations were generally not apparent within pairs of twins from the same family, suggesting that family background factors explain why adolescents who use cannabis perform worse on IQ and executive function tests… Short-term cannabis use in adolescence does not appear to cause IQ decline or impair executive functions, even when cannabis use reaches the level of dependence.”

These findings support previous studies that found cannabis use in adolescence does not have a negative impact on intelligence. This information has been provided by NORML and approved by our Chief Medical Officer.