Teen marijuana use may lower IQ later in life.
Heavy use of marijuana (cannabis), especially when started in the teen years, has been linked to measureable declines in IQ by age 38. New Zealand researchers analyzed data on IQ testing and cannabis dependence diagnoses in 874 individuals. While measurable, the effect was not as marked in those who started heavy cannibis use in adulthood. These findings held true when participants who smoked, consumed alcohol, or used illicit drugs were excluded.
PositiveTip: To help preserve your IQ, avoid the use of marijuana.