Duke University researchers say there's evidence that early marijuana use has a negative impact on intelligence. examined routine cannabis users who began smoking before the age of 18. On average, subjects showed an 8-point drop in I-Q when measured at age 13 and then again at 38. Madeline Meier worked on the study and says that drop is significant.
Madeline Meier: An average person has an IQ of 100 which places them in the 50th percentile for intelligence compared to their same age peers. And if this average person losses 8 IQ points, bringing them down to an IQ of 92, that drops them from the 50th to the 29th percentile for intelligence.
Meier says that can affect things like memory, problem solving and the ability to acquire knowledge. She says further study is needed to determine how much marijuana causes the impairment.
