Story highlights Marijuana use is increasingly common among adolescents and young adults in the United States

A recent study found current marijuana use was associated with poorer verbal memory and processing speed

(CNN) People who smoked weed regularly as teenagers remembered fewer words as they entered middle age, according to a new study published online by JAMA Internal Medicine.

Marijuana use is increasingly common among adolescents and young adults in the United States. In fact, a recent survey of high school students found more teens use marijuana than tobacco. One reason: a perception that it's not harmful

For this study, researchers randomly selected more than 5,000 young adults from 18 and 30 and followed up with them at varying points over 25 years. At the end of the 25 years, there were more than 3,400 participants still in the study. Their cognitive function was measured using standardized tests of verbal memory, processing speed and executive function.

They found current marijuana use was associated with poorer verbal memory and processing speed, and lifetime exposure to marijuana was associated with worse performance in all three areas of cognitive function. Although past exposure to marijuana was associated with worse verbal memory, it does not appear to affect other domains of cognitive function.

It is unclear whether there are long-term effects on memory from occasional marijuana use earlier in life and whether there is an impact on other areas of cognitive function.

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