Differential effects on cognitive functioning in 13- to 16-year-olds prenatally exposed to cigarettes and marihuana.

Cognitive performance was examined in 145 thirteen- to sixteen-year-old adolescents for whom prenatal exposure to marihuana and cigarettes had been ascertained. The subjects were from a low-risk, predominantly middle-class sample participating in an ongoing, longitudinal study. The assessment battery included tests of general intelligence, achievement, memory, and aspects of executive functioning (EF).

Current and former marijuana use: preliminary findings of a longitudinal study of effects on IQ in young adults.

Background: Assessing marijuana's impact on intelligence quotient (IQ) has been hampered by a lack of evaluation of subjects before they begin to use this substance. Using data from a group of young people whom we have been following since birth, we examined IQ scores before, during and after cessation of regular marijuana use to determine any impact of the drug on this measure of cognitive function.

Methods: We determined marijuana use for seventy 17- to 20-year-olds through self-reporting and urinalysis.