Prenatal exposure to cannabis linked to lower intelligence in school-aged children

A recent study has shown that prenatal marijuana use has lasting detrimental effects on the developing foetus as demonstrated by lower intelligence test scores in school-age children. Animal studies in rodents have shown that cannabinoid exposure during gestation disrupts the development of the brain affecting motor and cognitive behaviour. The current study sought to examine the effects of prenatal marijuana exposure on the intelligence of children aged 6 years. A total of 648 6-year-old children of mothers who were light-to-moderate users — defined as less than one marijuana cigarette per day — at 4 and 7 months of pregnancy and at delivery were included in the prospective study. The children were assessed with the Stanford-Binet Intelligence Scale (SBIS), and multiple regression analyses were used to examine the effects of prenatal exposure on the children’s intelligence. The results showed a link between prenatal marijuana use and intelligence. Children who were exposed to one or more marijuana cigarettes per day had lower intelligence test scores at age 6 years than their non-exposed counterparts. The average SBIS composite scores among the offspring of current abstainers, light-to-moderate users, and heavy users were 92.0, 90.1, and 90.7, respectively (p=0.4). Heavy use exposure during the first trimester was associated with deficits in verbal reasoning (SBIS deficit of 2.6 points), exposure during the second trimester was associated with deficits in the composite of short-term memory subscale (regression analysis coefficient —4.5) and quantitative reasoning (SBIS deficit of 8 points), while exposure during the third trimester was also associated with deficits in quantitative reasoning (SBIS deficit of 5 points). “The large sample size in the Maternal Health Practices and Child Development study provided adequate statistical power to detect even small effects of prenatal marijuana exposure on the SBIS, while controlling for prenatal exposure to other drugs such as alcohol, tobacco, and cocaine and for the social and environmental factors,” the authors clarified. The authors concluded that prenatal exposure to marijuana has a significantly negative effect on children which is evident at age 6. Reference...