Prenatal marijuana exposure contributes to the prediction of marijuana use at age 14.

AIM To evaluate the effects of prenatal marijuana exposure (PME) on the age of onset and frequency of marijuana use while controlling for identified confounds of early marijuana use among 14-year-olds. DESIGN In this longitudinal cohort study, women were recruited in their fourth prenatal month. Women and children were followed throughout pregnancy and at multiple time-points into adolescence. SETTING AND PARTICIPANTS Recruitment was from a hospital-based prenatal clinic. The women ranged in age from 18 to 42, half were African American and half Caucasian, and most were of lower socio-economic status. The women were generally light to moderate substance users during pregnancy and subsequently. At 14 years, 580 of the 763 offspring-mother pairs (76%) were assessed. A total of 563 pairs (74%) was included in this analysis. MEASUREMENTS Socio-demographic, environmental, psychological, behavioral, biological and developmental factors were assessed. Outcomes were age of onset and frequency of marijuana use at age 14. PME predicted age of onset and frequency of marijuana use among the 14-year-old offspring. This finding was significant after controlling for other variables including the child's current alcohol and tobacco use, pubertal stage, sexual activity, delinquency, peer drug use, family history of drug abuse and characteristics of the home environment including parental depression, current drug use and strictness/supervision. CONCLUSIONS Prenatal exposure to marijuana, in addition to other factors, is a significant predictor of marijuana use at age 14.