Adolescents prenatally exposed to marijuana: examination of facets of complex behaviors and comparisons with the influence of in utero cigarettes.

For the purposes of this review, the impact of prenatal exposure to marijuana in adolescent offspring is discussed in the context that the effects may be apparent only when the multifaceted nature of complex behaviors is examined and that such exposure can be distinguished from those of prenatal exposure to cigarettes. The data are derived from adolescents participating in an on going longitudinal study for whom prenatal marijuana and cigarette exposure had been ascertained with the low-risk, predominantly middle-class sample that had been assessed since birth. In this report, cognitive functioning and visual perceptual performance in 9- to 12-year-olds and facets of attention in 13- to 16-year-olds are examined. These three areas of behavior all appear to be affected differentially by maternal use of marijuana or cigarettes. Prenatal cigarette exposure was associated with lowered IQ, poorer impulse control, and poorer performance on tests requiring fundamental aspects of visuoperceptual performance. In contrast, prenatal marijuana did not have a negative impact on IQ or on basic visuoperceptual skills. Rather, in utero exposure to marijuana had an impact on the application of these skills in tasks in problem-solving situations requiring visual integration and analytical skills as well as sustained attention. These differential findings are discussed in terms of cigarette exposure having a "bottom-up" impact and marijuana exposure having a "top-down" impact. The latter is also discussed in terms of prenatal marijuana's negative association with aspects of executive function.