Conceptual issues in behavioral teratology and their application in determining long-term sequelae of prenatal marihuana exposure

BACKGROUND: Behavioral teratology, particularly as it is applied to the evaluation of cognition and behavior of children beyond the toddler stage, has become an area of burgeoning activity. In the area of drug abuse, children exposed in utero are often at developmental peril because of non-drug pre- and postnatal risk factors that make a causal association between the drug of interest and a behavioral teratogenic outcome increasingly problematic as the child gets older. METHODS: In the first portion of this review, the strategies that behavioral teratologists have undertaken to investigate the putative consequences of in utero exposure are discussed in terms of research design, statistical methods and interpretative approaches. In the second part of the paper, the relatively limited literature dealing with the behavioral teratological consequences of prenatal marihuana exposure, particularly in school age offspring, is reviewed. RESULTS: An emergent theme arising from primarily two longitudinal investigations is that in utero cannabis exposure does not impact upon standardized derived IQ scores but is negatively associated with attentional behavior and visual analysis/hypothesis testing. These findings are interpreted as supporting the hypothesis that, among offspring beyond the toddler stage, prenatal marihuana exposure has a negative influence on aspects of executive function. Executive function is a 'top-down', multifaceted cognitive construct involved in organizing and integrating specific cognitive and output processes over a interval of time and is largely mediated by the late developing, prefrontal region of the brain. CONCLUSIONS: The results and the interpretation of the prenatal marihuana findings are discussed in terms of the behavioral teratogenic effects (or lack of effects) during the various developmental stages of the offspring, the non-unitary nature of executive function, cannabis receptors, and the consequences of chronic marihuana use in the non-pregnant population.