In-utero cannabis exposure and long-term psychiatric and neurodevelopmental outcomes: The limitations of existing literature and recommendations for future research.

Given increases in cannabis use in pregnancy and animal model research showing effects of in-utero cannabis exposure, high-quality information on long-term consequences of in-utero cannabis exposure in humans is needed. While reviews have summarized findings from observational studies with humans, reviews have not focused on limitations of these studies and recommendations for future research. Therefore, we critically reviewed observational research on in-utero cannabis exposure and psychiatric and neurodevelopmental outcomes measured at or after age 3 and provided recommendations for future research. We used Web of Science, Google Scholar, and work cited from relevant identified publications to identify 46 papers to include in our review. Our review includes two main sections. The first section highlights the extensive limitations of the existing research, which include small and nongeneralizable samples, reliance on self-reported data, lack of detail on timing and amount of exposure, inclusion of older exposure data only, not accounting for important confounders, inclusion of potential mediators as covariates, not including outcome severity measures, and not assessing for offspring sex differences. The second section provides recommendations for future research regarding exposure and outcome measures, sample selection, confounder adjustment, and other methodological considerations. For example, with regard to exposure definition, we recommend that studies quantify the amount of cannabis exposure, evaluate the influence of timing of exposure, and incorporate biological measures (e.g., urine toxicology measures). Given that high-quality information on long-term consequences of in-utero cannabis exposure in humans does not yet exit, it is crucial for future research to address the limitations we have identified.