Prenatal Exposure To Alcohol and Pot Have Different Effects on Visual Cortex

Professor Benjamin Thompson PhD School of Optometry and Vision Science Faculty of Science, University of Waterloo Waterloo, Ontario Canada

Dr. Thompson Interview with:
Professor Benjamin Thompson PhD
School of Optometry and Vision Science
Faculty of Science, University of Waterloo
Waterloo, Ontario

Medical Research: What is the background for this study?

Dr. Thompson: Our investigation was part of the longitudinal Infant Development and Environment and Lifestyle (IDEAL) study that was designed to investigate the effect of prenatal methamphetamine exposure on neurodevelopment. Although the negative impact of prenatal drug exposure on a wide range of neurodevelopmental outcomes such cognitive and motor function is established, the effect on vision is not well understood. To address this issue, vision testing was conducted when children in the New Zealand arm of the IDEAL study turned four and half years of age.

Although the primary focus of the IDEAL study was the impact of methamphetamine on neurodevelopment, the majority of children enrolled in the study were exposed to a range of different drugs prenatally including marijuana, nicotine and alcohol. Many children were exposed to multiple drugs. This allowed us to investigate the impact of individual drugs and their combination on the children’s visual development.

Alongside standard clinical vision tests such as visual acuity (the ‘sharpness’ of vision) and stereopsis (3D vision), we also tested the children’s ability to process complex moving patterns. This test, known as global motion perception, targets a specific network of higher-level visual areas in the brain that are thought to be particularly vulnerable to neurodevelopmental risk factors.

Medical Research: What are the main findings?

Dr. Thompson: In agreement with previous studies, we found that prenatal alcohol exposure impaired motion processing in children. Surprisingly prenatal marijuana exposure enhanced motion processing. Perhaps most importantly, the effect of marijuana exposure appeared to cancel out the motion processing deficits associated with alcohol exposure. Nicotine and methamphetamine did not influence motion processing. In addition, visual acuity and stereopsis were not affected by any of the drugs. This suggests that standard clinical tests were not able to detect drug effects in the group of children that we studied.

Medical Research: What should clinicians and patients take away from your report?

Dr. Thompson: Our key finding is that prenatal drug exposure does affect the development of visual brain areas. In particular, drugs such as marijuana and alcohol are not benign and do alter the way in which brain areas function.

Our results should in no way be interpreted as supporting the use of marijuana in pregnancy. The effect we observed was for a very specific visual ability and a large number of other studies have documented negative effects of prenatal marijuana exposure on brain development. However, our results do provide a foundation for new studies designed to investigate the mechanisms underlying the effect of prenatal marijuana exposure on brain development.

Finally, our results demonstrate the importance of considering interactions between different substances in studies of prenatal drug exposure. In our sample the majority of children were exposed to more than one drug.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Thompson: Independent replication of our results would be an important step in progressing this line of research. Furthermore, the use of neuroimaging techniques to investigate the impact of prenatal marijuana and alcohol exposure on visual cortex structure and function would greatly advance our understanding of the mechanisms underlying the effects we report.

Finally, our initial finding that marijuana exposure may neutralize the negative effect of alcohol exposure on global motion perception is worthy of further investigation. If similar effects are found for other measures of neurodevelopment, this might lead to new ways of ameliorating the impact of prenatal alcohol exposure on brain development.


Arijit Chakraborty, Nicola S. Anstice, Robert J. Jacobs, Linda L. LaGasse, Barry M. Lester, Trecia A. Wouldes, Benjamin Thompson. Prenatal exposure to recreational drugs affects global motion perception in preschool children. Scientific Reports, 2015; 5: 16921 DOI:1038/srep16921

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Professor Benjamin Thompson PhD (2015). Prenatal Exposure To Alcohol and Pot Have Different Effects on Visual Cortex

Last Updated on November 28, 2015 by Marie Benz MD FAAD