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Sibling Study Reveals Impact of Heavy Cannnabis Use on Memory Interview with: Interview with: Jarrod Ellingson PhD Assistant Professor Department of Psychiatry Anschutz Medical Campus University of Colorado Denver 

Dr. Ellingson

Jarrod Ellingson PhD
Assistant Professor
Department of Psychiatry
Anschutz Medical Campus
University of Colorado Denver What is the background for this study? What are the main findings?

Response: We know that cannabis use is associated with many negative outcomes, but there could be many of reasons for that. For example, socioeconomic factors and peer influences both affect adolescent cannabis use and poorer cognitive functioning. To account for some of those risk factors, we studied nearly 600 sibling pairs with moderate to heavy cannabis use. We found that, as a person uses more cannabis than their sibling, they tend to have worse memory recall than their sibling. What should readers take away from your report?

Response: These findings suggest that moderate to heavy cannabis use (7-9 days per month in this sample) affects memory functioning, and those effects could not be explained by risk factors shared by siblings. Similar studies have been conducted with light users (1-2 days per month) and have not found any effects. Taken together, these findings suggest that once cannabis use reaches moderate to heavy levels, there may be measurable cognitive effects. What recommendations do you have for future research as a result of this work?

Response: An important caveat to these findings is that these data were collected from 2001 to 2006, before legalization (2014 in Colorado). Legal markets now offer products that are much more potent (80%+ THC) than what was available when these data were collected (6-8% THC in confiscated cannabis). We simply don’t know how the effects in this study translate to much more potent cannabis products now available on legal markets. Understanding the effects of high-potency cannabis products is an important area of future research. Is there anything else you would like to add?

Response: This study was supported by grants from the National Institute on Drug Abuse and the National Institute on Alcohol Abuse and Alcoholism. We have no conflicts of interest to report. 


Ellingson, J. M., Ross, J. M., Winiger, E., Stallings, M. C., Corley, R. P., Friedman, N. P., Hewitt, J. K., Tapert, S. F., Brown, S. A., Wall, T. L., and Hopfer, C. J. (2020) Familial factors may not explain the effect of moderate‐to‐heavy cannabis use on cognitive functioning in adolescents: a sibling‐comparison study. Addiction,


Sep 4, 2020 @ 3:59 pm

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