20 Aug Up to 70% of Marijuana Users Also Use Tobacco With Complex Results

MedicalResearch.com Interview with:
Francesca M. Filbey PhD
School of Behavioral and Brain Sciences
Center for Brain Health University of Texas at Dallas
Dallas, TX

Medical Research: What is the background for this study? What are the main findings?

Dr. Filbey: Most studies exclude tobacco users from participating, but 70% of marijuana users also use tobacco. We were interested in investigating the combined effects of marijuana and tobacco. Our research targeted the hippocampus because smaller hippocampal size is associated with marijuana use. We chose to study short term memory because the hippocampus is an area of the brain associated with memory and learning. The main finding was surprising. The smaller the hippocampus in the marijuana plus nicotine user, the greater the memory performance. We expected the opposite, which was true of the non-using control group.

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

Dr. Filbey: It is important to note that substances interact with each other, and, therefore, combined use could lead to complex effects.  More research needs to be done to fully understand the effects of marijuana on the brain. Very rarely are individuals using one type of substance and it is very difficult to generalize findings from these studies across the board. It is hard to know what the effects are of marijuana, for instance, if we don’t take into account other substance use such as tobacco.

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

Dr. Filbey: Future studies should consider directly examining the combined effects of these highly prevalently co-used substances.  More research is also needed to further characterize the relationship between the hippocampus and memory in combined users – for instance brain connectivity, and the role of other brain regions such as the prefrontal cortex.

Citation:

Francesca M. Filbey, Tim McQueeny, Shrinath Kadamangudi, Collette Bice, Ariel Ketcherside. Combined effects of marijuana and nicotine on memory performance and hippocampal volume. Behavioural Brain Research, 2015; 293: 46 DOI: 10.1016/j.bbr.2015.07.029

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Francesca M. Filbey PhD (2015). Up to 70% of Marijuana Users Also Use Tobacco With Complex Results

Last Updated on August 20, 2015 by Marie Benz MD FAAD