Here we share a timely PLOS Science Wednesday discussion of relevance to the PLOS Neuro Community from our weekly PLOS Science Wednesday AMAs with PLOS-published researchers. An introduction by featured PLOS ONE authors — Shashwath Meda and Godfrey Pearlson, follows, along with the most popular question and answer from their AMA, and a link to the entire discussion which took place today 4/19. –PLOSBLOGS
My name is Shashwath Meda and I am a Senior Clinical Research Associate at Olin Neuropsychiatry, Hartford Hospital/Institute of Living. I am also joined by Dr. Godfrey Pearlson who is the Director of Olin Neuropsychiatry and a Professor of Psychiatry at Yale University. A primary component of our research here at the center focuses on studying the effects of substance use on brain cognition and function.
We recently published a study titled Longitudinal influence of alcohol and marijuana use on academic performance in college students in PLOS ONE. In this study, we evaluated the combined effects of alcohol and marijuana on academic GPA in 1142 freshman college students who were followed up longitudinally over a two-year time period. During this period, each month we collected data on their alcohol and marijuana use patterns while in college through a secure self-report website. In analyzing these data, we identified three substance-use groups, a) a group that used either no or very low amounts of both alcohol and marijuana, b) students that used no/low marijuana but medium-high amounts of alcohol and c) students that consumed medium-high quantities of both substances. Interestingly, we found almost no one that consumed no-low alcohol but high amounts of marijuana.
Our findings show that despite students having the same pre-baseline academic achievement as measured using the SAT scores, at the end of incoming semester those who heavily used either alcohol or alcohol+MJ had a significantly lower GPA compared to those who abstained or had very little of it. We also noticed that students who consumed fairly large quantities of alcohol alone (very little MJ) did not have a consistent decrease in GPA across the two-year period (we only noticed a significant decrease in GPA for the incoming semester). Finally, our follow up analysis suggested that those who moderated drug use over the period of the study could recover and perform better academically.
Hi Shashwatch, thanks for doing this AMA it’s a great topic.
So the elephant in the room for any of these sorts of longitudinal studies is 3rd variables. For instance, it’s quite easy to make an argument that there could be personality or emotional or experiential differences that make someone more likely to consume alcohol and marijuana but also likely to decline in achievement. Do you think this is indeed a causal relationship whereby the combination of alcohol and weed is affecting cognitive ability?
Author SM: Hello – Thanks for the question. What you say is absolutely possible, however as we explicitly indicate in our paper, the analysis that we did just wasn’t geared towards examining any causality. We tried to somewhat alleviate effects of intermediate variables by controlling for baseline measured personality and emotional traits. However to properly investigate what you allude to requires a causal modelling analysis such as SEM etc. We plan on doing this in the near future at least on the baseline variables to see what the data shows us. Again this is just the tip of the iceberg, much more to come in the future years!
Read the complete AMA here: