A new study led by researchers from the University of Colorado School of Medicine compares adolescent siblings to determine the impact of early and frequent use of marijuana on cognitive function.
This study, published in the journal Addiction, contrasts with previous studies by finding that moderate adolescent cannabis use may have adverse effects that cannot be explained by the genetic or environmental factors that siblings may have in common.
"We wanted to expand our understanding of whether cannabis use is related to lower cognitive functioning," said lead author Jarrod M. Ellingson, Ph.D., assistant professor of psychiatry at the CU School of Medicine. "There's a large body of evidence that cannabis use is linked to cognitive functioning, but we know that cannabis use is not isolated from other important risk factors. That was the primary motivation behind this study, in which we compared siblings to account for many of these risk factors."
Such possibilities include environmental risk factors, such as peer group influence, parental behavior, and socioeconomic status. In addition, by designing the study to look at siblings, researchers could consider whether genetic factors explain a shared risk for worse cognitive functioning and earlier or heavier cannabis use.
With this study, Ellingson and his colleagues were able to establish comparisons between siblings and then determine that differential levels of cannabis use were related to poorer cognitive functioning, particularly verbal memory.
In the article, Ellingson and his co-authors state, "Due to changes in the legality of recreational and medical cannabis and widespread access in many states, valid empirical data must be available to inform policy and public health decisions, including how cannabis use may affect the developing brain."