Undergraduate Honors Theses

Thesis Defended

Spring 2015

Document Type


Type of Thesis

Departmental Honors


Psychology & Neuroscience

First Advisor

Dr. Marie Banich, Professor

Second Advisor

Dr. Joseph Orr, PhD

Third Advisor

Dr. Jerry Rudy, Professor

Fourth Advisor

Dr. David Meyer, Professor


The legalization of marijuana use is a growing social and political issue; it is thus becoming increasingly important to ascertain the effects of marijuana use on the brain. As metrics of brain morphometry are often used to quantify the effects of drug use, this study analyzed the structural MRI data collected by the Human Connectome Project (HCP) of a large population of adults (n=438) for volume and shape changes in the amygdala, hippocampus, and nucleus accumbens associated with duration of marijuana use, age of first marijuana use, or number of lifetime marijuana use episodes. Tobacco use, alcohol abuse, age, and gender were considered as covariates. Of the three marijuana use metrics, only duration of use was found to correlate with significant morphology changes, seen as shape deflections in the left amygdala, right hippocampus, and left nucleus accumbens. These results suggest that marijuana does have an impact on subcortical morphology, but only in terms of duration of use.