“…Chronic marijuana users exhibited a 20% decrease in cortical CB1 receptors compared to controls at baseline, but after a month of abstinence from marijuana, differences were no longer detectable between users and controls (Hirvonen et al, 2012). In animal models, there is an inverse relationship between CB1 receptor expression in cortical and striatal regions, such that striatal regions with more CB1 receptor expression receive input from cortical regions with less expression, and critically, the expression levels of CB1 receptors in these circuits decrease from adolescence to adulthood (Van Waes, Beverley, Siman, Tseng, & Steiner, 2012; Verdurand et al, 2011). Thus, exogenous influences of THC on these circuits could counteract typical maturational trajectories and yield changes in regions critical for decision making and addiction processes (Volkow & Baler, 2014; Volkow, Koob, & McLellan, 2016).…”