More than 94 million Americans have tried marijuana at least once, and it remains the most widely used illicit drug in the nation (Johnston et al., 2005). When smoked, the main active ingredient in marijuana, Δ9 -tetrahydrocannabinol (THC) binds to CB-1 cannabinoid receptors in the brain, resulting in a variety of subjective experiences including mood changes, heightened sensitivity to external stimuli, relaxation, and altered perception of time and space (Gobbi et al., 2005; Hollister, 1986). Furthermore, endogenous cannabinoids have been shown to regulate a variety of emotional responses, including anxiety, mood control, and aggression (Martin et al., 2002). CB-1 receptors, the predominant cannabinoid receptor type within the central nervous system (CNS), have been shown to mediate the effects of both endogenous and exogenous cannabinoids, including effects on mood (Chaperon and Thiebot, 1999). CB-1 receptors are abundant within the cerebellum, basal ganglia, cingulate cortex, amygdala, and hippocampus (Witkin et al., 2005), and autoradiographic studies have demonstrated high densities of CB-1 receptors in the frontal cortex, reported to be nearly twice as high as those found in the posterior occipital cortex (Herkenham
