![]() Although the overall size of the brain does not change substantially beyond early childhood ( Pfefferbaum et al., 1994), longitudinal morphometric studies reveal global cortical development through middle adolescence ( Giedd et al., 1999 Gogtay et al., 2004) with pruning of superfluous synaptic connections and reductions in glial cells ( Huttenlocher & Dabholkar, 1997 Paus, Keshavan, & Giedd, 2008 Tamnes et al., 2010). Changes to micro- and macrostructure are occurring, particularly in the prefrontal cortex, limbic system, and white matter association fibers, accompanied by neurochemical alterations ( Bava & Tapert, 2010 Huttenlocher & Dabholkar, 1997 Sowell et al., 1999). Females develop tolerance more rapidly than males ( Cocchetto, Owens, Perez-Reyes, DiGuiseppi, & Miller, 1981 Narimatsu, Watanabe, Yamamoto, & Yoshimura, 1991), experience greater sensitivity to the subjective effects of cannabis intoxication (Cooper & Haney, 2009, 2014), and enter treatment for cannabis use disorders earlier, after fewer years of use, and less cumulative exposure ( Ehlers et al., 2010 Hernandez-Avila, Rounsaville, & Kranzler, 2004 Khan et al., 2013).Īdolescence is a period of profound and dynamic changes throughout the brain. Males are more likely than females to use cannabis and initiate use at an earlier age ( Gfroerer & Epstein, 1999 Pope et al., 2003 SAMHSA, 2014). Also of note, there are sex differences in trajectories of use. The rate of transition from non-problematic to problematic cannabis use may occur more rapidly with cannabis than nicotine or alcohol use ( Lopez-Quintero et al., 2011), although fewer lifetime users of cannabis (9%) progress to dependence compared to tobacco (67%) and alcohol (23% Lopez-Quintero et al., 2011). The lifetime risk for cannabis dependence is 17% (one in six) when use is initiated during teenage years ( Anthony, 2006), approximately 9% when use is initiated in adulthood ( Lopez-Quintero et al., 2011), and 25% to 50% in those who use daily ( Hall, 2009 Hall & Degenhardt, 2009) yet it should be noted that some of these studies involve data that are more than two decades old, and updating is warranted as rates may have changed with the shifting pattern of use over time. ![]() The more prevalent usage of a more potent drug in an era of increasing social acceptance of use is a significant public health concern if such use causes harm.
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