 The most commonly used illicit drug in the U.S.  95 million Americans, ages 12 or older have at least tried marijuana at some point.  ¾ illicit drug users claim to have used marijuana at least once within the past 30 days

 Main chemical = THC  Effects:  Some painkilling effects  Relaxation  Increased heart rate  Lowered blood pressure  Impairment of short-term and working memory  Coordination  Concentration

 A 2008 study by the University of Melbourne of 15 heavy marijuana users (consuming at least 5 marijuana cigarettes daily for on average 20 years) and 16 controls found:  Average size difference for the smokers in the hippocampus (12 percent smaller) and the amygdala (7 percent smaller).

 Hippocampus = Responsible for creating and storing memories (learning)  Amygdala = processing memory and emotional reactions

 A 2008 study at Karolinska Institute suggested that young rats treated with THC received an increased motivation for drug use, heroin in the study, under conditions of stress.

 Definition of a “gateway drug”  a habit-forming drug that in many cases may lead to the use of other addictive drugs

 Regular marijuana use has been shown to be associated with other long-term problems, including:  poor academic performance  poor job performance  increased absences from work  cognitive problems  lung damage