Cannabinoids and drug addiction

Cannabis is the most commonly abused illegal drug in the world and its main psychoactive ingredient, delta-9-tetrahydrocannabinol (THC), produces rewarding effects in animals and humans. Over the past years, the endocannabinoid system has received increasing attention due to the wide spectrum of physiological functions in which it plays a modulating role. Growing evidence is emerging on a possible participation of the endogenous cannabinoid system in the brain reward processes and addictive behaviors. In the present chapter, we will review the most recent findings on the relationship between the endocannabinoid system and drug abuse, addiction, and relapse phenomena. We will first provide a brief overview of the different aspects of the drug addiction cycle, and then summarize what is known about the moderating effects of endocannabinoids in human drug use, abuse, and dependence. For each class of abused drugs, the conspicuous progress made in defining the role of the endocannabinoid system in drug-taking and drug-seeking behaviors will be examined.