Opioid Reinforcement: What It Is And How It Can Be Modulated By Cannabinoids

Cannabis still remains by far the most used substance worldwide. Legalization of cannabis and cannabis products in many countries, together with the emergence of new synthetic opioids and cannabinoids, is raising concern not only for the risk to develop dependence to the same products but also because the sequential use of these substances (cannabinoids and then opioids) might increase the risk, particularly in vulnerable individuals, to develop opioid dependence with the negative health consequences associated with it. Reasons for this interaction have to be searched in the neurobiological mechanisms of opioids and cannabinoids reinforcement. Although both opioids and cannabinoids act on different endogenous receptors, their action finally converges on the same system, the mesolimbic dopamine system, a key circuit in reward processing. Moreover, given that most of cannabis users are youngster and considering that adolescence is a critical period of brain development, the phenomenon is of great concern not only for the risk of dependence but also for the risk to develop psychiatric disorders.