The Cerebellum, THC, and Cannabis Addiction: Findings from Animal and Human Studies.

Cannabis is the third most used psychoactive drug worldwide. Despite being legally scheduled as a drug with high harm potential and no therapeutic utility in countries like the USA, evidence shows otherwise and legislative changes and reinterpretations of existing ambiguous laws make this drug increasingly available by legal means. Nevertheless, this substance is able to generate clear addiction syndromes in some individuals who use it, which are accompanied by brain alterations resembling those caused by other addictive drugs. Moreover, there is no available pharmacological treatment for this disorder. This fact motivates a deep study and comprehension of the neural basis of addiction-relevant cannabinoid effects. Interestingly, the cerebellum, a hindbrain structure which involvement in functions not related to motor control and planning is being increasingly recognized in the last decades, seems to be involved in the effects of addictive drugs and addiction-related processes and also presents a high density of cannabinoid receptors. Preclinical research on the involvement of the cerebellum in cannabis' effects has focused in the drug's motor incoordinating actions, potentially underestimating its participation in addiction. Therefore, this review addresses the studies reporting cerebellar involvement in cannabis effects both in experimental animals and human subjects and the possible relevance of these changes for addiction. Additionally, future experimental approaches will be proposed and hopefully this work will stimulate research on the cerebellum in cannabis addiction and help recognizing it as an important part of the neural circuitry affected in cannabis-related disorders.