Cannabis and mental health.

Cannabis is currently the most widely consumed illegal drug in both Europe and the United States. Cannabis dependence criteria are defined by the principal diagnostic manuals (DSM-IV and ICD-10), but not cannabis withdrawal syndrome, although cannabis withdrawal produces certain significant symptoms that are beginning to be typified by research. While not all cannabis users present mental health problems, recent reviews point to a greater risk of various mental disorders in cannabis users. The risks are associated with younger age at first use, greater frequency of use or certain personal predispositions. Research has revealed not only alterations in both the psychotic and affective spectra, but also cognitive deterioration and associations between cannabis use and antisocial behavior, use of other illegal drugs and other health risks. Although contaminating factors and the difficulty of accurately assessing the extent and history of cannabis use represent considerable obstacles to progress in this research field, studies carried out in recent years have contributed conclusive findings on the potential risks of cannabis use. The present article reviews the main scientific findings and conclusions with respect to the association between cannabis use and mental health.