Marijuana is the most widely used illicit drug. While the scientific literature does find possible theoretical applications for cannabis in the clinical practice, it also uncovers some worrisome dangers surrounding the use of the drug. Besides the respiratory problems associated with the smoking route of administration, it has been found that cannabis use is related to neuropsychiatric and cerebrovascular complications. We conducted a review of the harmful neurological and behavioral consequences related to cannabis use, focusing on adolescence. Given the likelihood of risk during teenage years when the dangerous effects of cannabis are more pronounced, we believe that the population should be properly guided and instructed about the risks of marijuana use, especially the more vulnerable age groups such as teens.