Marijuana is one of the most commonly used psychoactive substances in society, mainly among youths. Its use has been consistently associated with several health problems, many of which have in common an impairment in the cognitive processes of behavior, including the memory, attention, emotion and decision making. There is evidence suggesting that cannabinoids, marijuana's primary psychoactive substance, have a negative effect in short-term memory, working memory, and decision making. It has also been found that cannabinoids affect attention and the interaction between cognitive events and emotion. This information can be used as an argument of biological plausibility to assess clinical and epidemiological research findings that show that marijuanás use is associated to problems such as traffic accidents, psychosis, depression and poor academic records, among others.