One of the reasons marijuana can be so harmful to the brain is because people tend to start to use it at a young age, like adolescence, when the brain is not fully formed and is still maturing (Agosti, Nunes & Levin, 2002). This early drug use can lead to the abuse of other drugs, but it can also have lasting affects on the brain and the way it functions, because it hits the brain before the brain is ready for drug use. Because marijuana and other illegal drugs are also usually very addicting, they create an urge in the user to continue using them, and so dependence on them can grow, adding to the problem of long-term damage.
There is another problem associated with brain function and marijuana use. Authors Agosti et al. note, "Longitudinal studies have also found a significant association between chronic cannabis use, mental disorders, and social morbidity" (Agosti et al., 2002). Therefore, use of marijuana, especially early use, can ultimately lead to the use of more dangerous drugs, and chronic use can lead to many mental problems. Unfortunately, studies show that marijuana is the most popular illegal drug in use in America today, and that 81% of illegal drug users use marijuana (Trevino & Richard, 2002). What this means for the brains of these users is that they will show additional memory loss, confusion, and other signs of brain damage as their life progresses, especially if they continue to use the drug throughout their lives. It can even lead to mental disorders and death as previously noted. Thus, marijuana is more dangerous than many people believe.
Many proponents of marijuana believe that it should be legalized, but about 55% of the American population is against legalizing the drug (Trevino & Richard, 2002). Proponents of the drug cite many studies that have not shown any damaging affects of the drug, but these studies have consistently been disproved by more effective studies such as those cited here. There will always be a segment of the population that wants to legalize marijuana, especially those who use it for its claimed medicinal affects. However, scientific studies show that marijuana use is harmful to the brain and to the overall health of the user,