Marijuana use at youth is a serious problem in many countries. Since it has strong dependency, many people feel difficult to quit it with all their effort. Some people become psychotic due to its toxic effects. Marijuana use is prohibited in most countries, but there are several black market to deal with it. A large amount of money is circulating in antisocial activists and Marijuana users.
Marijuana is believed as harmful to human body. However, the content and degree of its risk are still unclear. In the past, exposure of Marijuana at the early age was considered to decline your intelligence. However, this idea is challenged by recent studies.
Newser: Study: Pot Doesn't Make Teens Stupid
The relationship between Marijuana use and lowered intelligence has been controversial. Previous studies said that people who had been indulged in Marijuana in their adolescent had poor performance in cognitive function. But, this fact cannot prove the causality that Marijuana does damage to your brain. Another possible explanation is that people being inclined to Marijuana are not smart before adolescent.
The Washington Post: Scientists have found that smoking weed does not make you stupid after all
The present study is a strong antidote against the hypothesis that Marijuana makes you stupid. In this study, identical twins participated in the cohort. Thus, we need not consider the generic factors as influencing the results. Marijuana users had lowered performance in the IQ examination compared to abstinent people. However, there was no significant difference in the IQ between Marijuana using twins and abstinent siblings. These findings should be interpreted as some confounders other than Marijuana are attributable to the difference in the intellectual ability, according to the authors.
PNAS: Impact of adolescent marijuana use on intelligence: Results from two longitudinal twin studies
This study is well structured, and seems to have high reliability. It is likely that Marijuana itself has no effect on the human intelligence.
However, Marijuana has several problematic features. It gets rid of our motivation. Some people become psychotic, and these symptoms are sometimes irreversible. There is a controversy which is more harmful Marijuana and alcohol. In my opinion, Marijuana is riskier.
In a few countries, the regulation of Marijuana is going to be relaxed. This result is advantageous for whom being willing to legalize Marijuana use. Nonetheless, it should be cautious for us to try this drug, I think.